The effect of estradiol on the alterations in monoamine-mediated behavioural responses induced by administration of electroconvulsive shocks or imipramine to female rats.

Female rats were treated daily with electroconvulsive shocks (ECS) or imipramine (10 mg/kg) for 10 days. Both types of treatment enhanced behavioural responses mediated by 5-hydroxytryptamine (5-HT) and noradrenaline (NA). A behavioural response mediated by dopamine (DA) was enhanced by electroconvulsive shock-treatment alone. On the other hand, rats treated only once with imipramine exhibited reduced DA-mediated behaviour. Priming the rats with estradiol valerate before starting electroconvulsive shock- or imipramine- treatment did not produce any significant effect on the enhancement in the behavioural response mediated by 5-HT. The enhancement in behaviour mediated by NA caused by electroconvulsive shock was also not altered, but that caused by treatment with imipramine was abolished. Enhancement of behaviour mediated by DA following electroconvulsive shock-treatment was also attenuated, while there was a positive reduction in behaviour mediated by DA in imipramine-treated rats. The two therapeutic approaches to depression, viz., electroconvulsive shock and imipramine, thus produced somewhat different effects on the central functions mediated by monoamines. Furthermore, an estrogen given prior to the treatments differentially altered the influence exerted by electroconvulsive shock and imipramine on monoamine functions in brain. The results may be pertinent to the clinical impression that estrogens produce a partial resistance to the antidepressant efficacy of imipramine-like drugs.