βCCT, an antagonist selective for α1GABAA receptors, reverses diazepam withdrawal-induced anxiety in rats

Abstract

The abrupt discontinuation of prolonged benzodiazepine treatment elicits a withdrawal syndrome with increased anxiety as a major symptom. The neural mechanisms underlying benzodiazepine physical dependence are still insufficiently understood. Flumazenil, the non-selective antagonist of the benzodiazepine binding site of GABAA receptors was capable of preventing and reversing the increased anxiety during benzodiazepine withdrawal in animals and humans in some, but not all studies. On the other hand, a number of data suggest that GABAA receptors containing α1 subunits are critically involved in processes developing during prolonged use of benzodiazepines, such are tolerance to sedative effects, liability to physical dependence and addiction. Hence, we investigated in the elevated plus maze the level of anxiety 24 h following 21 days of diazepam treatment and the influence of flumazenil or a preferential α1-subunit selective antagonist βCCt on diazepam withdrawal syndrome in rats. Abrupt cessation of protracted once-daily intraperitoneal administration of 2 mg/kg diazepam induced a withdrawal syndrome, measured by increased anxiety-like behavior in the elevated plus maze 24 h after treatment cessation. Acute challenge with either flumazenil (10 mg/kg) or βCCt (1.25, 5 and 20 mg/kg) alleviated the diazepam withdrawal-induced anxiety. Moreover, both antagonists induced an anxiolytic-like response close, though not identical, to that seen with acute administration of diazepam. These findings imply that the mechanism by which antagonism at GABAA receptors may reverse the withdrawal-induced anxiety involves the α1 subunit and prompt further studies aimed at linking the changes in behavior with possible adaptive changes in subunit expression and function of GABAA receptors.

Novel Benzodiazepine-Like Ligands with Various Anxiolytic, Antidepressant, or Pro-Cognitive Profiles

“…Using validated screening tests, we showed that the ligands display unique therapeutic profiles, including anxiolytic- and antidepressant-predictive properties, and pro-cognitive properties in GL-II-73, reversing stress-induced and age-related working memory deficits. The three novel ligands displayed reduced side effects compared to DZP (such as sedation and amnesia), consistent with reduced α1 potentiation [40-42]. …”

Development and evaluation of liposomal formulation containing nimodipine on anxiolytic activity in mice

“…Flumazenil was used in the experiment because it is a nonselective antagonist of the benzodiazepine binding site of GABAA receptors (Divljakovi'c et al, 2013). Its administration assists in elucidating the mechanism of action of the formulation, since the possible decrease in anxiolytic effects in animals treated with flumazenil before receiving NMD-Lipo, and the resulting channel antagonism of benzodiazepines, is indicative of the action of nanoencapsulated nimodipine in such receptors.…”

Duration of treatment and activation of α1-containing GABAA receptors variably affect the level of anxiety and seizure susceptibility after diazepam withdrawal in rats

“…In accordance with the suggested longer duration of action of βCCt (Zhang et al, 1995; June et al, 2003), its brain concentration of about 55 nmol/kg, measured 16 h after the last dose in protracted (twice daily for 14 days) administration of βCCt with diazepam (Savić et al, unpublished data), implies that βCCt in the present work was sufficient to prevent binding of diazepam at α 1 -containing GABA A receptors, without affecting the withdrawal behavior. Finally, it is noteworthy that in the current study the compounds were dissolved in the same solvent as used in our previous behavioral and pharmacokinetic studies (Divljaković et al, 2012; Divljaković et al, 2013; Savić et al, unpublished data).…”

“…Such an adaptive behavioral response was not observed in our previous studies, when the protracted i.p . administration of treatment has been also applied (Divljaković et al, 2012: Divljaković et al, 2013). The subtle differences in the experimental design, such as co-administration of two injections in the present, instead of one injection in previous studies, could have favored the development of the increased locomotion after 21 days of treatment.…”

“…Additionally, using different subtype selective positive allosteric modulators with reduced efficacy, Ator et al (2010) and Mirza and Nielsen (2006) have shown that lack of efficacy at the α 1 -containing GABA A receptors, probably coupled with the reduced efficacy at the α 2 - and α 3 -containing receptors, led to reduced physical dependence liability in baboons and mice, respectively. Moreover, a recent study from our group has demonstrated the significant involvement of α 1 -containing GABA A receptors in the manifestation of increased anxiety during withdrawal (Divljaković et al, 2013). …”