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Introduction Tolerance (TOL) and physical dependence (PD) constitute important limitations of opioid therapy. The aim of our study was to validate research tools to investigate TOL and PD and to characterize the interactions between opioid (OR) and cannabinoid (CB) receptors in these processes in the GI tract. Methods TOL was assessed through the comparison of morphine ability to inhibit electrically evoked smooth muscles contractility in the mouse ileum that was previously incubated with/without morphine for 1 h. To evaluate the PD, the ileum was incubated with morphine for 10 min, then challenged with naloxone to induce withdrawal response (WR). The OR/CB interactions were evaluated using mixed agonist (PR-38) and AM-251 (CB1 antagonist). Results The inhibitory effect of morphine on ileal contractions was weaker in tissue incubated with this opioid than in tissue incubated without opioid. The opposite was noted for PR-38. In tissues exposed to morphine, but not to PR-38, naloxone induced a WR. The blockage of CB1 receptors with AM-251 before the addition of PR-38 resulted in a naloxone-induced WR. Conclusion The co-activation of OR and CB reduced development of TOL and PD to opioids in the mouse GI tract and mixed OR/CB agonists are promising alternative to currently used opioid drugs.

Chronic administration of opioids produces physical dependence and opioid-induced hyperalgesia. Users claim the Thai traditional tea “Kratom” and component alkaloid mitragynine ameliorate opioid withdrawal without increased sensitivity to pain. Testing these claims, we assessed the combined Kratom alkaloid extract (KAE) and two individual alkaloids, mitragynine (MG) and the analog mitragynine pseudoindoxyl (MP), evaluating their ability to produce physical dependence and induce hyperalgesia after chronic administration, and as treatments for withdrawal in morphine-dependent subjects. C57BL/6J mice (n=10/drug) were administered repeated saline, or graded, escalating doses of morphine (intraperitoneal; i.p.), Kratom alkaloid extract (orally, p.o.), mitragynine (p.o.) or MP (subcutaneously, s.c.) for five days. Mice treated chronically with morphine, KAE or mitragynine demonstrated significant drug-induced hyperalgesia by day 5 in a 48 °C warm-water tail-withdrawal test. Mice were then administered naloxone (10 mg/kg, s.c.) and tested for opioid withdrawal signs. Kratom alkaloid extract and the two individual alkaloids demonstrated significantly fewer naloxone-precipitated withdrawal signs than morphine-treated mice. Additional C57BL/6J mice made physically-dependent on morphine were then used to test the therapeutic potential of combined KAE, mitragynine or MP given twice daily over the next three days at either a fixed dose or in graded, tapering descending doses. When administered naloxone, mice treated with KAE, mitragynine or MP under either regimen demonstrated significantly fewer signs of precipitated withdrawal than control mice that continued to receive morphine. In conclusion, while retaining some liabilities, Kratom, mitragynine and mitragynine pseudoindoxyl produced significantly less physical dependence and ameliorated precipitated withdrawal in morphine-dependent animals, suggesting some clinical value.

Background and aim: Anxiety is one of the most common psychiatric disorders that lead to the disruption of daily life and also the quality of life. Routine medications have many side effects and cause physical dependence and psychosocial addiction. Diosgenin is a phytosteroid found in a number of herbs. The present study aimed to investigate the anxiolytic-like effect of diosgenin in the maternal separation model in male mice focusing on the role of NMDA receptors. Material and Methods: Maternal separation (MS) paradigm was performed daily (3 h) from postnatal day (PND) 2-14. Male mice were treated with different doses of diosgenin to find effective and sub-effective doses. In the next step, mice were treated with an effective dose of diosgenin plus NMDA and or a sub-effective dose of diosgenin plus ketamine (NMDA antagonist). Valid behavioral tests for the evaluation of anxiety-like behavior were performed. Then, mice were euthanized, the hippocampus was dissected out and gene expression of NMDA receptors (NR2a and NR2b subunits) was assessed. Results: MS provokes anxiety-like behaviors in the open field test (OFT) and elevated plus maze (EPM) test. Diosgenin significantly mitigated the negative effects of MS. Co-administration of NMDA attenuated anxiolyticlike effect of the effective dose of diosgenin, while ketamine potentiated the anxiolytic effect of sub-effective dose of diosgenin. Furthermore, MS increased the expression of the NMDA receptor in the hippocampus which to some extent modulated with diosgenin. Conclusion: Diosignin has an anxiolytic-like effect on MS mice which at least, in part, mediated through NMDA receptors.

Despite similar distribution patterns and intracellular events observed in the nociceptin/ orphanin FQ peptide (NOP) receptor and other opioid receptors, NOP receptor activation displays unique pharmacological profiles. Several researchers have identified a variety of peptide and nonpeptide ligands to determine the functional roles of NOP receptor activation and observed that NOP receptor- related ligands exhibit pain modality-dependent pain processing. Importantly, NOP receptor activation results in anti-nociception and anti-hypersensitivity at the spinal and supraspinal levels regardless of the experimental settings in non-human primates (NHPs). Given that the NOP receptor agonists synergistically enhance mu-opioid peptide (MOP) receptor agonist-induced anti-nociception, it has been hypothesized that dual NOP and MOP receptor agonists may display promising functional properties as analgesics. Accumulating evidence indicates that the mixed NOP/opioid receptor agonists demonstrate favorable functional profiles. In NHP studies, bifunctional NOP/MOP partial agonists (e.g., AT-121, BU08028, and BU10038) exerted potent anti-nociception via NOP and MOP receptor activation; however, dose-limiting adverse effects associated with the MOP receptor activation, including respiratory depression, itch sensation, physical dependence, and abuse liability, were not observed. Moreover, a mixed NOP/opioid receptor agonist, cebranopadol, presented promising outcomes in clinical trials as a novel analgesic. Collectively, the dual agonistic actions on NOP and MOP receptors, with appropriate binding affinities and efficacies, may be a viable strategy to develop innovative and safe analgesics.

Background: Several pharmaceutical treatments for chronic pain caused by osteoarthritis (OA) and chronic low back pain (CLBP) are available or currently under development, each associated with different adverse events (AEs) and efficacy profiles. It is therefore important to understand what trade-offs patients are willing to make when choosing between treatments. Methods: A discrete-choice experiment (DCE) was conducted with 437 adults with chronic pain caused by OA and/or CLBP. Respondents were presented with a series of scenarios and asked to choose between pairs of hypothetical treatments, each defined by six attributes: level of symptom control; risks of heart attack, rapidly progressive osteoarthritis and dependency; frequency and mode of administration and cost. Attributes were based on known profiles of oral nonsteroidal anti-inflammatory drugs, opioids and injected nerve growth factor inhibitors, the last of which were under clinical development at the time of the study. Data were analysed using a latent class (LC) model to explore preference heterogeneity. Results: Overall, respondents considered improving symptom control and reducing risk of physical dependency to be the most important attributes. The LC analysis identified four participant classes: an ‘efficacy-focused’ class (33.7%), a ‘cost-averse’ class (29.4%), a ‘physical-dependence–averse’ class (19.6%) and a ‘needle-averse’ class (17.3%). Subgroup membership was incompletely predicted by participant age and their responses to comprehension questions. Conclusions: Preference heterogeneity across respondents indicates a need for a personalized approach to offering treatment options. Symptom improvement, cost, physical dependence and route of administration might be important to different patients. Significance: Multiple treatment options that differ substantially in terms of efficacy and adverse events are available for the management of chronic pain. With a growing emphasis on a patient-centred care model that incorporates patients’ priorities and values into treatment decisions, there is a need to understand how individuals with chronic musculoskeletal pain balance the benefits and risks of treatment and how treatment priorities vary among individuals. This study was designed to identify patient preferences for different characteristics of treatments for the management of chronic pain and to investigate how preferences differ among respondents.

Objective: Hydrogen sulfide is an endogenous gaseous mediator that has been indicated to have a role in pain mechanisms. In this study, we aimed to detect brain and spinal cord hydrogen sulfide levels during different phases of tolerance and dependence to morphine and to determine the effects of inhibition of endogenous hydrogen sulfide production on the development of tolerance and dependence. Methods: Morphine tolerance and dependence was developed by subcutaneous injection of morphine (10 mg/kg) twice daily for 12 days. Physical dependence was determined by counting the jumps for 20 min, which is a withdrawal symptom occurring after a single dose of naloxone (5 mg/kg) administered intraperitoneally (i.p.). Propargylglycine (30 mg/kg, i.p.), a cystathionine-γ-lyase inhibitor, and hydroxylamine (12.5 mg/kg, i.p.), a cystathionine-β-synthase inhibitor, were used as hydrogen sulfide synthase inhibitors. The tail-flick and hot-plate tests were used to determine the loss of antinociceptive effects of morphine and development of tolerance. Results: It was found that chronic and acute uses of both propargylglycine and hydroxylamine prevented the development of tolerance to morphine, whereas they had no effect on morphine dependence. Chronic and acute administrations of hydrogen sulfide synthase inhibitors did not exert any difference in hydrogen sulfide levels in brain and spinal cords of both morphine-tolerant and -dependent animals. Conclusion: It has been concluded that hydrogen sulfide synthase inhibitors may have utility in preventing morphine tolerance.

