Effects of chronic treatment with imipramine on the behavioural and electroencephalographic modifications induced by clonidine in the rat.

The influence of repeated administration of imipramine on the EEG and behavioural effects of clonidine has been studied in the rat bearing chronic electrodes. Clonidine induced behavioural depression and EEG synchronization in control rats. Mydriasis, hyperirritability, stereotyped behaviour and EEG desynchronization were elicited by clonidine on the first and second days after discontinuation of the treatment with imipramine (15 mg/kg, i.p., daily for 21 days). On the 9th. day the animals responded to clonidine with sedation and EEG synchronization. These results support the hypothesis that chronic treatment with tricyclic antidepressant drugs changes the sensitivity of central noradrenergic neurones.