Inhibition of morphine tolerance and dependence by Withania somnifera in mice.

Chronic treatment with Withania somnifera (Ws) (family: Solanaceae, 100 mg/kg) commercial root extract followed by saline on days 1-9 failed to produce any significant change in tailflick latency from the saline pretreated group in mice. However, repeated administration of Ws (100 mg/kg) for 9 days attenuated the development of tolerance to the analgesic effect of morphine (10 mg/kg). Ws (100 mg/kg) also suppressed morphine-withdrawal jumps, a sign of the development of dependence to opiate as assessed by naloxone (2 mg/kg) precipitation withdrawal on day 10 of testing.