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Background and Purpose: Neuroactive steroid (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile (3β-OH) is a novel hypnotic and voltage-dependent blocker of T-type calcium channels. Here, we examine its potential analgesic effects and adjuvant anaesthetic properties using a post-surgical pain model in rodents. Experimental Approach: Analgesic properties of 3β-OH were investigated in thermal and mechanical nociceptive tests in sham or surgically incised rats and mice, with drug injected either systemically (intraperitoneal) or locally via intrathecal or intraplantar routes. Hypnotic properties of 3β-OH and its use as an adjuvant anaesthetic in combination with isoflurane were investigated using behavioural experiments and in vivo EEG recordings in adolescent rats. Key Results: A combination of 1% isoflurane with 3β-OH (60 mg·kg−1, i.p.) induced suppression of cortical EEG and stronger thermal and mechanical anti-hyperalgesia during 3 days post-surgery, when compared to isoflurane alone and isoflurane with morphine. 3β-OH exerted prominent enantioselective thermal and mechanical antinociception in healthy rats and reduced T-channel-dependent excitability of primary sensory neurons. Intrathecal injection of 3β-OH alleviated mechanical hyperalgesia, while repeated intraplantar application alleviated both thermal and mechanical hyperalgesia in the rats after incision. Using mouse genetics, we found that CaV3.2 T-calcium channels are important for anti-hyperalgesic effect of 3β-OH and are contributing to its hypnotic effect. Conclusion and Implications: Our study identifies 3β-OH as a novel analgesic for surgical procedures. 3β-OH can be used to reduce T-channel-dependent excitability of peripheral sensory neurons as an adjuvant for induction and maintenance of general anaesthesia while improving analgesia and lowering the amount of volatile anaesthetic needed for surgery.

Despite significant advances in understanding the role of benzodiazepine (BZ)-sensitive populations of GABA A receptors, containing the α 1 , α 2 , α 3 or α 5 subunit, factual substrates of BZ-induced learning and memory deficits are not yet fully elucidated. It was shown that α 1 -subunit affinity-selective antagonist Β-CCt almost completely abolished spatial learning deficits induced by diazepam (DZP) in the Morris water maze. We examined a novel, highly (105 fold) α 1 -subunit selective ligand-WYS8 (0.2, 1 and 10mg/kg), on its own and in combination with the non-selective agonist DZP (2mg/kg) or Β-CCt (5mg/kg) in the water maze in rats. The in vitro efficacy study revealed that WYS8 acts as α 1 -subtype selective weak partial positive modulator (40% potentiation at 100nM). Measurement of concentrations of WYS8 and DZP in rat serum and brain tissues suggested that they did not substantially cross-influence the respective disposition. In the water maze, DZP impaired spatial learning (acquisition trials) and memory (probe trial). WYS8 caused no effect per se, did not affect the overall influence of DZP on the water-maze performance and was devoid of any activity in this task when combined with Β-CCt. Nonetheless, an additional analysis of the latency to reach the platform and the total distance swam suggested that WYS8 addition attenuated the run-down of the spatial impairment induced by DZP at the end of acquisition trials. These results demonstrate a clear difference in the influence of an α 1 subtype-selective antagonist and a partial agonist on the effects of DZP on the water-maze acquisition.

Synthesis of ligands inactive or with low activity at alpha(1) GABA(A) receptors has become the key concept for development of novel, more tolerable benzodiazepine (BZ)-like drugs. WYS8, a remarkably (105 times) alpha(1)-subtype selective partial positive modulator, may serve as a pharmacological tool for refining the role of alpha(1) GABA(A) receptors in mediation of BZs' effects. Here, the effects of WYS8 on GABA-induced currents and on diazepam-induced potentiation of recombinant BZ-sensitive GABA(A) receptors were studied in more detail. In addition, the behavioral profile of WYS8 (0.2, 1, and 10 mg/kg i.p.), on its own and in combination with diazepam, was tested in the spontaneous locomotor activity, elevated plus maze, grip strength, rotarod, and pentylenetetrazole tests. WYS8, applied at an in vivo attainable concentration of 100 nM, reduced the stimulation of GABA currents by 1 mu M diazepam by 57 % at alpha(1)beta(3)gamma(2), but not at alpha(2)beta(3)gamma(2), alpha(3)beta(3)gamma(2), or alpha(5)beta(3)gamma(2) GABA(A) receptors. The administration of WYS8 alone induced negligible behavioral consequences. When combined with diazepam, WYS8 caused a reduction in sedation, muscle relaxation, and anticonvulsant activity, as compared with this BZ alone, whereas ataxia was preserved, and the anxiolytic effect of 2 mg/kg diazepam was unmasked. Hence, a partial instead of full activation at alpha(1) GABA(A) receptors did not necessarily result in the attenuation of the effects assumed to be mediated by activation of these receptors, or in the full preservation of the effects mediated by activation of other GABA(A) receptors. Thus, the role of alpha(1) GABA(A) receptors appears more complex than that proposed by genetic studies.

