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Background Binge alcohol drinking is considered a prominent risk factor for the development of alcohol-use disorders, and could be model in rodents through the standard two-bottle preference choice test. The goal was to recreate an intermittent use of alcohol during 3 consecutive days each week to ascertain its potential impact on hippocampal neurotoxicity (neurogenesis and other neuroplasticity markers), and including sex as a biological variable, given the well-known sex differences in alcohol consumption. Methods Ethanol access was granted to adult Sprague–Dawley rats for 3 consecutive days per week, followed by 4 days of withdrawal, during 6 weeks, mimicking the most common pattern of intake in people, drinking over the weekends in an intensive manner. Hippocampal samples were collected to evaluate signs of neurotoxicity. Results Female rats consumed significantly more ethanol than males, although intake did not escalate over time. Ethanol preference levels remained below 40% over time and did not differ between sexes. Moderate signs of ethanol neurotoxicity were observed in hippocampus at the level of decreased neuronal progenitors (NeuroD + cells), and these effects were independent of sex. No other signs of neurotoxicity were induced by ethanol voluntary consumption when measured through several key cell fate markers (i.e., FADD, Cyt c, Cdk5, NF-L) by western blot analysis. Conclusions Overall, the present results suggest that even though we modeled a situation where no escalation in ethanol intake occurred across time, mild signs of neurotoxicity emerged, suggesting that even the use of ethanol during adulthood in a recreational way could lead to certain brain harm.

Ketamine has been recently approved to treat resistant depression; however preclinical studies showed sex differences in its efficacy. Sex steroids, such as estrogen and testosterone, both in the periphery and locally in the brain, are regarded as important modulators of these sex differences. Therefore, the present study evaluated the role of inhibiting estrogen biosynthesis with letrozole, an aromatase inhibitor that catalyzes the conversion of androgen into estrogen, in the differential antidepressant-like-response induced by ketamine with sex. We performed several consecutive studies in adult Sprague-Dawley rats to evaluate potential sex differences in the antidepressant-like effects of ketamine (5 mg/kg, 7 days, i.p.), letrozole (1 mg/kg, 8 days, i.p.) and their combination (letrozole pre-treatment 3 h before ketamine). Acute and repeated antidepressant-like responses were ascertained in a series of behavioral tests (forced-swim, novelty-suppressed feeding, two-bottle choice for sucrose preference). The main results proved clear sex differences in the antidepressant-like response induced by ketamine, which was observed following a repeated paradigm in adult male rats, but rendered inefficacious in female rats. Moreover, decreasing estrogen production with letrozole induced on itself an antidepressant-like response in female rats, while also improved ketamine’s response in male rats (i.e., quicker response, only after a single dose). Interestingly, both the antidepressant-like effects induced by ketamine in male rats or letrozole in female rats persisted over time up to 65 days post-treatment, suggesting long-term sex-directed benefits for these drugs. The present results demonstrated a sex-specific role for inhibiting estrogen biosynthesis in the antidepressant-like response induced by ketamine in male rats. Moreover, letrozole presented itself as a potential antidepressant for females with persistent effects over time. Clearly, estrogen production is key in modulating, in a sex-specific manner, affective-like responses and thus deserve further studies.

In searching for novel targets to design antidepressants, among the characterized imidazoline receptors (IR), I2 receptors are an innovative therapeutical approach since they are dysregulated in major depressive disorder and by classical antidepressant treatments. In fact, several I2 agonists have been characterized for their antidepressant-like potential, but the results in terms of efficacy were mixed and exclusively reported in male rodents. Since there are well-known sex differences in antidepressant-like efficacy, this study characterized the potential effects induced by two I2 drugs, CR4056 (i.e., most promising drug already in phase II clinical trial for its analgesic properties) and B06 (a compound from a new family of bicyclic α-iminophosphonates) under the stress of the forced-swim test in male and female rats exposed to early-life stress. Moreover, some hippocampal neuroplasticity markers related to the potential effects observed were also evaluated (i.e., FADD, p-ERK/ERK, mBDNF, cell proliferation: Ki-67 + cells). The main results replicated the only prior study reporting the efficacy of CR4056 in male rats, while providing new data on its efficacy in females, which was clearly dependent on prior early-life stress exposure. Moreover, B06 showed no antidepressant-like effects in male or female rats. Finally, CR4056 increased FADD content and decreased cell proliferation in hippocampus, without affecting p-ERK/t-ERK ratio and/or mBDNF content. Interestingly, these effects were exclusively observed in female rats, and independently of early-life conditions, suggesting some distinctive molecular underpinnings participating in the therapeutic response of CR4056 for both sexes. In conjunction, these results present CR4056 with an antidepressant-like potential, especially in female rats exposed to stress early in life, together with some neuronal correlates described in the context of these behavioral changes in females., This research was partly supported by several grants to MJG-F: PID2020-118582RB-I00 (MCIN/AEI/10.13039/501100011033) and PDR2020/14 (Comunitat Autonoma ` de les Illes Balears through the Direccio ´ General de Política Universitaria ` i Recerca with funds from the Tourist Stay Tax Law ITS 2017–006). Moreover, this study was also funded by PID2019-107991RB-I00 (MCIN/AEI) and PDC2022-133441- I00 (MCIN/AEI/10.13039/501100011033 and by the “European Union NextGenerationEU/PRTR”) to CE. These entities had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. The salaries of personnel were covered by several research programs: predoctoral scholarships to EH-H (FPI/2102/2018) from Consejería de Innovacion, ´ Investigacion ´ y Turismo del Gobierno de las Islas Baleares y del Fondo Social Europeo, who is currently funded by the Margarita Salas Program (Ministerio de Universidades; Plan de Recuperacion, ´ Transformacion ´ y Resilencia; NextGenerationEU) with the participation of the University of the Balearic Islands; JUNIOR Program to SL-C from “TALENT PLUS Construint Salut, Generant Valor” (IdISBa, GOIB); CG is funded by the María Zambrano Program (Ministerio de Universidades; Plan de Recuperacion, ´ Transformacion ´ y Resilencia; NextGenerationEU) at the University of the Balearic Islands; AB received financial support from Institute of Biomedicine UB_2018.

Following methamphetamine consumption and during abstinence many behavioral consequences emerge (i.e., cognitive deficits, ongoing episodes of psychosis, depression, severe cravings, brain neurotoxicity), which are likely linked to propensity to relapse. In this line of thought, we recently showed that binge methamphetamine administration enhanced negative affect and voluntary drug consumption in rats, while it induced persistent neurotoxic effects (i.e., impaired hippocampal neurogenesis), effects that emerged long after drug removal. To date, no pharmacological strategies have been proven to be effective for the treatment of methamphetamine toxicity. A few studies have evaluated the impact of combining methamphetamine pretreatment with electroconvulsive seizures (ECS) post-treatment, an alternative non-pharmacological option used in psychiatry for resistant depression that offers a safe and really potent therapeutic response. Against this background, the present study aimed at testing whether repeated ECS treatment could ameliorate some of the long-term neurotoxicity effects induced by adolescent methamphetamine exposure in rats and emerging after drug removal. At the behavioral level, the main results showed that methamphetamine administration did not alter negative affect immediate during adolescence or later on in adulthood. Interestingly, repeated ECS improved the negative impact of methamphetamine administration on reducing hippocampal neurogenesis, demonstrating that ECS can attenuate certain degree of methamphetamine-induced neurotoxicity in rats, and suggesting ECS as a good therapeutical candidate that deserves further studies.