SLL-039 (N-cyclopropylmethyl-7α−4′-(N’-benzoyl) amino-phenyl-6,14-endoethano-tetrahydronorthebaine) and SLL-1206 (N-cyclopropylmethyl-7α−3′-(p-methoxybenzyl) amino-phenyl-6,14-endoethano-tetrahydronorthebaine) are two 4,5-epoxymorphinan-based high selective κ receptor agonists that we recently discovered. In the present study we characterized their pharmacological properties in comparison with arylacetamide-based typical κ agonist U50,488H. We showed that both SLL-039 and SLL-1206 produced potent and long-lasting antinociceptive actions in three different rodent models of pain via activation of κ opioid receptor. In hot-plate assay, the antinociceptive potency of SLL-039 and SLL-1206 increased about 11-and 17.3-fold compared to U50,488H and morphine, respectively, with ED(50) values of 0.4 mg/kg. Following repeated administration, SLL-1206, SLL-039, and U50,488H all developed analgesic tolerance tested in hot-plate assay. U50,488H and SLL-039 produced antipruritic effects in a dose-dependent manner, whereas SLL-1206 displayed some antipruritic effects only at very low doses. In addition, SLL-1206 was capable of decreasing morphine-induced physical dependence. More importantly, SLL-039 and SLL-1206 at effective analgesic doses did not cause sedation and conditioned place aversion (CPA), whereas U50,488H did. In comparison with SLL-039, SLL-1206 caused similar antinociceptive responses, but fewer sedation and CPA. In conclusion, our results suggest that SLL-039 and SLL-1206 have potential to be developed as novel analgesic agents, and 4,5-expoxymorphinan scaffold is an attractive structure for the development of selective κ agonists with fewer side effects.

Background: Atorvastatin exerts neuroprotective effects on the treatment of central nervous system disorders. Morphine analgesic tolerance and dependence remain as major concerns in medicine. Nitric oxide (NO) pathway mediates the development of opioid analgesic tolerance and dependence, as well as atorvastatin neuroprotection. Objectives: The present study aimed to assess the possible involvement of the NO/cGMP pathway in the process of the effects of atorvastatin on morphine physical dependence. Methods: Dependence was induced by repetitive injection of morphine sulfate. Naloxone was injected at the dose of 4 mg/kg on the last day of the experiment to assess withdrawal signs. Animals received atorvastatin (1, 5, 10, and 20 mg/kg, orally). Nitric oxide synthase (NOS) inhibitors and ODQ were injected before protective dose of atorvastatin. The gene expression of NOS isoforms was evaluated by real-time PCR. Thereafter, the hippocampal levels of cGMP and nitrite were measured. Results: Treatment with atorvastatin 10 mg/kg significantly attenuated naloxone-induced withdrawal behaviours. The administration of L-NAME, aminoguanidine, and ODQ before atorvastatin enhanced its effects. The treatment with atorvastatin significantly decreased the nitrite and cGMP levels as well as NOS gene expression in the hippocampus of dependent animals. Conclusions: It can be concluded that atorvastatin, possibly, through inducible NOS, could alleviate morphine dependence and withdrawal signs.

Introduction The major aim of this study was to test whether abstinence from e-cigarettes causes withdrawal symptoms in former smokers. Methods We conducted an unblinded, within-participants, pre–post clinical trial in which 109 former smokers who were current daily electronic cigarette (e-cigarette) users used their own e-cigarette for 7 days followed by 6 days of biologically confirmed abstinence engendered via an escalating contingency payment system. Participants monitored symptoms of nicotine withdrawal daily via an Interactive Voice Response system. They also attended three laboratory visits per week for carbon monoxide and cotinine testing to verify abstinence. Results Half of participants completely abstained for a week. All the Diagnostic and Statistical Manual, Fifth Edition (DSM-5) tobacco withdrawal symptoms, craving for e-cigarettes, craving for tobacco cigarettes, and the four possible new withdrawal symptoms (anhedonia, impulsivity, mood swings, and positive affect) increased during abstinence. Weight increased and heart rate decreased with abstinence. Symptoms showed the prototypical inverted U time pattern of a withdrawal state. The magnitude of withdrawal appeared to be somewhat less than that in a prior study of abstinent daily tobacco cigarette smokers. More severe withdrawal on the first 2 days of abstinence did not predict abstinence on the last day of the study. Conclusions Former smokers who are daily e-cigarette users transfer physical dependence on tobacco cigarettes to dependence on e-cigarettes. The severity of withdrawal from e-cigarettes appears to be only somewhat less than that from daily tobacco cigarette use. Replication tests that include placebo controls, testing for pharmacological specificity, and including never-smokers, non-daily e-cigarette users and dual users are indicated. Implications Our results indicate e-cigarettes can maintain physical dependence. This adverse effect should be included in any risk vs. benefit calculation. Also, potential and current e-cigarette users should be informed that abrupt cessation of e-cigarettes can cause withdrawal symptoms. Trial registration NCT02825459.

Morphine is a potent opioid analgesic used to alleviate moderate or severe pain, but the development of drug tolerance and dependence limits its use in pain management. Our previous studies showed that the candidate protein for I1 imidazoline receptor, imidazoline receptor antisera-selected (IRAS)/Nischarin, interacts with μ opioid receptor (MOR) and modulates its trafficking. However, there is no report of the effect of IRAS on morphine tolerance and physical dependence. In the present study, we found that IRAS knockout (KO) mice showed exacerbated analgesic tolerance and physical dependence compared to wild-type (WT) mice by chronic morphine treatment. Chronic morphine treatment down-regulated the expression of MOR in spinal cord of IRAS KO mice, while had no significant effect on MOR expression in WT mice. We observed the compensatory increase of cAMP accumulation in spinal cord after morphine tolerance, and this change was more significant in KO mice than WT mice. Furthermore, KO mice showed more elevation in the phosphorylation of AMPA receptor GluR1-S845 than WT mice, while the total expression of GluR1 remained unchanged after morphine dependence. Altogether, these data suggest that IRAS may play an important role in the development of morphine tolerance and physical dependence in vivo through modulating MOR expression, as well as AMPA GluR1-S845 phosphorylation, which might be one of the mechanisms underlying the development of opiate addiction.

Here, we aimed to investigate the effects of fluoxetine on morphine-induced analgesia, as well as preventive effects of it on morphine induced tolerance and dependence in mice. We also elucidate the involvement of L-type Ca2+ channels in these phenomena. To induce morphine tolerance, mice were treated with morphine (50 mg/kg) for 3 consecutive days. To evaluate the involvement of the calcium channel in the effects of fluoxetine (5, 20 mg/kg), combination ineffective doses of the two L-type calcium channel blockers, nimodipine (5 mg/kg) or diltiazem (20 mg/kg) with flouxetine were used with each morphine dose. Nociceptive behavior was evaluated using hot-plate test, while physical dependence assessed by naloxone-precipitated withdrawal on the fourth day of experiment. The expression of Cav1.2 and Cav1.3 subunits of the L-type calcium channels in cortex and mesolimbic tissues were measured using western immunoassay. Results showed that co-administration of fluoxetine (20 mg/kg) with morphine increased its acute analgesia effect and prevented the induction of morphine antinociceptive tolerance and physical dependence in mice. Moreover, these effects was potentiated by pre-treatment with diltiazem or nimodipine. Results also showed up-regulation of the Cav1.3 and Cav1.2 expression in the cerebral cortex and mesolimbic regions through the development of morphine dependence. Moreover, chronic administration of fluoxetine with morphine reduced the observed up-regulation of Cav1.3 and Cav1.2 expression in cortex and mesolimbic tissues. Our data indicated that co-administering of fluoxetine with morphine could potentiate the antinociceptive effect of morphine, prevent morphine analgesia tolerance and attenuated the morphine withdrawal signs during induction phases. Moreover, we also pointed out for the first time the role of L-type Ca2+ channel channels in the modulatory effects of fluoxetine on the morphine-related effects.

