Analgesic activity of a Withania somnifera extract in stressed mice

Abstract

Withania somnifera is an important Ayurvedic Rasayana herb, the roots of which are often used in traditionally known systems of medicine as tonic or for rejuvenation purposes. Effects of a single and ten daily oral doses (10, 20 and 40 mg/kg) of an analytically well standardized Withania somnifera root extract against foot shock stress triggered transient hyperthermia and hotplate test for analgesics in male mice were quantified. Body weights and basal rectal temperatures of animals were recorded on all observational days and on the 11th and 12th day of the experiment, all animals were subjected to tail suspension and pentobarbital hypnosis tests respectively. Daily dose dependent efficacy of the tested extract in stress induced hyperthermia test and in hot plate test increased with increasing number of treatment days, and its dose dependent inhibitory effect on immobility time in tail suspension were observed after its 11 daily oral doses. Daily handling and intermittent foot shock stress triggered body weight losses and elevations in basal core temperatures were almost completely prevented even by its lowest daily dose (10 mg/kg/day) tested. Repeated daily low oral doses of the Withania somnifera extract is effective in suppressing diverse stress responses, and its centrally acting analgesics and anxiolytics or antidepressants like efficacies increase with increasing numbers of treatment days. These observations reaffirm that Withania somnifera is an adaptogenic herb, and suggest that its effective therapeutic doses has to be adjusted according to the pre-existing allostatic load of patients.