Rationale The combination of several risk factors (sex, a prior underlying psychiatric condition, or early drug initiation) could induce the emergence of negative affect during cocaine abstinence and increase the risk of developing addiction. However, most prior preclinical studies have been centered in male rodents, traditionally excluding females from these analyses. Objectives To ascertain the behavioral and neurochemical consequences of adolescent cocaine exposure when the combination of several risk factors is present (female, early-life stress). Methods Whole litters of Sprague–Dawley rats were exposed to maternal deprivation for 24 h on postnatal day (PND) 9. Cocaine was administered in adolescence (15 mg/kg/day, i.p., PND 33–39). Negative affect was assessed by several behavioral tests (forced swim, open field, novelty-suppressed feeding, sucrose preference). Hippocampal cell fate markers were evaluated by western blot (FADD, Bax, cytochrome c) or immunohistochemistry (Ki-67; cell proliferation). Results Maternal deprivation is a suitable model of psychiatric vulnerability in which to study the impact of adolescent cocaine in female rats. While adolescent cocaine did not alter affective-like behavior during adolescence, a pro-depressive–like state emerged during adulthood, exclusively in rats re-exposed to cocaine during abstinence. FADD regulation by cocaine in early-life stressed female rats might contribute to certain hippocampal neuroadaptations with some significance to the observed induced negative affect. Conclusions Adolescent cocaine induced persistent negative affect in female rats exposed to early-life stress, highlighting the risk of early drug initiation during adolescence for the emergence of negative reinforcement during abstinence likely driving cocaine addiction vulnerability, also in female rats.

Further studies are needed to better understand the effects of potential novel antidepressants, such as cannabidiol, for the treatment of psychiatric disorders during adolescence. In this context, we evaluated in a rodent model of early-life stress (a single 24-h episode of maternal deprivation, PND 9), the antidepressant-like effects of adolescent cannabidiol alone and/or in combination with adolescent cocaine exposure (given the described beneficial effects of cannabidiol on reducing cocaine effects). Maternally deprived Sprague-Dawley male rats were treated in adolescence with cannabidiol (with or without concomitant cocaine) and exposed to a battery of behavioral tests (forced-swim, novelty-suppressed feeding, open field, sucrose preference) across time. Putative enduring molecular correlates (CB receptors, BDNF) were evaluated in the hippocampus by western blot. Cannabidiol exerted antidepressant- and anxiolytic-like effects in rats exposed to early-life stress. Cocaine did not alter affective-like behavior during adolescence in rats exposed to early-life stress; however, a depressive- and anxiogenic-like phenotype emerged during adulthood, and cannabidiol exerted some behavioral improvements, along with the growing literature supporting its beneficial role for reducing cocaine intake and/or reinstatement in rodents. Finally, cannabidiol did not modulate hippocampal CB receptors or BDNF proteins, and although the data raised interesting questions about the possible role of CB1 receptors on modulating the long-term effects of cocaine, future research is needed to expand these findings. Cannabidiol showed a promising therapeutic response in terms of ameliorating affect in a rat model of early-life stress during adolescence and up to adulthood.

While early life drug use reliably predicts addiction liability in adulthood, the molecular mechanism by which this occurs, and the degree genetic predisposition is involved is not known. We used a unique genetic rat model of temperament to determine the impact of adolescent cocaine experience on adult psychomotor sensitization and epigenetic profiles in the striatum. Relative to adult bred low-responder (bLR) rats, bred high-responders (bHR) are more sensitive to the psychomotor-activating effects of cocaine and reinstate drug-seeking behavior more readily following prolonged cocaine exposure and a period of abstinence. We found that a 7-day sensitizing cocaine regimen (15 mg/kg/day) during either adolescence or adulthood produced psychomotor sensitization in bHRs only, while a dual cocaine exposure prevents further sensitization, suggesting limits on neuroplasticity. By contrast, adolescent cocaine in bLRs shifted their resilient phenotype, rendering them more responsive to cocaine in adulthood when initially challenged with cocaine We then assessed two functionally opposite epigenetic chromatin modifications, previously implicated in addiction liability, permissive acetylation (ac) and repressive tri-methylation (me3), on histone 3 lysine 9 (H3K9) in four sub-regions of the striatum. In bHRs, decreased repressive histone, H3K9me3, and increased permissive histone, acH3K9, in nucleus accumbens core associated with cocaine sensitization. However, there were limits on these epigenetic changes that paralleled the behavioral limits on further sensitization. In bLRs, the combination of cocaine exposure in adolescence and adulthood, which lead to an increase in their responsiveness to a cocaine challenge, also increased acH3K9 expression in the core. Thus, adolescent cocaine experience interacts with genetic background to elicit different behavioral profiles relevant to addiction in adulthood, with concurrent modifications in the epigenetic histone profiles in the nucleus accumbens that associate with cocaine sensitization and with metaplasticity.SIGNIFICANCE STATEMENTAdolescence is a critical period when brain developmental trajectories continue to be established and when most illicit drug use is initiated in humans. Notably, however, only a minority of adolescent drug users go on to develop substance use disorders in adulthood. We hypothesize that individual differences in genetic vulnerability, temperamental phenotype and adolescent drug history intersect to modify life-long drug abuse liability, with epigenetic modification playing an important role in this interplay. We tested this hypothesis in a genetic animal model of temperament. Our results show that adolescent cocaine experience induces psychomotor sensitization in vulnerable individuals, and that a dual exposure to cocaine (both in adolescence and adulthood) limits further sensitization in these individuals, an example of metaplasticity. By contrast, individuals who are typically resilient become more responsive to cocaine when exposed to this drug during adolescence and are then re-exposed as adults. Differences in behavioral response to cocaine were associated with unique epigenetic changes in the nucleus accumbens core. These findings shed light on the interplay of genes, environment and adolescent exposure to drugs in susceptibility to substance use disorders.