Bulleyaconitine A (BAA), a C19-diterpenoid alkaloid, has been prescribed as a nonnarcotic analgesic to treat chronic pain over four decades in China. The present study investigated its inhibition in morphine-induced withdrawal symptoms, conditioned place preference (CPP) and locomotor sensitization, and then explored the underlying mechanisms of actions. Multiple daily injections of morphine but not BAA up to 300 μg/kg/day into mice evoked naloxone-induced withdrawal symptoms (i.e., shakes, jumps, genital licks, fecal excretion and body weight loss), CPP expression, and locomotor sensitization. Single subcutaneous BAA injection (30–300 μg/kg) dose-dependently and completely attenuated morphine-induced withdrawal symptoms, with ED50 values of 74.4 and 105.8 μg/kg in shakes and body weight loss, respectively. Subcutaneous BAA (300 μg/kg) also totally alleviated morphine-induced CPP acquisition and expression and locomotor sensitization. Furthermore, subcutaneous BAA injection also specifically stimulated dynorphin A expression in microglia but not astrocytes or neurons in nucleus accumbens (NAc) and hippocampal, measured for gene and protein expression and double immunofluorescence staining. In addition, subcutaneous BAA-inhibited morphine-induced withdrawal symptoms and CPP expression were totally blocked by the microglial metabolic inhibitor minocycline, dynorphin A antiserum, or specific KOR antagonist GNTI, given intracerebroventricularly. These results, for the first time, illustrate that BAA attenuates morphine-induced withdrawal symptoms, CPP expression, and locomotor sensitization by stimulation of microglial dynorphin A expression in the brain, suggesting that BAA may be a potential candidate for treatment of opioids-induced physical dependence and addiction.

Background: Caffeine is from methyl xanthine class which mainly stimulates the central nervous system. Caffeine is one of the most widely used psychoactive drugs in the world. It is commonly found in beverages, chocolates, cocoa containing products and in medications. Caffeine is recognized as legal and its consumption is unregulated all over of the world. Objectives: The objective of this study is to summarize the impact of caffeine on behavioral and health alterations, in both controlled and overdose conditions. Moreover, the specifics of caffeine withdrawal and a number of guidelines on how to handle reducing or quitting caffeine intake altogether is also highlighted. Methodology: To compose this review, more than seventy research and review articles were overviewed that were published over a period of last twenty years, using Google Scholar search engines. Results: Caffeine regular use causes physical dependence which may become the caffeine withdrawal sign that can consequently harm normal working. The most important function of caffeine is that it can reversibly blocks the adenosine performance on its receptor and as a result which prevent the beginning of drowsiness encouraged by adenosine. Caffeine also stimulates certain portions of the autonomic nervous system symptom including fatigue, drowsiness, depressed mood, headache, difficulty concentrating, decreased energy, decreased contentedness, decreased alertness, irritability and unclear headed. Conclusion: It is concluded that utilization of caffeine in a prescribed dose can have good impact on health and may decrease addictive symptoms. Additionally, reducing caffeine dosage over a six week period guides to successful, long-term caffeine cessation with very few side effects.

Abuse and misuse of prescription drugs remains an ongoing concern in the USA and worldwide; thus, all centrally active new drugs must be assessed for abuse and dependence potential. Sphingosine-1-phosphate (S1P) receptor modulators are used primarily in the treatment of multiple sclerosis. Among the new S1P receptor modulators, siponimod, ozanimod, and ponesimod have recently been approved in the USA, European Union (EU), and other countries. This review of literature and other public data has been undertaken to assess the potential for abuse of S1P receptor modulators, including ozanimod, siponimod, ponesimod, and fingolimod, as well as several similar compounds in development. The S1P receptor modulators have not shown chemical or pharmacological similarity to known drugs of abuse; have not shown abuse or dependence potential in animal models for subjective effects, reinforcement, or physical dependence; and do not have adverse event profiles demonstrating effects of interest to individuals who abuse drugs (such as sedative, stimulant, mood-elevating, or hallucinogenic effects). In addition, no reports of actual abuse, misuse, or dependence were identified in the scientific literature for fingolimod, which has been on the market since 2010 (USA) and 2011 (EU). Overall, the data suggest that S1P receptor modulators are not associated with significant potential for abuse or dependence, consistent with their unscheduled status in the USA and internationally.

One of the main challenges in contemporary medicinal chemistry is the development of safer analgesics, used in the treatment of pain. Currently, moderate to severe pain is still treated with the “gold standard” opioids whose long-term often leads to severe side effects. With the discovery of biased agonism, the importance of this area of pharmacology has grown exponentially over the past decade. Of these side effects, tolerance, opioid misuse, physical dependence and substance use disorder (SUD) stand out, since these have led to many deaths over the past decades in both USA and Europe. New therapeutic molecules that induce a biased response at the opioid receptors (MOR, DOR, KOR and NOP receptor) are able to circumvent these side effects and, consequently, serve as more advantageous therapies with great promise. The concept of biased signaling extends far beyond the already sizeable field of GPCR pharmacology and covering everything would be vastly outside the scope of this review which consequently covers the biased ligands acting at the opioid family of receptors. The limitation of quantifying bias, however, makes this a controversial subject, where it is dependent on the reference ligand, the equation or the assay used for the quantification. Hence, the major issue in the field of biased ligands remains the translation of the in vitro profiles of biased signaling, with corresponding bias factors to in vivo profiles showing the presence or the lack of specific side effects. This review comprises a comprehensive overview of biased ligands in addition to their bias factors at individual members of the opioid family of receptors, as well as bifunctional ligands.

Physical dependence and addiction differ in that addiction causes activation of certain dopaminergic pathways in the mesolimbic system. Addiction occurs when this reward circuit is stimulated by drugs which are absorbed rapidly into the body, cross blood–brain barrier and for which tolerance develops. Ethanol is a commonly abused drug and causes greater mortality than several chronic diseases combined. Ethanol is a CNS stimulant at initial doses, it causes depression at higher doses, death occurring by coma. Acute withdrawal or delirium tremens can be life threatening and is treated by benzodiazepines. Disulfiram, acamprosate, and naltrexone help sustain abstinence. Methanol toxicity results from accumulation of formic acid and is treated by inhibiting the enzyme aldehyde dehydrogenase. The most addictive agent, nicotine works by stimulating nicotinic cholinergic receptors. To prevent withdrawal, nicotine substitutes such as patches and gums are used. Vaping poses dangers of its own and its entry has been made illegal in India. Varenicline and bupropion help sustain abstinence. Cannabis has been made legal to consume in some countries, given its low chances of causing tolerance and withdrawal. Nabilone and dronabinol are used medically and act on CB1 receptors.

Brassica oleracea L. or Broccoli, is known for its numerous health benefits attributed to the rich array of phytochemicals. Our earlier study showed the hydroalcoholic extract of Broccoli had significant antianxiety activity. The present study involved bioactivity-directed fractionation of the active extract with the aim of separating the constituent responsible for the activity. The bioactive extract was fractionated by column chromatography. The antianxiety activity of the obtained fractions and sub-fractions was evaluated using the elevated plus maze model in mice. It led to the isolation of the bioactive compound. The antianxiety effect was confirmed by hole-board test and mirror chamber test. Structure of the compound was characterized by UV, IR, 1 H NMR, 13 C NMR, MS techniques, and was found to be kaempferol-3-O-β-D-glucoside. The content of kaempferol-3-O-β-D-glucoside in florets of B. oleracea was determined by HPTLC. It was found to be present to the extent of 0.061% w/w. PRACTICAL APPLICATIONS: Anxiety disorders cause immense suffering worldwide and hence search for safe and effective antianxiety drugs has become important area of research. Most commonly and widely prescribed drugs for anxiety that is, benzodiazepines may cause many adverse effects such as drowsiness, confusion, dizziness etc. They also cause physical dependence and withdrawal symptoms. Flavonoids, and their semi-synthetic derivatives, moreover, do not cause any such side effects unlike benzodiazepines. Broccoli or Brassica oleracea is reported to contain a number of flavonoids like quercetin, kaempferol, and their derivatives. In the present investigation, bioactivity-guided isolation showed that the antianxiety activity of B. oleracea is due to kaempferol-3-O-β-D-glucoside, a compound which has been earlier reported to be present in B. oleracea. Hence, after detailed investigation this compound can be developed into a potential antianxiety drug.

