Effect of Emblica officinalis tannoids on a rat model of tardive dyskinesia

Effect of active tannoid principles of E. officinalis, comprising of emblicanin A (37%), emblicanin B (33%), punigluconin (12%) and pedunculagin (14%), was investigated on a rat model of tardive dyskinesia (TD) induced by once daily administration of haloperidol (1.5 mg/kg, ip) for 28 days. Involuntary orofacial movements (chewing movements, buccal tremors and tongue protusion) were assessed as TD parameters. The tannoid principles of E. officinalis (EOT) were administered concomitantly with haloperidol in the doses of 10, 20 and 50 mg/kg, po, for 28 days. Sodium valproate (200 mg/kg, po), a Gaba-mimetic agent, and vitamin E (400 mg/kg, po), an antioxidant, were used as the standard drugs and administered for the same period. EOT induced a dose-related inhibition of all the three TD parameters assessed, as did vitamin E. The effect of sodium valproate remained statistically insignificant. The results suggest that EOT exerts a prophylactive effect against neuroleptic-induced TD which is likely to be due to its earlier reported antioxidant effects in rat brain areas, including striatum.