Age and sex are critical factors for the diagnosis and treatment of major depression, since there is a well-known age-by-sex difference in the prevalence of major depression (being females the most vulnerable ones) and in antidepressant efficacy (being adolescence a less responsive period than adulthood). Although the induction of electroconvulsive seizures (ECS) is a very old technique in humans, there is not much evidence reporting sexand age-specific aspects of this treatment. The present study evaluated the antidepressantand neurogenic-like potential of repeated ECS across time in adolescent and adult rats (naive or in a model of early life stress capable of mimicking a pro-depressive phenotype), while including a sex perspective. The main results demonstrated ageand sex-specific differences in the antidepressant-like potential of repeated ECS, since it worked when administered during adolescence or adulthood in male rats (although with a shorter length in adolescence), while in females rendered deleterious during adolescence and ineffective in adulthood. Yet, repeated ECS increased cell proliferation and vastly boosted young neuronal survival in a time-dependent manner for both sexes and independently of age. Moreover, pharmacological inhibition of basal cell proliferation prevented the antidepressant-like effect induced by repeated ECS in male rats, but only partially blocked the very robust increase in the initial cell markers of hippocampal neurogenesis. Overall, the present results suggest that the induction of the early phases of neurogenesis by ECS, besides having a role in mediating its antidepressant-like effect, might participate in some other neuroplastic actions, opening the path for future studies. (c) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/), Funding for this study was provided by Delegacion del Gobierno para el Plan Nacional sobre Drogas (grant 2016/002, MSSSI, Spain) and by Fundacion Alicia Koplowitz (Madrid, Spain) to MJG-F who is a member of RETICS-RTA (RD16/0017/0010; Instituto de Salud Carlos III, Ministerio de Ciencia e Innovacion FEDER); these entities had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. The program TECH from project TALENT PLUS Construint Salut, Generant Valor (IdISBa, GOIB) supported CB-H's salary. Open Access was funded by the program Liberi from IdISBa (GOIB).

Background The preclinical antidepressant-like characterization of desipramine relied almost exclusively in male rodents, with only a few contradictory reports done in females. Given that most experiments assessed a single dose and/or timepoint of analysis after-treatment, this study evaluated potential sex-differences in the length of the antidepressant-like response induced by different doses of desipramine as well as the molecular underpinnings driving the different responses by sex. Methods Male and female Sprague–Dawley rats were treated (i.p.) with 3 pulses of desipramine (5, 10 or 20 mg/kg) or vehicle (0.9% NaCl) within 24 h. The antidepressant-like effects were evaluated in the forced-swim test 1-h, 1- and 3-day post-treatment. The rate of cell proliferation and the regulation of key neuroplasticity markers (FADD, Cdk5, p35, p25) involved in antidepressant-like responses in the hippocampus were evaluated 1-h, 1-day and 5-day post-treatment. Results Desipramine induced similar antidepressant-like effects in male and female rats (effective doses of 10 and 20 mg/kg, with effects that lasted up to 1-day post-treatment), without altering the rate of cell proliferation. However, some sex-differences emerged when evaluating neuroplasticity markers in the hippocampus, while no changes were observed for female rats, desipramine regulated FADD, Cdk-5 and p25 in males in a way that suggested neuroprotective actions. Conclusions Our findings imply that while desipramine induced similar antidepressant-like responses for male and female rats, some differences emerged in the regulation of certain neuroplasticity markers, suggesting that distinctive molecular mechanisms might be participating in the therapeutic response of desipramine for both sexes.

Background Dysregulations of endocannabinoids and/or cannabinoid (CB) receptors have been implicated in the pathophysiology and treatment of major depressive disorder (MDD). Methods CB1 and CB2 receptors, neuroprotective mTOR (mechanistic target of rapamycin) and pro-apoptotic JNK1/2 (c-Jun-N-terminal kinases) were quantified by immunoblotting in postmortem prefrontal cortex of MDD and controls, and further compared in antidepressant (AD)-free and AD-treated subjects. Neuroplastic proteins (PSD-95, Arc, spinophilin) were quantified in MDD brains. Results Total cortical CB1 glycosylated (≈54/64 kDa) receptor was increased in MDD (+20%, n=23, p=0.02) when compared with controls (100%, n=19). This CB1 receptor upregulation was quantified in AD-treated (+23%, n=14, p=0.02) but not in AD-free (+14%, n=9, p=0.34) MDD subjects. In the same MDD cortical samples, CB2 glycosylated (≈45 kDa) receptor was unaltered (all MDD: +11%, n=23, p=0.10; AD-free: +12%, n=9, p=0.31; AD-treated: +10%, n=14, p=0.23). In MDD, mTOR activity (p-Ser2448 TOR/t-TOR) was increased (all MDD: +29%, n=18, p=0.002; AD-free: +33%, n=8, p=0.03; AD-treated: +25%, n=10, p=0.04). In contrast, JNK1/2 activity (p-Thr183/Tyr185/t-JNK) was unaltered in MDD subjects. Cortical PSD-95, Arc, and spinophilin contents were unchanged in MDD. Limitations A relative limited sample size. Some MDD subjects had been treated with a variety of ADs. The results must be understood in the context of suicide victims with MDD. Conclusions The upregulation of CB1 receptor density, but not that of CB2 receptor, as well as the increased mTOR activity in PFC/BA9 of subjects with MDD (AD-free/treated) support their contributions in the complex pathophysiology of MDD and in the molecular mechanisms of antidepressant drugs.

Besides early drug initiation during adolescence, another vulnerability factor associated with increased risk for substance abuse later in life is early-life stress. One way of assessing such combined risk is by evaluating the emergence of increased negative affect during withdrawal (i.e., linked to persistence in drug seeking). To compare the impact of maternal deprivation with cocaine exposure at different ages on affective-like behavior and hippocampal neuroplasticity regulation. Maternal deprivation was performed in whole-litters of Sprague-Dawley rats (24 h, PND 9-10). Cocaine (15 mg/kg, 7 days, i.p.) was administered in adolescence (PND 33–39) or adulthood (PND 64–70). Changes in affective-like behavior were assessed by diverse tests across time (forced-swim, open field, novelty-suppressed feeding, sucrose preference). Hippocampal multifunctional FADD protein (balance between cell death and plasticity) was evaluated by Western blot. Exposing rats to either maternal deprivation or adolescent cocaine did not modulate affective-like behavior immediately during adolescence, but increased negative affect in adulthood. Maternal deprivation combined with adolescent cocaine advanced the negative impact to adolescence. Adult cocaine exposure alone and/or in combination with maternal deprivation did not induce any behavioral changes at the time-points analyzed. FADD regulation might participate in the neural adaptations taking place in the hippocampus in relation to the observed behavioral changes. Adolescence is a more vulnerable period, as compared to adulthood, to the combined impact of cocaine and early maternal deprivation, thus suggesting that the accumulation of stress early in life can anticipate the negative behavioral outcome associated with drug consumption.