Objective Dihydromyricetin (DHM), a natural flavonoid, is used to reduce alcohol hangover. It has a modulatory role on GABAA receptors with significant effects on seizure and anxiety in animal models. We aimed to evaluate the effect of DHM on morphine conditioned place preference (CPP) and withdrawal sings following morphine dependence using animal models. Methods The effect of DHM (1, 2 and 5 mg/kg, intraperitoneal; ip) on the acquisition and expression of morphine-induced CPP was evaluated in male mice. Administration of morphine for three consecutive days induced physical dependence. The withdrawal signs such as jumping and defecation were precipitated by administration of naloxone (8 mg/kg, ip). The effect of DHM on the development of physical dependence was assessed by injection of DHM before morphine administrations. Results DHM, at the dose of 5 mg/kg, reduced expression of morphine CPP with an increase in the locomotor activity. DHM, at the doses of 2 and 5 mg/kg, also reduced development of morphine CPP. DHM alleviated development of morphine-induced physical dependence at the dose of 1, 2, and 5 mg/kg by decreasing jumping and defecation. Conclusion These results indicated that DHM decreased acquisition and expression of morphine CPP and inhibited development of morphine-induced physical dependence.

Butorphanol, a mixed opioid agonist/antagonist, is considered to be a relatively safe drug when used within the therapeutic dose range. However, diversional uses of butorphanol involving high doses have been documented. In the present review, the relative involvement of μ-, δ-, and κ-opioid receptors in butorphanol physical dependence in rats is discussed. Physical dependence was produced by continuous intracerebroventricular (icv) infusion of butorphanol (26 nmol/h) for 72 h in male Sprague-Dawley rats. Multiple icy injections of β-funaltrexaimne (β-FNA, a μ-antagonist, 12, 24, or 48 nmol/5 μl), naltrindole (NTI, a δ-antagonist, 0.1, 1, or 10 nmol/5 μl), or nor-binaltorphimine (nor-BNI, a κ-antagonist, 12, 24, or 48 nmol/5 μl) significantly attenuated the development of butorphanol dependence. Furthermore, icy administration of both NTI (24, 48, or 100 nmol/5 μl) and nor-BNI (3, 10, 20, 48, or 100 nmol/5 μl) precipitated withdrawal behaviors, whereas, β-FNA (12, 24, 48, or 100 nmol/5 μl) was unable to elicit withdrawal signs in butorphanol-dependent rats. The results indicate that the development of butorphanol dependence is due to effects of butorphanol on central μ-, δ-, and κ-opioid receptors.

Tapentadol, an analgesic with a dual mechanism of action, involving both μ-opioid receptor agonism and noradrenaline reuptake inhibition (MOP-NRI), was designed for the treatment of moderate to severe pain. However, the widely acknowledged risk of analgesic tolerance and development of physical dependence following sustained opioid use may hinder their effectiveness. One of the possible mechanisms behind these phenomena are alterations in nitric oxide synthase (NOS) system activity. The aim of the study was to investigate the tolerance and dependence potential of tapentadol in rodent models and to evaluate the possible role of nitric oxide (NO) in these processes. Our study showed that chronic tapentadol treatment resulted in tolerance to its antinociceptive effects to an extent similar to tramadol, but much less than morphine. A single injection of a non-selective NOS inhibitor, NG-nitro-L-arginine (L-NOArg), reversed the tapentadol tolerance. In dependence studies, repeated administration of L-NOArg attenuated naloxone-precipitated withdrawal in tapentadol-treated mice, whereas a single injection of L-NOArg was ineffective. Biochemical analysis revealed that tapentadol decreased nNOS protein levels in the dorsal root ganglia of rats following 31 days of treatment, while no significant changes were found in iNOS and eNOS protein expression. Moreover, pre-treatment with L-NOArg augmented tapentadol antinociception in an opioid- and α2-adrenoceptor-dependent manner. In conclusion, our data suggest that the NOS system plays an important role in the attenuation of tapentadol-induced tolerance and withdrawal. Thus, inhibition of NOS activity can serve as a promising treatment option for long-term tapentadol use by extending its effectiveness and improving the side-effects profile.

AM1710 (3-(1,1-dimethyl-heptyl)-1-hydroxy-9-methoxy-benzo(c) chromen-6-one), a cannabilactone cannabinoid receptor 2 (CB2) agonist, suppresses chemotherapy-induced neuropathic pain in rodents without producing tolerance or unwanted side effects associated with CB1 receptors; however, the signaling profile of AM1710 remains incompletely characterized. It is not known whether AM1710 behaves as a broad-spectrum analgesic and/or suppresses the development of opioid tolerance and physical dependence. In vitro, AM1710 inhibited forskolin-stimulated cAMP production and produced enduring activation of extracellular signal-regulated kinases 1/2 phosphorylation in human embryonic kidney (HEK) cells stably expressing mCB2. Only modest species differences in the signaling profile of AM1710 were observed between HEK cells stably expressing mCB2 and hCB2. In vivo, AM1710 produced a sustained inhibition of paclitaxel-induced allodynia in mice. In paclitaxel-treated mice, a history of AM1710 treatment (5 mg/kg per day × 12 day, i.p.) delayed the development of antinociceptive tolerance to morphine and attenuated morphine-induced physical dependence. AM1710 (10 mg/kg, i.p.) did not precipitate CB1 receptor–mediated withdrawal in mice rendered tolerant to Δ(9)-tetrahydrocannabinol, suggesting that AM1710 is not a functional CB1 antagonist in vivo. Furthermore, AM1710 (1, 3, 10 mg/kg, i.p.) did not suppress established mechanical allodynia induced by complete Freund’s adjuvant (CFA) or by partial sciatic nerve ligation (PSNL). Similarly, prophylactic and chronic dosing with AM1710 (10 mg/kg, i.p.) did not produce antiallodynic efficacy in the CFA model. By contrast, gabapentin suppressed allodynia in both CFA and PSNL models. Our results indicate that AM1710 is not a broad-spectrum analgesic agent in mice and suggest the need to identify signaling pathways underlying CB2 therapeutic efficacy to identify appropriate indications for clinical translation.

Introduction: Past trials of buprenorphine (BUP) in the treatment of major depressive disorder (MDD) have displayed favorable results, although its clinical utility was limited by the risk of abuse or physical dependence. By combining BUP with samidorphan (SAM), the euphoric high is negated by an opposing mechanism, which theoretically reduces addictive-like properties while allowing the antidepressant properties to remain. As such, the objective of this article is to analyze the results of BUP/SAM premarketing clinical trials as adjunctive treatment for treatment-resistant MDD. Methods: A comprehensive PubMed/MEDLINE search was conducted through November 9, 2017, using the following search terms: depression, samidorphan, buprenorphine, ALKS-5461. Additional data were obtained from Clinicaltrials.gov and resources included in the present study. All English-language clinical trials evaluating the combination of BUP/SAM in the treatment of MDD were included. Results: A few premarketing studies have evaluated the efficacy and safety of BUP/SAM combination as adjunctive treatment in patients with treatment-resistant MDD. The FORWARD-1 through FORWARD-5 trials concluded (1) the most effective dosing ratio of BUP/SAM to reduce abuse potential was 1:1; (2) statistically significant changes in scores from baseline on the Montgomery-Asberg Depression Rating Scale were noted for the 2 mg/2 mg dose compared with placebo; and (3) the most commonly reported adverse effects were nausea, dizziness, and fatigue. Discussion: Buprenorphine/samidorphan has shown favorable results for efficacy and tolerability in premarketing studies evaluating its use as adjunctive therapy for treatment-resistant MDD. Its novel mechanism targeting the opioid pathway may serve as a promising antidepressant devoid of abuse potential.

Background Severe pain reduces quality of life of patients with various diseases, often because chronic morphine therapy results in reduced analgesic effectiveness, or tolerance, leading to escalating doses and distressing adverse effects. Nitric oxide (NO) plays a role in morphine tolerance and dependence. Objective Venlafaxine, an antidepressant, is known to modulate nitric oxide (NO) pathway in nervous tissues. In the present study, the effect of systemic venlafaxine (VLF) on the development of morphine tolerance and dependence, acute morphine-induced antinociception, and the probable involvement of the L-arginine/NO/cGMP pathway in these effects were investigated in mice. Methods Animals developed tolerance to the antinociceptive effect of morphine (50 mg/kg, s.c. daily) for 3 consecutive days. NO modulators like L-NAME (NO synthase inhibitor) and L-Arginine (L-Arg, substrate for NO synthase), sildenafil (cGMP-PDE inhibitor) alone or in combination with venlafaxine were used. Results The results showed that i.p. administration of VLF (5-40 mg/kg) produced antinociceptive effect in a dose-dependent way. Pretreatment with L-Arg (200 mg/kg, i.p.) reversed the antinociception and L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.) potentiated the antinociceptive effect. Moreover, co-administration of VLF in non-effective dose (5 mg/kg) with morphine, potentiated acute morphine-induced analgesia (5 mg/kg, s.c.). This effect was antagonized by L-arginine (200 mg/kg, i.p.) and potentiated by L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.). On the other hand, VLF was prevented the development of morphine antinociceptive tolerance and dependence. These effects were antagonized by L-arginine (200 mg/kg, i.p.) and potentiated by L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.). Conclusion Our data suggest that the combination of VLF with morphine may be a relevant therapeutic implication to manage pain even when tolerance to morphine exists. Moreover, our data demonstrates the involvement of L-Arg/NO/cGMP pathway in the prevention of morphine tolerance and dependence by venlafaxine.

