Dopaminergic involvement in the effects of piracetam on foot shock induced aggression in mice

The effects of piracetam-a nootropic drug, were studied on foot shock induced aggressive behaviour in mice. Intraperitoneal injection of piracetam resulted in a biphasic response i.e.; initial excitation followed by inhibition of the aggressive behaviour. The initial excitation was observed with only 100 and 50 mg/kg doses of piracetam and not with the lower doses (25 and 12.5 mg/kg). Dopaminergic receptor blocker haloperidol (0.5; 0.25 and 0.12 mg/kg, ip) and pimozide (1.0 mg/kg, ip) produced inhibition of the aggressive behaviour. Lowering of the dose of haloperidol to 0.06 mg/kg resulted in an excitation of the aggressive behaviour. No motor deficit or catalepsy was observed with either haloperidol or pimozide injected in the doses indicated above. Pretreatment of the mice with haloperidol (0.12; 0.25 and 0.5 mg/kg) led to a dose-dependent blockade of the piracetam (100 mg) induced excitation of the aggressive behaviour, but the inhibition of the aggressive behaviour was not blocked by pretreatment with the excitatory dose of haloperidol. Similarly, pimozide (1.0 mg/kg) pretreatment also effectively blocked the excitatory effect of piracetam on aggressive behaviour. The results suggest the involvement of dopaminergic system in the excitatory effects of piracetam on aggressive behaviour. The inhibitory effect of piracetam appears to be independent of this mechanism.