While the alteration of I2 receptors has been associated with neurodegenerative and psychiatric disorders, among other brain dysfunctions, I2 selective agonists are also capable of inducing analgesia in models of chronic pain, improving cognition and inducing hypothermia and neuroprotection. However, the literature evaluating the antidepressant-like potential of I2 ligands is scarce and showed mixed results, whereas some studies reported antidepressant-like effects for certain I2 ligands others denied them. In this context, we evaluated the antidepressant-like potential of a highly selective I2-receptor ligand, LSL 60101 ([2-(2-benzofuranyl)-2-imidazole]). LSL 60101 was administered in adult male Sprague–Dawley rats daily during 16 days (doses of 10 and 20 mg/kg, ip) and its antidepressant-like potential was assessed through the course of treatment in the forced-swim test, novelty-suppressed feeding test and two-bottle choice test (sucrose preference). The regulation of several key neuroplasticity markers (i.e., FADD, p-ERK1/2, ERK1/2, p-JNK1/2, JNK1/2, mBDNF) was evaluated 24-h post-treatment by western blot analysis in the right hippocampus and the proliferation of neural progenitors was quantified in the left hippocampus by immunohistochemistry. The results showed that LSL 60101 did not induce an antidepressant-like effect over the course of treatment in any of the behavioral tests conducted, and it did not alter any of the hippocampal neuroplasticity markers evaluated. These results add to the existing literature by suggesting that not all I2 ligands might be capable of displaying an antidepressant-like potential, and that particularities in the chemical structure of each compound might help explain these discrepancies and deserve future studies.

Cannabidiol is a non-psychoactive phytocannabinoid with great therapeutic potential in diverse psychiatric disorders; however, its antidepressant potential has been mainly ascertained in adult rats. To compare the antidepressant-like response induced by cannabidiol in adolescent and adult rats and the possible parallel modulation of hippocampal neurogenesis. Male Sprague-Dawley rats were repeatedly treated with cannabidiol (3, 10, and 30 mg/kg) or vehicle (1 mL/kg) during adolescence (postnatal days, PND 27-33) or adulthood (PND 141-147) and exposed to 3 consecutive tests (forced swim, open field, two-bottle choice) that quantified behavioral despair, anxiety, and sucrose intake respectively. Cannabidiol induced differential effects depending on the age and dose administered, with a decreased sensitivity observed in adolescent rats: (1) cannabidiol (30 mg/kg) decreased body weight only in adult rats; (2) cannabidiol ameliorated behavioral despair in adolescent and adult rats, but with a different dose sensitivity (10 vs. 30 mg/kg), and with a different extent (2 vs. 21 days post-treatment); (3) cannabidiol did not modulate anxiety-like behavior at any dose tested in adolescent or adult rats; and (4) cannabidiol increased sucrose intake in adult rats. Our findings support the notion that cannabidiol exerts antidepressant- and anorexigenic-like effects in adult rats and demonstrate a decreased potential when administered in adolescent rats. Moreover, since cannabidiol did not modulate hippocampal neurogenesis (cell proliferation and early neuronal survival) in adolescent or adult rats, the results revealed potential antidepressant-like effects induced by cannabidiol without the need of regulating hippocampal neurogenesis.

Antidepressant drugs elicit different behavioral and neurochemical responses with age. In fact, the use of antidepressants during adolescence is associated with an increased risk of suicidal thinking, being the best pharmacological treatment during this critical period a matter of constant debate in terms of its risk-benefit outcome. In this regard, the present study compared the effects of nortriptyline (3–10 mg/kg, 7 days) on regulating different aspects of affective-like behavior by screening adolescent and adult Sprague-Dawley rats through several consecutive tests (forced-swim, open field, sucrose preference). Brains were later collected to evaluate hippocampal neurogenesis and mBDNF protein content as potential molecular correlates of the observed behavioral responses. The main results in adolescent rats showed that nortriptyline induced dose-dependent opposite effects: while 3 mg/kg decreased immobility and increased mBDNF (indicative of an antidepressant-like response), 10 mg/kg decreased exploratory time in the open field and mBDNF (suggestive of an anxiogenic-like response). These effects were not associated with changes in neurogenesis regulation. In adult rats, nortriptyline failed to modulate affective-like behavior or the neuroplasticity markers evaluated at the doses tested. In conclusion, clear behavioral and neurochemical differences were observed between adolescent and adult rats in response to nortriptyline treatment. Interestingly, while nortriptyline displayed an antidepressant-like potential at the lowest dose examined in adolescence, a higher dose shifted these results towards a negative outcome, thus reinforcing the need to extreme caution when considering this treatment for our younger population.

Further studies are needed to better understand the effects of potential novel antidepressants, such as cannabidiol, for the treatment of psychiatric disorders during adolescence. In this context, we evaluated in a rodent model of early-life stress (a single 24-h episode of maternal deprivation, PND 9), the antidepressant-like effects of adolescent cannabidiol alone and/or in combination with adolescent cocaine exposure (given the described beneficial effects of cannabidiol on reducing cocaine effects).Maternally deprived Sprague-Dawley male rats were treated in adolescence with cannabidiol (with or without concomitant cocaine) and exposed to a battery of behavioral tests (forced-swim, novelty-suppressed feeding, open field, sucrose preference) across time. Putative enduring molecular correlates (CB receptors, BDNF) were evaluated in the hippocampus by western blot.Cannabidiol exerted antidepressant- and anxiolytic-like effects in rats exposed to early-life stress. Cocaine did not alter affective-like behavior during adolescence in rats exposed to early-life stress; however, a depressive- and anxiogenic-like phenotype emerged during adulthood, and cannabidiol exerted some behavioral improvements, along with the growing literature supporting its beneficial role for reducing cocaine intake and/or reinstatement in rodents. Finally, cannabidiol did not modulate hippocampal CB receptors or BDNF proteins, and although the data raised interesting questions about the possible role of CB1 receptors on modulating the long-term effects of cocaine, future research is needed to expand these findings.Cannabidiol showed a promising therapeutic response in terms of ameliorating affect in a rat model of early-life stress during adolescence and up to adulthood.