The use of opioids for the treatment of pain, while largely effective, is limited by detrimental side effects including analgesic tolerance, physical dependence, and euphoria, which may lead to opioid abuse. Studies have shown that compounds with a μ-opioid receptor (MOR) agonist/δ-opioid receptor (DOR) antagonist profile reduce or eliminate some of these side effects including the development of tolerance and dependence. Herein we report the synthesis and pharmacological evaluation of a series of tetrahydroquinoline-based peptidomimetics with substitutions at the C-8 position. Relative to our lead peptidomimetic with no C-8 substitution, this series affords an increase in DOR affinity and provides greater balance in MOR and DOR binding affinities. Moreover, compounds with carbonyl moieties at C-8 display the desired MOR agonist/DOR antagonist profile whereas alkyl substitutions elicit modest DOR agonism. Several compounds in this series produce a robust antinociceptive effect in vivo and show antinociceptive activity for greater than 2 h after intraperitoneal administration in mice.

Planarians have mammalian-like neurotransmitter systems and have been established as a novel in vivo model for neuropharmacology. In previous research, planarians that have been exposed to the cannabinoid receptor (CB-R) agonist WIN 55,212-2 for 1 h displayed abstinence-induced withdrawal when tested in drug-free, but not in drug-containing, water. The goals of the present study were to extend previous work and to further establish a cannabinoid behavioral model with planarians. The results showed 1) four different CB-R antagonists (AM251, AM281, SLV319 and SR144528) dose-relatedly blocked development of physical dependence induced by two different CB-R agonists (WIN 55,212-2 and JWH251); 2) none of the same four antagonists (AM251, AM281, SLV319 or SR144528) precipitated withdrawal; 3) short wavelength (254 nm), but not long wavelength (366 nm), ultraviolet (UV) light attenuated abstinence-induced withdrawal from WIN 55,212-2, while short wavelength UV light induced moderate withdrawal behavior. The results confirm the use of a planarian model as a simple yet robust way to study development of physical dependence to cannabinoid agonists. The effect of UV irradiation adds to the evidence that the results are receptor-related. The results also give rise to the surprising suggestion, within the limitations of the methodology, that development of cannabinoid physical dependence and antagonist-induced precipitated withdrawal might be separable phenomena in planarians.

Here, we describe the optimization, synthesis, and associated pharmacological analgesic activities of a new series of bifunctional piperidinamide derivatives as sigma-1 receptor (σ1R) antagonists and mu opioid receptor (MOR) agonists. The new compounds were evaluated in vitro in σ1R and MOR binding assays. The most promising compound 114 (also called HKC-126), showed superior affinities for σ1R and MOR and good selectivity to additional receptors related to pain. Compound 114 showed powerful dose-dependent analgesic effects in the acetic acid writhing test, formalin test, hot plate test, and chronic constriction injury (CCI) neuropathic pain model. In contrast to an equianalgesic dose of fentanyl, compound 114 produced fewer opioid-like side effects, such as reward liability, respiratory depression, physical dependence, and sedation. Lastly, the pharmacokinetic properties of this drug were also acceptable, and these results suggest that compound 114, as a mixed σ1R/MOR ligand, has potential for treating neuropathic pain.

The use of morphine and other opioids for chronic pain is limited by the development of analgesic tolerance and physical dependence. Morphine produces its effects by activating the μ opioid receptor, which couples to Gαi/o-containing heterotrimeric G proteins. Evidence suggests that the antinociceptive effects of morphine are mediated by Gαo. However, the role of Gαo in the development of morphine tolerance and dependence is unknown. The objective of the study is to evaluate the contribution of Gαo to the development of morphine tolerance and dependence in mice. 129S6 mice lacking one copy of the Gαo gene (Gαo +/−) were administered morphine acutely or chronically. Mice were examined for tolerance to the antinociceptive action of morphine using the 52 °C hot plate as the nociceptive stimulus and for dependence by evaluating the severity of naltrexone-precipitated withdrawal. Wild-type littermates of the Gαo +/− mice were used as controls. Changes in μ receptor number and function were determined in midbrain and hindbrain homogenates using radioligand binding and μ agonist-stimulated [35S]GTPγS binding, respectively. Following either acute or chronic morphine treatment, all mice developed antinociceptive tolerance and physical dependence, regardless of genotype. With chronic morphine treatment, Gαo +/− mice developed tolerance faster and displayed more severe naltrexone-precipitated withdrawal in some behaviors than did wild-type littermates. Morphine tolerance was not associated with changes in μ receptor number or function in brain homogenates from either wild-type or Gαo +/− mice. These data suggest that the guanine nucleotide binding protein Gαo offers some protection against the development of morphine tolerance and dependence.

[Image: see text] The effects of opioids in the central nervous system (CNS) provide significant benefit in the treatment of pain but can also lead to physical dependence and addiction, which has contributed to a growing opioid epidemic in the United States. Gastrointestinal dysfunction is an additional serious consequence of opioid use, and this can be treated with a localized drug distribution of a non-CNS penetrant, peripherally restricted opioid receptor antagonist. Herein, we describe the application of Theravance’s multivalent approach to drug discovery coupled with a physicochemical property design strategy by which the N-substituted-endo-3-(8-aza-bicyclo[3.2.1]oct-3-yl)-phenyl carboxamide series of μ-opioid receptor antagonists was optimized to afford the orally absorbed, non-CNS penetrant, Phase 3 ready clinical compound axelopran (TD-1211) 19i as a potential treatment for opioid-induced constipation.

Orexin neuropeptides are involved in opiate-induced physical dependence and expression of withdrawal signs following drug abstinence. Orexin type-1 receptors (OXR1) are expressed throughout the rostroventrolateral medulla (RVLM), particularly in the lateral paragigantocellularis (LPGi) nucleus. The present study examined whether blocking OXR1 in LPGi region could affect the development of morphine dependence and so behavioral manifestations induced by morphine withdrawal in rats. Male Wistar rats weighing 250-300 g were used. In order to induce drug dependence, morphine was injected subcutaneously (s.c.) (6, 16, 26, 36, 46, 56, and 66 mg/kg, 2 ml/kg) at an interval of 24 h for 7 days. Animals were divided into experimental groups in which the orexin type-1 receptor antagonist, SB-334867 (0.2 μl, 3 mM), or its vehicle were injected into the LPGi nucleus for 7 days before each morphine injection. On day 8, naloxone (2.5 mg/kg, i.p.) was administered and morphine withdrawal behaviors were monitored for 25 min. Our results indicated that the inhibition of OXR1 in LPGi nucleus significantly reduces the development of morphine dependence and behavioral signs elicited by the administration of naloxone in morphine-dependent rats.

Cebranopadol is a mixed NOP/opioid receptor agonist currently under development as innovative analgesic. In this study the liability of cebranopadol to produce opioid-type physical dependence has been evaluated in comparison with morphine in wild type mice and in mice knockout for the NOP receptor gene (NOP(-/-)). Mice were treated twice a day for 5 days with increasing doses of cebranopadol or morphine (cumulative doses 10.2 and 255 mg/kg, respectively) and the number of jumping in response to naloxone 10 mg/kg were measured after 2 h from the last injection. In wild type mice naloxone evoked a similar withdrawal jumping behavior in animal pretreated with morphine or cebranopadol. In NOP(-/-) mice morphine treatment produced the same signs of withdrawal as in NOP(+/+) animals, while cebranopadol treatment elicited a stronger withdrawal syndrome in NOP(-/-) than of NOP(+/+) mice. These results demonstrated that the activation of the NOP receptor reduces the liability of cebranopadol to produce opioid-like physical dependence. Thus, the simultaneous activation of NOP and opioid receptors can be an effective pharmacological strategy to counteract physical dependence to opioid drugs.