Reportedly, negative modulation of alpha(5) GABA(A) receptors may improve cognition in normal and pharmacologically-impaired animals, and such modulation has been proposed as an avenue for treatment of cognitive symptoms in schizophrenia. This study assessed the actions of PWZ-029, administered at doses (2, 5, and 10 mg/kg) at which it reached micromolar concentrations in brain tissue with estimated free concentrations adequate for selective modulation of alpha(5) GABA(A) receptors, in three cognitive tasks in male Wistar rats acutely treated with the noncompetitive N-methyl-D-aspartate receptor antagonist, MK-801 (0.1 mg/kg), as well in tests of locomotor activity potentiated by MK-801 (0.2 mg/kg) or amphetamine (0.5 mg/kg). In a hormetic-like manner, only 5 mg/kg PWZ-029 reversed MK-801-induced deficits in novel object recognition test (visual recognition memory), whereas in the Morris water maze, the 2 mg/kg dose of PWZ-029 exerted partial beneficial effects on spatial learning impairment. PWZ-029 did not affect recognition memory deficits in social novelty discrimination procedure. Motor hyperactivity induced with MK-801 or amphetamine was not preventable by PWZ-029. Our results show that certain MK-801-induced memory deficits can be ameliorated by negative modulation of alpha(5) GABA(A) receptors, and point to the need for further elucidation of their translational relevance to cognitive deterioration in schizophrenia.

Kompleksna klinička slika neuropatije nakon povrede perifernog nerva često je praćena i promenama afektivnog stanja pacijenata. U animalnim modelima bola pokazano je da pozitivni alosterni modulatori GABAA receptora mogu da smanje nociceptivnu transmisiju. Međutim, skorašnji nalazi ukazuju i na mogućnost da je prividni Obradović et al. 199 antinociceptivni efekat benzodiazepina nakon delovanja akutnog bolnog stimulusa u značajnoj meri posledica anksiolitičnog efekta. U ovoj studiji ispitani su mogući odloženi efekti novosintetisanog, neselektivnog liganda GABAA receptora (SH–I–048A) na lokomotornu aktivnost i ponašanje u vezi sa anksioznošću kod pacova soja Wistar prethodno podvrgnutih povredi perifernog nerva. Procena bihejvioralnih parametara sprovedena je testovima spontane lokomotorne aktivnosti i uzdignutog plus lavirinta 48 sati nakon što su životinje u periodu od 24 sata primile rastvarač, jednu, dve ili tri doze SH–I–048A (10 mg/kg). Generalno, ponašanje pacova praćeno 72 sata nakon umerene povrede perifernog nerva nije ukazivalo na prisustvo perzistentnih posledica neuropatskog bola. Pacovi prethodno tretirani sa tri doze SH–I–048A ispoljili su povećano vreme imobilnosti u testu lokomotorne aktivnosti, bez značajnog smanjenja ukupnog pređenog puta. S druge strane, u grupi koja je tretirana sa dve doze SH–I–048A zapažena je smanjena emocionalna reaktivnost u uzdignutom plus lavirintu. Kod životinja sa povredom perifernog nerva, suptilne razlike u režimu doziranja pozitivnog modulatora GABAA, mogu značajno da utiču na ponašanje vezano za lomotornu aktivnost i nivo anksioznosti.