Recent findings unveil the pharmacological modulation of imidazoline I

Cognitive performance and affective-like responses are particularly susceptible to decline during the aging process. Since imidazoline receptors I

Imidazoline I

Imidazoline I2 receptors (I2-IR), widely distributed in the CNS and altered in patients that suffer from neurodegenerative disorders, are orphans from a structural point of view, and new I2-IR ligands are urgently required for improving their pharmacological characterization. We report the synthesis and three-dimensional quantitative structure−activity relationship (3D-QSAR) studies of a new family of bicyclic α-iminophosphonates endowed with relevant affinities for human brain I2-IR. Acute treatment in mice with a selected compound significantly decreased Fas-associated protein with death domain (FADD) in the hippocampus, a key signaling mediator of neuroprotective actions. Additionally, in vivo studies in the familial Alzheimer’s disease 5xFAD murine model revealed beneficial effects in behavior and cognition. These results are supported by changes in molecular pathways related to cognitive decline and Alzheimer’s disease. Therefore, bicyclic α-iminophosphonates are tools that may open new therapeutic avenues for I2-IR, particularly for unmet neurodegenerative conditions., We strongly acknowledge the advice of Dr Andrés G. Fernández (our mentor in the CaixaImpulse 2018 program) for unvaluable advice. This study was supported by the Ministerio de Economía y Competitividad of Spain (SAF2016-3307) and the Basque Government (IT1211- 19). The project leading to these results has received funding from “la Caixa” Foundation (ID 100010434) under agreement CI18-00002. This activity has received funding from the European Institute of Innovation and Technology (EIT). This body of the European Union receives support from the European Union’s Horizon 2020 research and innovation programme. C.G.-F, F. V., C. E., S. R-A., A. B. and M. P. belong to 2017SGR106 (Generalitat de Catalunya). J. A. G.-S. is a member emeritus of the Institut d’Estudis Catalans. Financial support was provided for F. V. (University of Barcelona, APIF_2017), S. R.-A. (Generalitat de Catalunya, 2018FI_B_00227), A. B. (Institute of Biomedicine UB_2018), C. M. (Marie Sklodowska-Curie Actions Individual Fellowships H2020-MSCA-IF-2016, ID747487), and E. H.-H. (Consejería de Innovación, Investigación y Turismo del Gobierno de las Islas Baleares y del Fondo Social Europeo, FPI/2102/2018). MR, TD and KN kindly acknowledge Ministry of Science and Technological Development of the Republic of Serbia, Project Contract No. 172033, and HORISON2020- COST-Action CA18133 ERNEST: European Research Network on Signal Transduction.

Background: The goal of the present study was to utilize the adolescent drug experience as an emerging vulnerability factor for developing psychiatric comorbidities in adulthood that could, in turn, help to elucidate and/or hypothesize possible mechanisms contributing to higher relapse rates. Outcomes: The current results showed that adolescent cocaine exposure (15 mg/kg, intraperitoneally, seven days) during early–mid adolescence (postnatal days 33–39) enhanced negative affect in adulthood, by increasing behavioral despair following drug re-exposure and by increasing anhedonia. Thus, these behavioral data provided a good model to further ascertain the long-term cellular and molecular adaptations that might take place in the brain in response to adolescent cocaine exposure as well as the impact of drug re-exposure in adulthood. In this regard, the results showed that adolescent cocaine exposure did not modulate cell proliferation (Ki-67+ cells) or c-Fos protein activation in the dentate gyrus region of the hippocampus, but attenuated c-Fos activation in the dorsal striatum. Conclusions: These results proved that a history of cocaine exposure during adolescence increased the vulnerability to induce negative affect (i.e. emergence of psychiatric comorbidity) in adulthood while it decreased neuronal activation in the dorsal striatum. Interestingly, these effects were only observed following cocaine re-exposure in adulthood, suggesting that avoiding drug contact in adulthood could prevent the long-term negative effects induced by adolescent cocaine.

A recent study from our laboratory demonstrated that binge methamphetamine induced hippocampal cell damage (i.e., impaired cell genesis) in rats when administered specifically during late adolescence (postnatal day, PND 54-57) and evaluated 24 h later (PND 58). The results also suggested a possible role for brain-derived neurotrophic factor (BDNF) regulating cell genesis and survival. This subsequent study evaluated whether these effects persisted in time as measured following prolonged withdrawal. Male Sprague-Dawley rats were treated (i.p.) with BrdU (2 × 50 mg/kg, 3 days, PND 48-50) followed by a binge paradigm (3 pulses/day, every 3 h, 4 days, PND 54-57) of methamphetamine (5 mg/kg, n = 14, M) or saline (0.9% NaCl, 1 ml/kg, n = 12, C). Following 34 days of forced withdrawal (PND 91), rats were killed 45 min after a challenge dose of saline (Sal: C-Sal, n = 6; M-Sal, n = 7) or methamphetamine (Meth: C-Meth, n = 6; M-Meth, n = 7). Neurogenesis markers (Ki-67: cell proliferation; NeuroD: early neuronal survival; BrdU: prolonged cell survival, 41–43 days old cells) were evaluated by immunohistochemistry while neuroplasticity markers (BDNF and Fos forms) were evaluated by Western blot. The main results showed that a history of methamphetamine administration (PND 54-57) induced enduring hippocampal cell damage (i.e., observed on PND 91) by decreasing cell survival (BrdU + cells) and mature-BDNF (m-BDNF) protein content, associated with neuronal survival, growth and differentiation. Interestingly, m-BDNF regulation paralleled hippocampal c-Fos protein content, indicating decreased neuronal activity, and thus reinforcing the persisting negative effects induced by methamphetamine in rat hippocampus following prolonged withdrawal.

While prior studies have established various interacting mechanisms and neural consequences (i.e. monoaminergic nerve terminal damage) that might contribute to the adverse effects caused by methamphetamine administration, the precise mechanisms that mediate relapse during withdrawal remain unknown. This study evaluated the long-term consequences of binge methamphetamine administration (three pulses/day, every 3 hours, 4 days, i.p.; dose-response: 2.5, 5 and 7.5 mg/kg) in adult Sprague-Dawley rats at two behavioral levels following 25 days of withdrawal: (1) negative affect (behavioral despair-forced-swim test, and anhedonia-1% sucrose consumption, two-bottle choice test) and (2) voluntary methamphetamine consumption (20 mg/l, two-bottle choice test). Striatal and hippocampal brain samples were dissected to quantify monoamines content by high-performance liquid chromatography and to evaluate neurotoxicity (dopaminergic and serotonergic markers) and neuroplasticity markers [i.e. cell fate regulator (Fas-associated protein with death domain) FADD] by Western blot. The results showed that methamphetamine administration induced dose-dependent negative effects during prolonged withdrawal in adult rats. In particular, rats treated repeatedly with methamphetamine (7.5 mg/kg) showed (1) enhanced negative affect-increased anhedonia associated with behavioral despair, (2) increased voluntary methamphetamine consumption, (3) enhanced neurotoxicity-decreased dopamine and metabolites in striatum and decreased serotonin in hippocampus, (4) altered neuroplasticity markers-decreased FADD protein and increased p-FADD/FADD balance selectively in hippocampus and (5) higher consumption rates of methamphetamine that were associated with lower FADD content in hippocampus. These results confirm that methamphetamine withdrawal dose-dependently induced negative affect and decreased monoamines content, while also increased voluntary methamphetamine consumption and suggested a role for hippocampal FADD neuroplasticity in these drug-withdrawal adaptations.