BACKGROUND The chronic intermittent ethanol (CIE) paradigm is valuable for screening compounds for efficacy to reduce drinking traits related to alcohol use disorder (AUD), as it measures alcohol consumption and preference under physical dependence conditions. Air control-treated animals allow simultaneous testing of similarly treated, nondependent animals. As a consequence, we used CIE to test the hypothesis that tigecycline, a semisynthetic tetracycline similar to minocycline and doxycycline, would reduce alcohol consumption regardless of dependence status. METHODS Adult C57BL/6J female and male mice were tested for tigecycline efficacy to reduce ethanol (EtOH) consumption using a standard CIE paradigm. The ability of tigecycline to decrease 2-bottle choice of 15% EtOH (15E) versus water intake in dependent (CIE vapor) and nondependent (air-treated) male and female mice was tested after 4 cycles of CIE vapor or air exposure using a within-subjects design and a dose-response. Drug doses of 0, 40, 60, 80, and 100 mg/kg in saline were administered intraperitoneally (0.01 ml/g body weight) and in random order, with a 1-hour pretreatment time. Baseline 15E intake was re-established prior to administration of subsequent injections, with a maximum of 2 drug injections tested per week. RESULTS Tigecycline was found to effectively reduce high alcohol consumption in both dependent and nondependent female and male mice. CONCLUSIONS Our data suggest that tigecycline may be a promising drug with novel pharmacotherapeutic characteristics for the treatment of mild-to-severe AUD in both sexes.

The aim of the present study was to compare gene expression profiles in animals treated with abusable drugs. Wistar rats were treated with saline, morphine, chloral hydrate, or pentobarbital twice daily for 14 days. To induce neurotoxicity, a group of rats was treated with kainic acid. 24 hr after withdrawal, and a genome-wide DNA microarray analysis was conducted with the striata. A total of 57 gene expression patterns were altered in the three test groups; 35 of the 157 genes were selected when compared with the kainic acid treated group. Twenty-two of the 24 genes were functionally described in the gene library, and many were involved in long-term potentiation (LTP) and cell adhesion. The results were confirmed by quantitative reverse transcription-polymerase chain reaction analysis. Taken together, the selected genes may subserve identification of physical dependence biomarkers and contribute to determining the molecular mechanisms underlying physical dependence.

Background Previous studies show that some non-CB1/non-CB2 effects of cannabinoids are mediated through G protein coupled receptor 55 (GPR55). As this receptor is activated by some of cannabinoid receptor ligands and is involved in the modulation of pain, it was hypothesized that this receptor may also interact with opioids. This study examined the effect of atypical cannabinoid O-1602 as a GPR55 agonist on morphine-induced conditioned place preference (CPP) and physical dependence. Methods We used a biased CPP model to evaluate the effect of O-1602 (0.2, 1 and 5 mg/kg, intraperitoneal; ip ) on the acquisition and expression of morphine-induced CPP in male mice. The locomotor activities of mice were also recorded. Moreover, repeated administration of morphine (50, 50 and 75 mg/kg/day) for three days, induced physical dependence. The withdrawal signs such as jumps and diarrhea were precipitated by administration of naloxone (5 mg/kg, ip ). The effect of O-1602 on the development of morphine physical dependence was assessed by injection of O-1602 (0.2, 1 and 5 mg/kg) before morphine administrations. Results Morphine (40 mg/kg, subcutaneous; sc ), but not O-1602 (5 mg/kg) elicited significant preference in the post-conditioning phase. O-1602 at the doses of 0.2 and 1 mg/kg, but not 5 mg/kg reduced acquisition of morphine CPP with an increase in locomotor activity at the dose of 5 mg/kg. O-1602 at the doses of 0.2, 1 and 5 mg/kg also reduced expression of morphine CPP with an increase in locomotor activity at the dose of 5 mg/kg. O-1602 had a significant inhibitory effect on development of morphine-induced physical dependence at the dose of 5 mg/kg by decreasing jumps and diarrhea during withdrawal syndrome. Conclusions The present results indicate that O-1602 decreased acquisition and expression of morphine CPP and inhibited development of morphine-induced physical dependence.

The characteristics and functional roles of opioids originally present in vivo (endogenous opioids) in guinea-pig ileum were investigated. The release of endogenous opioids was determined by the inhibitory twitch response evoked by 0.1 Hz stimulation after 10 Hz stimulation (post-tetanic twitch inhibition). The effects of peptidase inhibitors increased the post-tetanic twitch inhibition, prevented by β-funaltrexamine and nor-binaltorphimine, which are selective μ- and κ-opioid receptor subtype antagonists, respectively. Dopamine receptor antagonists (haloperidol, sultopride and domperidone) increased the post-tetanic twitch inhibition. These results suggest that dopamine receptors are involved in modulation of the ileal opioid system, so as to diminish endogenous opioid release by tetanic stimulation, and dopamine antagonists increase the opioid action, that might depend more on the increased release of endogenous opioids. The post-tetanic twitch inhibition was inhibited by adrenalectomy, and showed the supersensitivity of the opioid receptors, resulting from a decrease of endogenous opioids by adrenalectomy. These findings suggest that the increase in morphine-analgesia by adrenalectomy was due to this process. In the presence of naloxone, an opioid antagonist, an increase in basal tension after tetanic stimulation (10 Hz stimulation) (post-tetanic contraction) was observed, and was blocked by spantide, a substance P antagonist, and indomethacin, a prostaglandins-biosynthesis inhibitor. This contraction increased with morphine or peptidase inhibitor exposure, depending on the length of time the ileum was exposed to the morphine or peptidase inhibitor. Post-tetanic contraction might be a useful indicator of the formation of physical dependence to morphine or endogenous opioids in the ileum.

Opioids are widely used drugs for treatment of pain and related disorders. Opiate addiction is a major public health concern in the United States causing significant increase in healthcare expenditure. They produce euphoria and sense of well-being which makes them addictive to some people. Used in higher doses they can lead to cardiac or respiratory compromise. They also impair cognition leading to impaired decision making. Opioids exert their effects by acting on three different types of receptors mu, delta, and kappa located on neuronal cell membranes causing inhibition of neurotransmitter release. Prolonged use of these drugs can lead to physical dependence causing withdrawal symptoms if a person stops using them. Commonly used medications to treat opiate addiction are methadone, LAAM (longer acting derivative of methadone), buprenorphine, and naltrexone.

Background Recent years have seen a rise in the diversity and use of synthetic cannabinoids. The present study evaluated the behavioral effects of the third-generation indazole-3-carboxamide-type synthetic cannabinoid, AB-FUBINACA. Methods Adult male and female C57BL/6J mice were treated with AB-FUBINACA (0−3 mg/kg, i.p.) and tested repeatedly in the tetrad battery measuring catalepsy, antinociception, hypothermia, and locomotor activity. Mice treated with AB-FUBINACA (≥2 mg/kg, i.p.) displayed classic cannabinoid effects in the tetrad that were blocked by the CB1 receptor selective antagonist rimonabant. To address tolerance and withdrawal effects, a second group of mice was injected with AB-FUBINACA (3 mg/kg, s.c.) or vehicle consisting of 5% ethanol, 5% Kolliphor EL, and 90 % saline every 12 h and tested daily in modified tetrad over the course of 5 days. On the 6th day, withdrawal was precipitated using rimonabant (3 mg/kg, s.c.), and somatic signs of withdrawal (i.e., head twitches and paw tremors) were quantified. Results Although mice did not develop tolerance to AB-FUBINACA or cross-tolerance to Δ9-tetrahydrocannabinol (THC; 50 mg/kg, i.p.), somatic precipitated withdrawal signs were observed. Repeated tetrad testing up to 48 h post injection indicated that AB-FUBINACA effects are relatively short-lived, as compared with THC. Brain levels of AB-FUBINACA, as quantified by UHPLC-MS/MS, were undetectable 4 h post injection. Conclusions These data indicate that the cannabinoid effects of AB-FUBINACA are relatively short-lived, yet sufficient to induce dependence in mice.