In this work there was investigated the influence of selenium and deodinases blockers on juvenile rats body weight during three months. The experiment was carried out on 64 rats divided into eight groups with eight individual animals per group. Following groups were formed: 1. Se+PTU-IA- (control group), 2. Se+PTU+IA+, 3. Se+PTU+IA-, 4. Se+P-TU-IA+, 5. Se-PTU-IA-, 6. Se-PTU+IA+, 7. Se-PTU+IA- and 8. Se-PTU-IA+. The groups labeled (Se+) were selenium adequate and they were fed with food that contained 0.334 mg Se/kg. The groups labeled (Se-) were selenium deficient and obtained food with 0.031 mg Se/kg. As deiodinases blockers there were used propylthiouracil (PTU+) in a dose of 150 mg/L of drinking water and iopanoic acid (IA+) in a dose of 6 mg/100 g TM intraperitoneally. Body weight of experimental rats was measured every seven days. After three weeks of treatment there were taken blood samples of animals from all experimental groups and following parameters were determined: selenium concentration in blood, thyroxine (T4), triiodothyronine (T3) and thyroidstimulating hormone (TSH) in blood plasma. Analysis of the samples showed that the animals from the groups treated with PTU had lower body weight in regard to the control group, as well as lower concentration of T3 and T4 in plasma. Selenium deficient rats had lower average body weight compared to the selenium adequate ones after three weeks, but there were no differences in thyroid hormones concentration. The lowest average body weight was noticed in selenium deficient rats groups treated with PTU., U okviru ogleda je ispitivan uticaj selena i blokatora dejodinaza na telesnu masu juvenilnih pacova tokom tri nedelje. Ogled je izveden na 64 pacova podeljenih u osam grupa od po 8 jedinki. Formirane su sledeće grupe: 1. Se+PTU-IA- (kontrolna grupa), 2. Se+PTU+IA+, 3. Se+PTU+IA-, 4. Se+PTU-IA+, 5. Se-PTU-IA-, 6. Se-PTU+IA+, 7. Se-PTU+IA- i 8. Se-PTU-IA+. Grupe sa oznakom (Se+) su bile selenadekvatne i dobijale su hranu koja je sadržala 0,334 mg Se/kg hrane. Grupe sa oznakom (Se-) su bile selendeficitne i dobijale su 0,031 mg mg Se/kg hrane. Kao blokatori dejodinaza su korišćeni propiltiouracil (PTU+) u dozi od 150 mg/L vode za piće i jopanoična kiselina (IA+) u dozi od 6 mg/100g t.m. intraperitonealno. Telesna masa oglednih pacova je merena svakih sedam dana. Nakon tri nedelje tretmana uzeti su uzorci krvi životinja iz svih oglednih grupa i određivani su sledeći parametri: koncentracja selena u punoj krvi, tiroksin (T4), trijodtironin (T3) i tireostimulirajući hormon (TSH) u krvnoj plazmi. Analiza je pokazala da su jedinke iz grupe tretiranih sa PTU imale nižu telesnu masu u odnosu na kontrolnu, kao i nižu koncentraciju T3 i T4 u plazmi. Selendeficitni pacovi su nakon tri nedelje imali nižu prosečnu telesnu masu u odnosu na selenadekvatne, ali nisu uočene razlike u koncentraciji tireoidnih hormona. Najniža prosečna telesna masa zabeležena je kod selendeficitnih grupa pacova tretiranih sa PTU.

Long-term use of benzodiazepine-type drugs may lead to physical dependence, manifested by withdrawal syndrome after abrupt cessation of treatment. The aim of the present study was to investigate the influence of duration of treatment, as well as the role of alpha(1)-containing GABA(A) receptors, in development of physical dependence to diazepam, assessed through the level of anxiety and susceptibility to pentylenetetrazole (PTZ)-induced seizures, 24 h after withdrawal from protracted treatment in rats. Withdrawal of 2 mg/kg diazepam after 28, but not after 14 or 21 days of administration led to an anxiety-like behavior in the elevated plus maze. Antagonism of the diazepam effects at alpha(1)-containing GABA(A) receptors, achieved by daily administration of the neutral modulator beta CCt (5 mg/kg), did not affect the anxiety level during withdrawal. An increased susceptibility to PTZ-induced seizures was observed during diazepam withdrawal after 21 and 28 days of treatment. Daily co-administration of beta CCt further decreased the PTZ-seizure threshold after 21 days of treatment, whilst it prevented the diazepam withdrawal-elicited decrease of the PTZ threshold after 28 days of treatment. In conclusion, the current study suggests that the role of alpha(1)-containing GABA(A) receptors in mediating the development of physical dependence may vary based on the effect being studied and duration of protracted treatment. Moreover, the present data supports previous findings that the lack of activity at alpha(1)-containing GABA(A) receptors is not sufficient to eliminate physical dependence liability of ligands of the benzodiazepine type.

