Hypophysectomy does not prevent the enhanced monoamine-mediated behavioural responses following repeated...

Groups of hypophysectomised rats were given either an electroconvulsive shock (ECS; 125V, 1 sec) once daily for 10 days or a sham-shock. Twenty-four hours after the final treatment both groups were tested for their responses to the dopamine agonist, apomorphine, the 5-hydroxytryptamine agonist, quipazine, and the alpha 2-adrenoceptor agonist, clonidine. Repeated electroconvulsive shock enhanced the locomotor activity produced by either quipazine (25 mg/kg i.p.) or apomorphine (0.2 mg/kg s.c.) compared to sham-shocked controls. This treatment also attenuated the hypoactivity produced by clonidine (0.5 mg/kg i.p.). These changes are identical to those produced in normal rats by repeated electroconvulsive shock. Hypophysectomy, therefore, did not abolish the increased 5-hydroxytryptaminergic and dopaminergic behavioural responses neither did it prevent the decreased functional activity of central alpha 2-adrenoceptors, which may be presynaptic. These data suggest that although electroconvulsive shock has been reported to stimulate the secretion of various pituitary hormones, this process is not essential for the development of the enhanced monoamine-mediated behavioural responses studied.