Opioid-induced neuroinflammation plays a role in the development of opioid physical dependence. Moreover, nitric oxide (NO) has been implicated in several oxidative and inflammatory pathologies. Here, we sought to determine whether treatment with venlafaxine during the development of morphine dependence could inhibit naloxone-precipitated withdrawal symptoms. The involvement of neuro-inflammation related cytokines, oxidative stress, and L-arginine (L-arg)-NO pathway in these effects were also investigated. Mice received morphine (50 mg/kg/daily; s.c.), plus venlafaxine (5 and 40 mg/kg, i.p.) once a day for 3 consecutive days. In order to evaluate the possible role of L-arg-NO on the effects caused by venlafaxine, animals received L-arg, L-NAME or aminoguanidine with venlafaxine (40 mg/kg, i.p.) 30 min before each morphine injection for 3 consecutive days. On 4th day of experiment, behavioral signs of morphine-induced physical dependence were evaluated after i.p. naloxone injection. Then, brain levels of tissue necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), brain-derived neurotrophic factor (BDNF), NO and oxidative stress factors including; total thiol, malondialdehyde (MDA) contents and glutathione peroxidase (GPx) activity were determined. Co-administration of venlafaxine (40 mg/kg) with morphine not only inhibited the naloxone-precipitated withdrawal signs including jumping and weight loss, but also reduced the up-regulation of TNF-α, IL-1β, IL-6, NO and MDA contents in mice brain tissue. However, repeated administration of venlafaxine inhibited the decrease in the brain levels of BDNF, total thiol and GPx. Pre-administration of L-NAME and aminoguanidine improved, while L-arg antagonized the venlafaxine-induced effects. These results provide evidences that venlafaxine could be used as a candidate drug to inhibit morphine withdrawal through the involvement of inflammatory cytokines and l-arginine-NO in mice.

Sumatriptan, a 5HT (5-hydroxytryptamine)1B/1D receptor agonist, showed neuroprotection in different studies. The aim of the present study was to investigate the effect of sumatriptan on morphine-induced antinociceptive tolerance and physical dependence. We also investigated the possible role of nitric oxide (NO) on sumatriptan effects. Tolerance was induced by morphine injection (50, 50, 75 mg/kg) three times daily for five days. Antinociceptive latency after acute and chronic treatment with sumatriptan (0.001, 0.01, 0.1 and 1 mg/kg) was measured by hot plate test in morphine-dependent animals. To investigate the possible involvement of NO, different isoforms of nitric oxide synthase (NOS) inhibitors including L-NAME, aminoguanidine and 7-nitroindazole were co-administered with sumatriptan. Nitrite level in mice hippocampus was quantified by Griess method. To examine the role of sumatriptan on physical dependence, three parameters of withdrawal signs were recorded after injection of naloxone (4 mg/kg). Acute treatment with sumatriptan (0.01, 0.1 and 1 mg/kg) attenuated the antinociceptive tolerance (P Acute and chronic administration of sumatriptan attenuated morphine antinociceptive tolerance; at least in chronic phase via nitrergic pathway. Our data did not support beneficial effects of sumatriptan on morphine-induced physical dependence in mice.

Opioid analgesics, such as morphine, oxycodone and fentanyl, are the cornerstones for treating moderate to severe pain. However, upon chronic administration, their efficiency is limited by prominent side effects such as analgesic tolerance and dependence liability. Neuropeptide FF (NPFF) and its receptors (NPFF1R and NPFF2R) are recognized as an important pronociceptive system involved in opioid-induced hyperalgesia and analgesic tolerance. Herein, we report the design of multitarget peptidomimetic compounds that show high affinity binding to the mu opioid receptor (MOPr) and NPFFRs. In vitro characterization of these compounds led to identification of KGFF03 and KGFF09 as G protein-biased MOPr agonists with full agonist or antagonist activity at NPFFRs, respectively. In agreement with their biased MOPr agonism, KGFF03/09 showed reduced respiratory depression in mice, as compared to the unbiased parent opioid agonist KGOP01. Chronic subcutaneous administration of KGOP01 and KGFF03 in mice rapidly induced hyperalgesia and analgesic tolerance, effects that were not observed upon chronic treatment with KGFF09. This favorable profile was further confirmed in a model of persistent inflammatory pain. In addition, we showed that KGFF09 induced less physical dependence compared to KGOP01 and KGFF03. Altogether, our data establish that combining, within a single molecule, the G protein-biased MOPr agonism and NPFFR antagonism, have beneficial effects on both acute and chronic side effects of conventional opioid analgesics. This strategy can lead to the development of novel and potent antinociceptive drugs with limited side effects upon acute and chronic administration.

Background Group 1 mGlu-family proteins (i.e., mGlu) consist of mGlu1 and mGlu5 and their activity may influence voluntary ethanol intake. The present studies sought to examine the influence of these receptors on the development of ethanol dependence using in vitro and in vivo models of chronic, intermittent ethanol (CIE). Methods Rat hippocampal explants were exposed to CIE with or without the addition of mGlu1 antagonist (7-hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt; 0.5, 1, and 3 μM) or mGlu5 antagonist (E)-2-methyl-6-styryl-pyridine (SIB-1893; 20, 100, and 200 μM) to assess sparing of withdrawal-induced cytotoxicity. In a separate study, adult male rats were administered CIE with or without the addition of oral administration of group 1 mGlu antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP; 3 mg/kg). Blood ethanol levels (BELs) were determined at 0930 h on Day 2 of Weeks 1, 2, and 3. Withdrawal behavior was monitored during Day 6 of the third consecutive withdrawal. Results CIE produced significant hippocampal cytotoxicity. These effects were attenuated by co-exposure to CPCCOEt (3 μM) with ethanol in the CA3. By contrast, these effects were blocked by SIB-1893 (20 μM) in each primary cell layer. Oral administration of MPEP with ethanol significantly attenuated behavioral effects of subsequent withdrawal and reduced BELs. Conclusions These data demonstrate that ethanol activates group 1 mGlu-family proteins to promote withdrawal-associated cytotoxicity in vitro and physical dependence in vivo. These findings suggest that group 1 mGlu-family proteins may be therapeutic targets for treatment of alcohol use disorders.

We report a novel approach to synthesize carfentanil amide analogues utilizing the isocyanide-based four-component Ugi multicomponent reaction. A small library of bis-amide analogues of carfentanil was created using N-alkylpiperidones, aniline, propionic acid, and various aliphatic isocyanides. Our lead compound showed high affinity for mu (MOR) and delta opioid receptors (DOR) with no appreciable affinity for kappa (KOR) receptors in radioligand binding assays. The compound was found to be a mixed MOR agonist/partial DOR agonist in [(35)S]GTPγS functional assays, and it showed moderate analgesic potency in vivo. The compound showed no visible signs of physical dependence or constipation in mice. In addition, it produced less respiratory depression than morphine. Most mixed MOR/DOR opioids reported in the literature are peptides and thereby systemically inactive. Our approach utilizing a multicomponent reaction has the promise to deliver potent and efficacious small-molecule analgesics with potential clinical utility.

Oxidative stress plays a role in the development of physical dependence induced by morphine. Bergenin, a polyphenol found in many Asian, African, and South American medicinal plants, is a potent antinarcotic agent with wide spectrum of pharmacological activities including antioxidant action. In the present study, we observed that bergenin decreased the development of physical dependence induced by morphine in mice and the antioxidant activity of bergenin plays a role in the antinarcotic effects through adapting to morphine-induced oxidative stress in the brain. The naloxone-precipitated withdrawal symptom (jumping frequency) was significantly ameliorated (50% of control group) by administration of bergenin (20 mg/kg) in morphine-treated mice. Furthermore, morphine-induced down-regulation of glutathione (GSH) contents was reversed by bergenin administration in the frontal cortex and liver. Bergenin had no effects on the increased levels of nfr2-dependent antioxidant enzyme HO1 and NQO1 in the frontal cortex, striatum, and liver of morphine-treated mice. However, the morphine-induced increase in nrf2 nuclear translocation in the frontal cortex and striatum was inhibited by bergenin treatment. These results suggest that bergenin has a potential antinarcotic effect via regulation of GSH contents and oxidative stress.

Despite acceptance that risk for alcohol-use disorder (AUD) has a large genetic component, the identification of genes underlying various components of risk for AUD has been hampered in humans, in part by the heterogeneity of expression of the phenotype. One aspect of AUD is physical dependence. Alcohol withdrawal is a serious consequence of alcohol dependence with multiple symptoms, many of which are seen in multiple species, and can be experienced over a wide-ranging time course. In the present three studies, we developed a battery of withdrawal tests in mice, examining behavioral symptoms from multiple domains that could be measured over time. To permit eventual use of the battery in different strains of mice, we used male and female mice of a genetically heterogeneous stock developed from intercrossing eight inbred strains. Withdrawal symptoms were assessed using commonly used tests after administration of ethanol in vapor for 72 continuous hours. We found significant effects of ethanol withdrawal versus air-breathing controls on nearly all symptoms, spanning 4 days following ethanol vapor inhalation. Withdrawal produced hypothermia, greater neurohyperexcitability (seizures and tremor), anxiety-like behaviors using an apparatus (such as reduced transitions between light and dark compartments), anhedonia (reduced sucrose preference), Straub tail, backward walking, and reductions in activity; however, there were no changes in thermal pain sensitivity, hyper-reactivity to handling, or anxiety-like emergence behaviors in other apparatus. Using these data, we constructed a refined battery of withdrawal tests. Individual differences in severity of withdrawal among different tests were weakly correlated at best. This battery should be useful for identifying genetic influences on particular withdrawal behaviors, which should reflect the influences of different constellations of genes.