Enormous progress in understanding the role of four populations of benzodiazepine-sensitive GABA(A) receptors was paralleled by the puzzling findings suggesting that substantial separation of behavioral effects may be accomplished by apparently nonselective modulators. We report on SH-I-048A, a newly synthesized chiral positive modulator of GABAA receptors characterized by exceptional subnanomolar affinity, high efficacy and non-selectivity. Its influence on behavior was assessed in Wistar rats and contrasted to that obtained with 2 mg/kg diazepam. SH-I-048A reached micromolar concentrations in brain tissue, while the unbound fraction in brain homogenate was around 1.5%. The approximated electrophysiological responses, which estimated free concentrations of SH-I-048A or diazepam are able to elicit, suggested a similarity between the 10 mg/kg dose of the novel ligand and 2 mg/kg diazepam; however, SH-I-048A was relatively more active at and as-containing GABAA receptors. Behaviorally, SH-I-048A induced sedative, muscle relaxant and ataxic effects, reversed mechanical hyperalgesia 24 h after injury, while it was devoid of clear anxiolytic actions and did not affect water-maze performance. While lack of clear anxiolytic actions may be connected with an enhanced potentiation at al-containing GABAA receptors, the observed behavior in the rotarod, water maze and peripheral nerve injury tests was possibly affected by its prominent action at receptors containing the as subunit. The current results encourage further innovative approaches aimed at linking in vitro an in vivo data in order to help define fine-tuning mechanisms at four sensitive receptor populations that underlie subtle differences in behavioral profiles of benzodiazepine site ligands.

The complex clinical picture of mono-neuropathy following injury of peripheral nerve is often accompanied by changes in the patients' affective states. It has been shown that positive allosteric modulators of GABAA receptors can decrease nociceptive transmission in animal pain models. However, recent findings suggest a possibility that at least some of the antinociceptive effects of benzodiazepines, related to neuropathic painful stimuli, may to a significant degree be a consequence of their anxiolytic action. In this study we evaluated the possible delayed effects of SH-I-048A, a newly- synthesized high-efficacy nonselective positive modulator of GABAA receptors, on anxiety-like behavior and locomotor activity in Wistar rats with a previously induced peripheral nerve injury. Assessment of behavioral parameters, using spontaneous locomotor activity and elevated plus maze tests, was performed 48h after completion of single-day three i.p. injections treatment consisting of zero, one, two or three doses of SH-I-048A (10 mg/kg). In general, rats' behavior observed 72 h after a moderate peripheral nerve injury did not indicate the persistence of sequelae of mono-neuropathic pain. The rats treated with three doses of SH-I-048A displayed an enhanced immobility time in the locomotor activity test, without concomitant decrease of the total distance traveled. On the other hand, in the group treated with two doses of SH-I-048A, a decrease in the emotional reactivity in the elevated plus maze test was observed. Subtle changes in the regimen of dosing of SH-I-048A affect locomotor activity and anxiety-related behavior in animals with peripheral nerve injury., Kompleksna klinička slika neuropatije nakon povrede perifernog nerva često je praćena i promenama afektivnog stanja pacijenata. U animalnim modelima bola pokazano je da pozitivni alosterni modulatori GABAA receptora mogu da smanje nociceptivnu transmisiju. Međutim, skorašnji nalazi ukazuju i na mogućnost da je prividni antinociceptivni efekat benzodiazepina nakon delovanja akutnog bolnog stimulusa u značajnoj meri posledica anksiolitičnog efekta. U ovoj studiji ispitani su mogući odloženi efekti novosintetisanog, neselektivnog liganda GABAA receptora (SH-I-048A) na lokomotornu aktivnost i ponašanje u vezi sa anksioznošću kod pacova soja Wistar prethodno podvrgnutih povredi perifernog nerva. Procena bihejvioralnih parametara sprovedena je testovima spontane lokomotorne aktivnosti i uzdignutog plus lavirinta 48 sati nakon što su životinje u periodu od 24 sata primile rastvarač, jednu, dve ili tri doze SH-I-048A (10 mg/kg). Generalno, ponašanje pacova praćeno 72 sata nakon umerene povrede perifernog nerva nije ukazivalo na prisustvo perzistentnih posledica neuropatskog bola. Pacovi prethodno tretirani sa tri doze SH-I-048A ispoljili su povećano vreme imobilnosti u testu lokomotorne aktivnosti, bez značajnog smanjenja ukupnog pređenog puta. S druge strane, u grupi koja je tretirana sa dve doze SH-I-048A zapažena je smanjena emocionalna reaktivnost u uzdignutom plus lavirintu. Kod životinja sa povredom perifernog nerva, suptilne razlike u režimu doziranja pozitivnog modulatora GABAA, mogu značajno da utiču na ponašanje vezano za lomotornu aktivnost i nivo anksioznosti.

