Synergistic effect of Withania somnifera Dunal and L-dopa in the inhiition of haloperidol-induced catalepsy in mice

The possible synergism between WS and dopamine precursor L-dopa to inhibit haloperidol-induced catalepsy was investigated by using standard bar test in mice. The effect of WS (20–200 mg/kg, oral), L-dopa (20–200 mg/kg, oral) plus carbidopa and combination of subeffective doses of WS (20 or 50 mg/kg, oral) prior to L-dopa (20, 50 or 100 mg/kg, oral) plus carbidopa was assessed in haloperidol (1 mg/kg, i.p.) induced catalepsy. L-dopa and carbidopa combination was always administered in 10:1 ratio. WS (100 or 200 mg/kg, oral) and L-dopa (50, 100 or 200 mg/kg, oral) plus carbidopa treated groups showed a dose dependent reduction in cataleptic scores. Subeffective doses of WS (20 or 50 mg/kg, oral) prior to L-dopa (20, 50 or 100 mg/kg, oral) also potentiated the anticataleptic effect of L-dopa. These results indicate that subeffective doses of WS enhance the anticataleptic actions of L-dopa and the possibility of using WS as adjunctive therapy to reduce the doses and the adverse effects of dopamine precursor in Parkinson’s disease.