Morphine dependence and the subsequent withdrawal syndrome restrict its clinical use in management of chronic pain. The precise mechanism for the development of dependence is still elusive. Thalidomide is a glutamic acid derivative, recently has been reconsidered for its clinical use due to elucidation of different clinical effects. Phosphoinositide 3-kinase (PI3K) is an intracellular transducer enzyme which activates Akt which in turns increases the level of nitric oxide. It is well established that elevated levels of nitric oxide has a pivotal role in the development of morphine dependence. In the present study, we aimed to explore the effect of thalidomide on the development of morphine dependence targeting PI3K/Akt (PKB) and nitric oxide (NO) pathways. Male NMRI mice and human glioblastoma T98G cell line were used to study the effect of thalidomide on morphine dependence. In both models the consequent effect of thalidomide on PI3K/Akt and/or NO signaling in morphine dependence was determined. Thalidomide alone or in combination with PI3K inhibitor, Akt inhibitor or nitric oxide synthase (NOS) inhibitors significantly reduced naloxone induced withdrawal signs in morphine dependent mice. Also, the levels of nitrite in hippocampus of morphine dependent mice were significantly reduced by thalidomide in compared to vehicle treated morphine dependent mice. In T98G human glioblastoma cells, thalidomide alone or in combination with PI3K and Akt inhibitors significantly reduced iNOS expression in comparison to the morphine treated cells. Also, morphine-induced p-Akt was suppressed when T98G cells were pretreated with thalidomide. Our results suggest that morphine induces Akt, which has a crucial role in the induction of NOS activity, leading to morphine dependence. Moreover, these data indicate that thalidomide attenuates the development of morphine dependence in vivo and in vitro by inhibition of PI3K/Akt and nitric oxide signaling pathways.

Caffeine is the most widely used psychotropic drug in the world. Most of the caffeine consumed comes from coffee bean (i.e., a misnomer for the seed of Coffee plants), beverages (i.e., coffee, tea, soft drinks), in products containing cocoa or chocolate and in medications (i.e., analgesics, stimulants, weight-loss products, sports nutrition). The most prominent behavioral effects of caffeine take place over low to moderate doses are amplified alertness and attention. Moderate caffeine consumption leads very rarely to health risks. Higher doses of caffeine encourage negative effects such as anxiety, insomnia, restlessness and tachycardia. The habitual use of caffeine causes physical dependence that displays as caffeine withdrawal symptoms that harm normal functioning. Contrariwise, rarely high doses of caffeine can encourage psychotic and manic symptoms usually, sleep disturbances and anxiety. Even though caffeine does not engender life-threatening health difficulties frequently related to the utilization of drugs of addiction, for example amphetamine, cocaine and heroin, an incrementing number of clinical studies are exhibiting that some caffeine users become dependent on the drug and are unable to reduce consumption despite knowledge of recurrent health complications linked to constant use. The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5), includes caffeine addiction and withdrawal as mental disorders. The World Health Organization (WHO) identifies caffeine dependence as a clinical disorder. Furthermore, diagnosis process of caffeine dependence syndrome is accepted by International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10). Therefore the intention of this study was to analyze the neuropsychological effects of caffeine and try to assess in which respect caffeine could be considered a potential drug of addiction.

Background The clinical benefits of opioid drugs are counteracted by the development of tolerance and addiction. We provide in vivo evidence for the involvement of G protein–coupled receptor kinases (GRKs) in opioid dependence in addition to their roles in agonist-selective mu-opioid receptor (MOR) phosphorylation. Methods In vivo MOR phosphorylation was examined by immunoprecipitation and nanoflow liquid chromatography–tandem mass spectrometry analysis. Using the hot-plate and conditioned place preference test, we investigated opioid-related antinociception and reward effects in mice lacking GRK3 or GRK5. Results Etonitazene and fentanyl stimulated the in vivo phosphorylation of multiple carboxyl-terminal phosphate acceptor sites, including threonine 370, serine 375, and threonine 379, which was predominantly mediated by GRK3. By contrast, morphine promoted a selective phosphorylation of serine 375 that was predominantly mediated by GRK5. In contrast to GRK3 knockout mice, GRK5 knockout mice exhibited reduced antinociceptive responses after morphine administration and developed morphine tolerance similar to wild-type mice but fewer signs of physical dependence. Also, morphine was ineffective in inducing conditioned place preference in GRK5 knockout mice, whereas cocaine conditioned place preference was retained. However, the reward properties of morphine were evident in knock-in mice expressing a phosphorylation-deficient S375A mutation of the MOR. Conclusions These findings show for the first time that MOR phosphorylation is regulated by agonist-selective recruitment of distinct GRK isoforms that influence different opioid-related behaviors. Modulation of GRK5 function could serve as a new approach for preventing addiction to opioids, while maintaining the analgesic properties of opioid drugs at an effective level.

The aim of this study was to evaluate the effects of orexin type-1 receptor (OX1R) antagonism in locus coeruleus (LC) nucleus on the development of morphine physical dependence in rats. Animals were rendered dependent on morphine by subcutaneous (s.c.) administration of morphine sulfate (6, 16, 26, 36, 46, 56 and 66 mg/kg, 2 ml/kg) at set intervals of 24 h for 7 days. Immediately before each morphine administration, the animals received intra-LC administration of SB-334867 (3 mM, 0.2 μl), a selective orexin type-1 receptor antagonist. On day 8, naloxone (3 mg/kg, i.p.) was injected and physical dependence was evaluated for 30 min. Our results showed that administration of OX1R antagonist before each morphine injection significantly decreased somatic signs of naloxone-induced morphine withdrawal syndrome, including defecation, wet-dog shake, diarrhea, jumping, scratching, and teeth chattering. These results suggest that the activation of OX1R in LC nucleus might be involved in the development of morphine dependency.

The use of alcohol is an important part of the daily lives of many individuals that may be experienced as a single nightly drink with a meal or a debilitating pattern of intoxication. The circadian timing system imposes a daily temporal order throughout the brain and body. Ethanol, with its complex and broad pharmacology, can thereby alter circadian physiology at multiple levels of organization. Here, we review data from animal models demonstrating that (a) perturbations of the circadian timing system are often, but not necessarily, reflected in altered drinking behaviors or ethanol response; (b) alcohol can act to alter the circadian entrainment and pacemaking functions of the suprachiasmatic nuclei; and (c) the temporal patterning of alcohol exposure and withdrawal in a circadian context can influence processes related to addiction development, particularly increased voluntary alcohol consumption and development of physical dependence as reflected in the physiological withdrawal reaction. New data are presented to show that the withdrawal reaction elicited after long-duration alcohol vapor sessions is significantly modulated according to the time of day that it is initiated. Further application of chronobiological principles to alcohol research should enhance mechanistic understanding and suggest potential therapeutic approaches.

We previously reported that nicotine (NIC)-induced analgesia was elicited in part by activation of the endogenous opioid system. Moreover, it is well known that NIC has physical-dependence liability, but its mechanism is unclear. Therefore, we examined whether physical dependence on NIC was mediated by activation of the endogenous opioid system in ICR mice. We evaluated increased serum corticosterone (SCS) as an indicator of NIC withdrawal, as it is a quantitative indicator of naloxone (opioid receptor antagonist, NLX)-precipitated morphine withdrawal in mice. In this study, NLX precipitated an SCS increase in mice receiving repeated NIC, by a dose-dependent mechanism, and correlated with the dose and number of days of repeated NIC administration. When an opioid receptor antagonist (naltrexone) was concomitantly administered with repeated NIC, the NLX-precipitated SCS increase was not elicited. Concomitant administration of the α7 nicotinic acetylcholine receptor (nAChR) antagonist (methyllycaconitine) with repeated NIC, but not the α4β2 nAChR antagonist (dihydro-β-erythroidine), did not elicit an SCS increase by NLX. Thus, a physical dependence on NIC was in part mediated by the activation of the endogenous opioid system, located downstream of α7 nAChR. Keywords:: nicotine, physical dependence, opioid system, corticosterone, α7 nicotinic acetylcholine receptor (nAChR)