Environmental challenges during adolescence, such as drug exposure, can cause enduring behavioral and molecular changes that contribute to life-long maladaptive behaviors, including addiction. Selectively bred high-responder (bHR) and low-responder (bLR) rats represent a unique model for assessing the long-term impact of adolescent environmental manipulations, as they inherently differ on a number of addiction-related traits. bHR rats are considered “addiction-prone,” whereas bLR rats are “addiction-resilient,” at least under baseline conditions. Moreover, relative to bLRs, bHR rats are more likely to attribute incentive motivational value to reward cues, or to “sign-track.” We utilized bHR and bLR rats to determine whether adolescent cocaine exposure can alter their inborn behavioral and neurobiological profiles, with a specific focus on Pavlovian conditioned approach behavior (i.e., sign- vs. goal-tracking) and hippocampal neurogenesis. bHR and bLR rats were administered cocaine (15 mg/kg) or saline for 7 days during adolescence (postnatal day, PND 33–39) and subsequently tested for Pavlovian conditioned approach behavior in adulthood (PND 62–75), wherein an illuminated lever (conditioned stimulus) was followed by the response-independent delivery of a food pellet (unconditioned stimulus). Behaviors directed toward the lever and the food cup were recorded as sign- and goal-tracking, respectively. Hippocampal cell genesis was evaluated on PND 77 by immunohistochemistry. Adolescent cocaine exposure impaired hippocampal cell genesis (proliferation and survival) and enhanced the inherent propensity to goal-track in adult bLR, but not bHR, rats. Adolescent cocaine exposure elicits long-lasting changes in stimulus-reward learning and enduring deficits in hippocampal neurogenesis selectively in adult bLR rats.

Cannabidiol is a non-psychoactive phytocannabinoid with great therapeutic potential in diverse psychiatric disorders; however, its antidepressant potential has been mainly ascertained in adult rats.To compare the antidepressant-like response induced by cannabidiol in adolescent and adult rats and the possible parallel modulation of hippocampal neurogenesis.Male Sprague-Dawley rats were repeatedly treated with cannabidiol (3, 10, and 30 mg/kg) or vehicle (1 mL/kg) during adolescence (postnatal days, PND 27-33) or adulthood (PND 141-147) and exposed to 3 consecutive tests (forced swim, open field, two-bottle choice) that quantified behavioral despair, anxiety, and sucrose intake respectively.Cannabidiol induced differential effects depending on the age and dose administered, with a decreased sensitivity observed in adolescent rats: (1) cannabidiol (30 mg/kg) decreased body weight only in adult rats; (2) cannabidiol ameliorated behavioral despair in adolescent and adult rats, but with a different dose sensitivity (10 vs. 30 mg/kg), and with a different extent (2 vs. 21 days post-treatment); (3) cannabidiol did not modulate anxiety-like behavior at any dose tested in adolescent or adult rats; and (4) cannabidiol increased sucrose intake in adult rats.Our findings support the notion that cannabidiol exerts antidepressant- and anorexigenic-like effects in adult rats and demonstrate a decreased potential when administered in adolescent rats. Moreover, since cannabidiol did not modulate hippocampal neurogenesis (cell proliferation and early neuronal survival) in adolescent or adult rats, the results revealed potential antidepressant-like effects induced by cannabidiol without the need of regulating hippocampal neurogenesis.

The aim of this study was to compare the effects of amphetamine-like psychostimulant drugs (i.e., MDMA, methamphetamine, D-amphetamine) on rat hippocampal cell genesis at different developmental ages (i.e., early adolescence vs. young adulthood) to determine if there were periods of vulnerability to drug-induced brain changes. Although adolescence is a period of great vulnerability to the neurochemical effects of specific drugs of abuse, several reports suggest that adult rats are more susceptible than adolescents to the negative effects of these drugs. The main results suggest that the effects of these amphetamine drugs on cell genesis depend on the rat's developmental age, with the young adult period being more sensitive than the early adolescent one. In particular, MDMA and methamphetamine, but not D-amphetamine impaired hippocampal cell genesis (i.e., cell proliferation and cell survival) in young adult rats. These effects were dependent on the accumulative dose administered, as they were only observed with the highest dose tested (12 pulses of 5mg/kg over 4days: 60mg/kg total). The present results extend previous reports on adolescent insensitivity (i.e., better adaptation) to amphetamine-drugs and suggest for young adult rats certain degree of hippocampal damage that may mediate some of the addiction-like behaviors that depend on this brain region. Moreover, the present results, in line with previous data, suggest a possible role for the neuroplasticity marker BDNF and serotonin in regulating cell survival, as mBDNF protein regulation paralleled hippocampal cell survival and 5-HT2C-receptor content in young adult rats treated with these psychostimulant drugs.

This study evaluated the immediate and persistent behavioral and molecular consequences (i.e., emotional signs emerging during withdrawal and signs of neurotoxicity) following adolescent morphine exposure with a sex perspective. Basally, and prior to drug treatment, adolescent female rats showed smaller body weight and lower pain threshold than their male counterparts. Adolescent morphine treatment induced some sex-specific differences, while morphine impaired normal weight gain in male rats, no effects were observed for female rats. Plus, morphine produced an attenuated antinociceptive response in female rats. Moreover, following adolescent morphine treatment some emotional signs of withdrawal emerged exclusively in male rats in conjunction with signs of neurotoxicity, while female rats were not affected. In particular, an anxiolytic-like effect in adolescence during early withdrawal was followed by the development of a depressive-like phenotype (i.e., behavioral despair, anxiety-like behavior and anhedonia) in adulthood during prolonged withdrawal and paired with decreased contents of neurofilaments proteins in the prefrontal cortex. In conclusion, morphine administration during adolescence induced persistent changes in negative affect and brain toxicity selectively in male rats, suggesting female rats were resilient to these harmful effects. Given the widespread availability and use of opiate-based painkillers, the interplay between addiction, analgesia and emotional behaviors, and since adolescents and young adult humans are the age group with the highest abuse potential, these results add to the current literature by reporting distinct sex-specific opioid actions when administered in adolescence.

As populations increase their life expectancy, age-related neurodegenerative disorders such as Alzheimer’s disease have become more common. I(2)-Imidazoline receptors (I(2)-IR) are widely distributed in the central nervous system, and dysregulation of I(2)-IR in patients with neurodegenerative diseases has been reported, suggesting their implication in cognitive impairment. This evidence indicates that high-affinity selective I(2)-IR ligands potentially contribute to the delay of neurodegeneration. In vivo studies in the female senescence accelerated mouse-prone 8 mice have shown that treatment with I(2)-IR ligands, MCR5 and MCR9, produce beneficial effects in behavior and cognition. Changes in molecular pathways implicated in oxidative stress, inflammation, synaptic plasticity, and apoptotic cell death were also studied. Furthermore, treatments with these I(2)-IR ligands diminished the amyloid precursor protein processing pathway and increased Aβ degrading enzymes in the hippocampus of SAMP8 mice. These results collectively demonstrate the neuroprotective role of these new I(2)-IR ligands in a mouse model of brain aging through specific pathways and suggest their potential as therapeutic agents in brain disorders and age-related neurodegenerative diseases. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13311-018-00681-5) contains supplementary material, which is available to authorized users.

