5-HT2A receptor binding and antidepressant studies on Anximin®, a polyherbal formulation

Abstract

The objective of the present study was to carry out preclinical evaluation of the antidepressant activity of a polyherbal formulation Anximin. It consists of 5 medicinal plants namely: (i) Bacopa monnierae, (ii) Convolvulus pluricaulis, (iii) Rauwolfia serpentina, (iv) Nardostachys jatamansi and (v) Acorus calamus. Adult Charles foster albino rats (200±20g) and Wistar mice (25±5g), of either sex were used for the study. Antidepressant activity was assessed by using the validated models of depression viz. behavioural despair test (BDT), tail suspension test (TST), learned helplessness test (LHT) and yohimbine toxicity enhancement test (YTE). Since single acute administration of both the doses of Anximin (20 and 40 mg/kg) suspended in 0.3% CMC had no significant antidepressant effect, therefore it was given orally for 7 consecutive days. The standard drug imipramine (10 mg/ kg) was also administered for 7 consecutive days through oral route. All the behavioural experiments were performed 1 hr after last administration of drug on day 7. Immobility time in FST and TST was significantly (p < 0.01) reduced by the high dose (40 mg/kg) of Anximin treated animals, while low dose (20 mg/kg) has no significant effect. A significant (p < 0.001) decrease in number of escape failures in LHT was also observed in both groups of Anximin treated rats. In YTE test, the percentage of mortality of animals was 33% and 66% with both the doses (20 and 40 mg/kg respectively) of Anximin whereas in imipramine treated group mortality was 100%. To elucidate mechanism of action, a receptor binding study was also performed using rat's frontal cortex. The high dose (40 mg/kg) of Anximin treated group significantly (p < 0.05) decreased the binding level of 3 [H] ketanserin, indicating a downregulation of 5-HT2A receptors. The results indicate that Anximin possesses promising antidepressant activity acting through 5-HT2A receptors.