Inverse agonism at the benzodiazepine site of alpha(5) subunit-containing GABA(A) receptors is an attractive approach for the development of putative cognition-enhancing compounds, which are still far from clinical application. Several ligands with binding and/or functional selectivity for alpha(5) GABA(A) receptors have been synthesized and tested in a few animal models. PWZ-029 is an alpha(5) GABA(A) selective inverse agonist whose memory enhancing effects were demonstrated in the passive avoidance task in rats and in Pavlovian fear conditioning in mice. In the present study we investigated the effects of PWZ-029 administration in novel object recognition test and Morris water maze, in normal and scopolamine-treated rats. All the three doses of PWZ-029 (2,5 and 10 mg/kg) improved object recognition after the 24-h delay period, as shown by significant differences between the exploration times of the novel and old object, and the respective discrimination indices. PWZ-029 (2 mg/kg) also successfully reversed the 0.3 mg/kg scopolamine-induced deficit in recognition memory after the 1-h delay. In the Morris water maze test, PWZ-029 (5,10 and 15 mg/kg) did not significantly influence swim patterns, either during five acquisition days or during the treatment-free probe trial. PWZ-029 (2, 5 and 10 mg/kg) also proved to be ineffective in the reversal of the 1 mg/kg scopolamine-induced memory impairment in the water maze. The present mixed results encourage use of a variety of tests and experimental conditions in order to increase the predictability of preclinical testing of selective as GABA(A) inverse agonists.

Over the last years, genetic studies have greatly improved Our knowledge on the receptor subtypes mediating various pharmacological effects of positive allosteric modulators at GABA(A) receptors. This stimulated the development of new benzodiazepine (BZ)-like ligands, especially those inactive/low-active at GABA(A) receptors containing the alpha(1) subunit, with the aim of generating more selective drugs. Hereby, the affinity and efficacy of four recently synthesized BZ site ligands: SH-053-2'N, SH-053-S-CH3-2'F, SH-053-R-CH3-2'F and JY-XHe-053 were assessed. They were also studied in behavioral tests of spontaneous locomotor activity, elevated plus maze, and water maze in rats, which are considered predictive of. respectively, the sedative, anxiolytic, and amnesic influence of BZs. The novel ligands had moderately low to low affinity and mild to partial agonistic efficacy at GABA(A) receptors containing the a, subunit, with variable, but more pronounced efficacy at other BZ-sensitive binding sites. While presumably alpha(1) receptor-mediated sedative effects of GABA(A) modulation were not fully eliminated with any of the ligands tested, only SH-053-2'N and SH-053-S-CH3-2'F, both dosed at 30 mg/kg, exerted anxiolytic effects. The lack of clear anxiolytic-like activity of JY-XHe-053, despite its efficacy at alpha(2)- and alpha(3)-GABA(A) receptors, may have been partly connected with its preferential affinity at alpha(5)-GABA(A) receptors coupled with weak agonist activity at alpha(1)-containing subtypes. The memory impairment in water-maze experiments, generally reported with BZ site agonists, was completely circumvented with all four ligands. The results suggest that a substantial amount of activity at a I GABA(A) receptors is needed for affecting spatial learning and memory impairments, while much weaker activity at alpha(1) and alpha(5)-GABA(A) receptors is sufficient for eliciting sedation.

The clinical use of benzodiazepines (BZs) is hampered by sedation and cognitive deterioration. Although genetic and pharmacological studies suggest that alpha(1)- and alpha(5)-containing GABA(A) receptors mediate and/or modulate these effects, their molecular substrate is not fully elucidated. By the use of two selective ligands: the alpha(1)-subunit affinity-selective antagonist beta-CCt, and the alpha(5)-subunit affinity- and efficacy-selective antagonist XLi093, we examined the mechanisms of behavioural effects of diazepam in the tests of spontaneous locomotor activity and water-maze acquisition and recall, the two paradigms indicative of sedative- and cognition-impairing effects of BZs, respectively. The locomotor-activity decreasing propensity of diazepam (significant at 1.5 and 5 mg/kg) was antagonized by beta-CCt (5 and 15 mg/kg), while it tended to be potentiated by XLi093 in doses of 10 mg/kg, and especially 20 mg/kg. Diazepam decreased acquisition and recall in the water maze, with a minimum effective dose of 1.5 mg/kg. Both antagonists reversed the thigmotaxis induced by 2 mg/kg diazepam throughout the test, suggesting that both GABA(A) receptor subtypes participate in BZ effects on the procedural component of the task. Diazepam-induced impairment in the declarative component of the task, as assessed by path efficiency, the latency and distance before finding the platform across acquisition trials, and also by the spatial parameters in the probe trial, was partially prevented by both, 15 mg/kg beta-CCt and 10 mg/kg XLi093. Combining a BZ with beta-CCt results in the near to control level of performance of a cognitive task, without sedation, and may be worth testing on human subjects.