The aims of this study were (1) to behaviorally phenotype rats at different ages for both cognitive performance and affect, (2) to evaluate the possible beneficial effects of 8-OH-DPAT (a 5-HT1A receptor agonist) treatments on improving age-related behavioral deficits, and (3) to uncover putative key brain targets (e.g., Fas-associated protein with death domain [FADD] and related partners) that might contribute to the observed age-related behavioral changes. The principal results showed that acute, but not repeated, 8-OH-DPAT treatments improved age-related deficits in cognitive performance and affect while induced hypothermia. Moreover, multifunctional FADD protein decreased with age specifically in the hippocampus (as compared to the prefrontal cortex) and was further decreased following acute 8-OH-DPAT. The major conclusions indicate a parallelism between the beneficial effects observed following acute 8-OH-DPAT on improving the negative consequences of aging on cognition and affect, together with the acute induction of hypothermia and hippocampal FADD regulation. Because these effects were not observed following repeated treatment (i.e., observed tolerance to acute hypothermia), the results suggest 5-HT1A receptors desensitization and/or the activation of compensatory adaptive mechanisms.

The cell fate regulator Fas-associated death domain (FADD) balances cell death with non-apoptotic actions via its phosphorylated form. A recent study associated loss of cortical FADD with cognitive decline and increased risk of clinical dementia. Since the activation of cortical α2A-adrenoceptors improved memory deficits in various animal models of working memory loss, the present study evaluated whether UK-14304, an α2-adrenoceptor agonist known to acutely regulate brain FADD forms, would improve cognitive function in middle-aged rats. Sprague-Dawley rats were treated with UK-14304 (0.3 or 1 mg/kg) or saline (1 mL/kg) for seven days. Cognitive performance was evaluated in the eight-arm radial maze. FADD protein content was measured in the prefrontal cortex and hippocampus by Western blot analysis. The results showed that UK-14304 (1 mg/kg) improved cognitive performance (less time: -310±45 s, p=0.025 and fewer errors: -2.75±1.06, p=0.043 to complete the maze) and increased FADD selectively in the hippocampus (+35±11%, p=0.029). Interestingly, hippocampal FADD content negatively correlated with the time ( r=-0.651, p

While hippocampus is a brain region particularly susceptible to the effects of MDMA, the cellular and molecular changes induced by MDMA are still to be fully elucidated, being the dosage regimen, the species and the developmental stage under study great variables. This study compared the effects of one and four days of MDMA administration following a binge paradigm (3 × 5 mg/kg, i.p., every 2 h) on inducing hippocampal neurochemical changes in adolescent (PND 37) and young adult (PND 58) rats. The results showed that chronic MDMA caused hippocampal protein deficits in adolescent and young adult rats at different levels: (1) impaired serotonergic (5-HT 2A and 5-HT 2C post-synaptic receptors) and GABAergic (GAD2 enzyme) signaling, and (2) decreased structural cytoskeletal neurofilament proteins (NF-H, NF-M and NF-L). Interestingly, these effects were not accompanied by an increase in apoptotic markers. In fact, chronic MDMA inhibited proteins of the apoptotic pathway (i.e., pro-apoptotic FADD, Bax and cytochrome c) leading to an inhibition of cell death markers (i.e., p-JNK1/2, cleavage of PARP-1) and suggesting regulatory mechanisms in response to the neurochemical changes caused by the drug. The data, together with the observed lack of GFAP activation, support the view that chronic MDMA effects, regardless of the rat developmental age, extends beyond neurotransmitter systems to impair other hippocampal structural cell markers. Interestingly, inhibitory changes in proteins from the apoptotic pathway might be taking place to overcome the protein deficits caused by MDMA.

FADD is a crucial adaptor of death receptors that can engage apoptosis or survival actions (e.g. neuroplasticity) through its phosphorylated form (p-FADD). Although FADD was shown to participate in receptor mechanisms related to drugs of abuse, little is known on its role in the signaling of classic neurotransmitters (dopamine, noradrenaline, and serotonin) in brain. This study assessed the modulation of FADD (and p-FADD/FADD ratio, as an index of neuroplasticity) and FLIP-L (a neuroprotective FADD interacting partner), as well as the role of MEK-ERK signaling, after activation of monoamine auto/heteroreceptors by selective agonists in rat cortex. Acute depletion of monoamines with reserpine, but not with AMPT or PCPA, reduced FADD (28%) and increased p-FADD/FADD ratio (1.34-fold). Activation of presynaptic α2A-adrenoceptors (UK-14304 and clonidine), 5-HT1A receptors (8-OH-DPAT), and D2 dopamine receptor (bromocriptine) dose-dependently decreased FADD (up to 54%) and increased p-FADD (up to 29%) and p-FADD/FADD ratios (up to 2.93-fold), through specific receptor mechanisms. Activation of rat 5-HT1B autoreceptor in axon terminals by CP-94253 did not modulate FADD forms. Activation of postsynaptic D1 dopamine receptor by SKF-81297 also reduced FADD (25%) and increased p-FADD (32%). Disruption of MEK-ERK activation with SL327 did not modify clonidine (α2A-adrenoceptor)-induced FADD inhibition, indicating that agonist effect was not dependent on ERK signaling. The various monoamine receptor agonists and antagonists did not alter FLIP-L content, or the activation of executioner caspase-3 and PARP-1 cleavage, indicating that the agonists attenuated apoptotic signals and promoted neuroplasticity through FADD regulation. These novel results indicate that inhibition of pro-apoptotic FADD adaptor could function as a common signaling step in the initial activation of monoamine receptors in the brain.

While prior studies have established various interacting mechanisms and neural consequences (i.e. monoaminergic nerve terminal damage) that might contribute to the adverse effects caused by methamphetamine administration, the precise mechanisms that mediate relapse during withdrawal remain unknown. This study evaluated the long-term consequences of binge methamphetamine administration (three pulses/day, every 3 hours, 4 days, i.p.; dose-response: 2.5, 5 and 7.5 mg/kg) in adult Sprague-Dawley rats at two behavioral levels following 25 days of withdrawal: (1) negative affect (behavioral despair-forced-swim test, and anhedonia-1% sucrose consumption, two-bottle choice test) and (2) voluntary methamphetamine consumption (20 mg/l, two-bottle choice test). Striatal and hippocampal brain samples were dissected to quantify monoamines content by high-performance liquid chromatography and to evaluate neurotoxicity (dopaminergic and serotonergic markers) and neuroplasticity markers [i.e. cell fate regulator (Fas-associated protein with death domain) FADD] by Western blot. The results showed that methamphetamine administration induced dose-dependent negative effects during prolonged withdrawal in adult rats. In particular, rats treated repeatedly with methamphetamine (7.5 mg/kg) showed (1) enhanced negative affect-increased anhedonia associated with behavioral despair, (2) increased voluntary methamphetamine consumption, (3) enhanced neurotoxicity-decreased dopamine and metabolites in striatum and decreased serotonin in hippocampus, (4) altered neuroplasticity markers-decreased FADD protein and increased p-FADD/FADD balance selectively in hippocampus and (5) higher consumption rates of methamphetamine that were associated with lower FADD content in hippocampus. These results confirm that methamphetamine withdrawal dose-dependently induced negative affect and decreased monoamines content, while also increased voluntary methamphetamine consumption and suggested a role for hippocampal FADD neuroplasticity in these drug-withdrawal adaptations.

