Actions of clonidine on convulsions and behaviour.

Pretreatment of rats and mice with clonidine (0.5-5 mg/kg, intraperitoneally) protected the animals against tonic convulsions induced by picrotoxin, strychnine and maximal electroshock, respectively. The time of onset of convulsions as well as mortality due to picrotoxin and strychnine were delayed in the clonidine pretreated groups as compared to controls. Clonidine (1 mg/kg) blocked the extensor phase of the electroshock convulsion. In reserpinized animals the severity of electroshock-induced seizures was reduced by clonidine pretreatment. Clonidine also caused an increase in the food consumption behaviour in mice subjected to novel situation and food. Its effects were comparable to diazepam, an antianxiety agent. In another experiment, clonidine (0.5-5 mg/kg) counteracted the perphenazine-induced catatonia in rats. It is possible that the observed anticatatonic effect of clonidine may be due to its presynaptic activity, but the actual mechanism of this action is not yet understood.