Background: FADD (Fas-associated death domain) adaptor is a crucial protein involved in the induction of cell death but also mediates non-apoptotic actions via a phosphorylated form (p-Ser194-FADD). This study investigated the possible association of FADD forms with age-related neuropathologies, cognitive function, and the odds of dementia in an elderly community sample. Methods: FADD forms were quantified by western blot analysis in dorsolateral prefrontal cortex (DLPFC) samples from a large cohort of participants in a community-based aging study (Memory and Aging Project, MAP), experiencing no-(NCI, n = 51) or mild-(MCI, n = 42) cognitive impairment, or dementia (n = 57). Results: Cortical FADD was lower in subjects with dementia and lower FADD was associated with a greater load of amyloid-beta pathology, fewer presynaptic terminal markers, poorer cognitive function and increased odds of dementia. Together with the observations of FADD redistribution into tangles and dystrophic neurites within plaques in Alzheimer's disease brains, and its reduction in APP23 mouse cortex, the results suggest this multifunctional protein might participate in the mechanisms linking amyloid and tau pathologies during the course of the illness. Conclusions: The present data suggests FADD as a putative biomarker for pathological processes associated with the course of clinical dementia., This study was supported by SAF2014-55903-R to MJG-F from Ministerio de Economia y Competitividad (MINECO, Spain), and by Grants MT-14037 and MOP-81112 to WGH from the Canadian Institutes of Health Research. The Memory and Aging Project is a collaborative, multidisciplinary and translational research project subsidized by the National Institute on Aging (Grants R01AG42210).

Fas-associated death domain (FADD) is an adaptor of death receptors that can also induce anti-apoptotic actions through its phosphorylated form (p-FADD). Activation of monoamine receptors, indirect targets of classic anti-depressant drugs (ADs), reduced FADD and increased p-FADD and p-FADD/FADD ratio in brain. To ascertain whether ADs, which indirectly regulate monoamine receptors, modulate FADD protein forms to promote anti-apoptotic actions. The effects of selected norepinephrine transporter (NET), serotonin transporter (SERT), monoamine oxidase (MAO) inhibitors, atypical ADs, and electroconvulsive shock (ECS) or behavioral procedures (forced swim test, FST) on FADD forms and pro-survival FADD-like interleukin-1β-converting enzyme-inhibitory protein (FLIP-L) and phosphoprotein enriched in astrocytes of 15 kDa (p-PEA-15) contents were assessed in rat brain cortex by western blot analysis. Acute NET (e.g., nisoxetine) but not SERT (e.g., fluoxetine) inhibitors decreased cortical FADD (up to 37 %) and increased p-FADD/FADD ratio (up to 1.9-fold). Nisoxetine effects were prevented by α2-antagonist RX-821002, suggesting the involvement of presynaptic α2-autoreceptors. Immobility time in the FST correlated with increases of pro-apoptotic FADD and decreases of anti-apoptotic p-FADD. The MAO-A/B inhibitor phenelzine decreased FADD (up to 33 %) and increased p-FADD (up to 65 %) and p-FADD/FADD (up to 2.4-fold). Other MAO inhibitors (clorgyline, Ro 41-1049, rasagiline), atypical ADs (ketamine and mirtazapine), or ECS did not modulate cortical FADD. Chronic (14 days) desipramine and fluoxetine, but not phenelzine, increased p-FADD (up to 59 %), p-FADD/FADD ratio (up to 1.8-fold), and pro-survival p-PEA-15 (up to 46 %) in rat brain cortex. Multifunctional FADD protein, through an increased p-FADD/FADD ratio, could participate in the mechanisms of anti-apoptotic actions induced by ADs.

This chapter summarizes the current data studying the effects of cocaine on altering the balance between the induction of aberrant apoptotic cell death (i.e., neurotoxicity) and nonapoptotic events (i.e., neuroplasticity) mediated through the activation of Fas receptor and Fas-associated protein (FADD) in the rat brain and the human postmortem brain. The findings presented here reveal important differences between humans and rats concerning the long-term regulation of the extrinsic apoptotic pathway by cocaine in the brain. The Fas/FADD complex is downregulated in the prefrontal cortex of human cocaine addicts, while it shows tolerance to an acute upregulation in the brain of cocaine-treated rats. The modulation of Fas receptor and more interestingly that of FADD adaptor by cocaine is a new and relevant molecular process in the complex neurobiology of cocaine addiction, suggesting long-term contraregulatory adaptations or nonapoptotic actions.

Opiate addiction is characterized by drug tolerance and dependence which involve adaptive changes in μ-opioid receptors (MORs) signaling. Regulators of G-protein signaling RGS9, RGS4 and RGS10 proteins negatively regulate Gαi/o protein activity modulating MOR function. An important role of RGS proteins in drug addiction has been described but the status of RGS proteins in human brain of opiate addicts remains unknown. The present study evaluated the immunoreactivity levels of RGS4, RGS9 and RGS10 proteins in prefrontal cortex of short- (n = 15) and long-term (n = 21) opiate abusers and in matched control subjects. RGS4 protein was not altered in short-term opiate abusers but, in long-term abusers it was significantly up-regulated (Δ = 29 ± 6%). RGS10 protein expression was significantly decreased in short-term (Δ = −42 ± 7%) but remained unaltered in long-term opiate abusers. RGS9 protein levels in opiate abusers did not differ from matched controls either in the short-term or in the long-term opiate abuser groups. RGS4, RGS9 and RGS10 levels were also studied in brains (frontal cortex) of rats submitted to acute and chronic morphine treatment and to spontaneous and naloxone-precipitated opiate withdrawal. Chronic morphine treatment in rats was associated with an increase in RGS4 protein immunoreactivity (Δ = 28 ± 7%), which persisted in spontaneous (Δ = 35 ± 8%) and naloxone-precipitated withdrawal (Δ = 30 ± 9%) without significant changes in RGS9 and RGS10 proteins. The specific modulation of RGS4 and RGS10 protein expression observed in the prefrontal cortex of opiate abusers might be relevant in the neurobiology of opiate tolerance, dependence and withdrawal. This article is part of a Special Issue entitled ‘Post-Traumatic Stress Disorder’.