Repeated electroconvulsive shocks and the brain content of endorphins.

Repeated electroconvulsive shocks (ECS) cause an increase of [met5]-enkephalin (ME) content in hypothalamus and some limbic areas such as n. accumbens, septum and amygdala. The temporal characteristics of this increase resemble the time course of the clinical effects of electroconvulsive therapy (ECT). Single shock failed to change the ME content in any part of the brain. After 6 daily shocks ME content increases by 60% in hypothalamus and maximal effect (100% increase) was obtained after 10 daily shocks. The increase of ME content persists 6 days after the termination of ECS. Subconvulsive shocks failed to alter the content of ME in all the brain gions determined. When the seizure induced by ECS was prevented by pretreatment with an anesthetic dose of phenobarbital, the ECS-induced increase in hypothalamic and septal ME content was also blocked. beta-Endorphin content of hypothalamus remained unchanged after repeated ECS despite a two-fold increase in the ME content in the same region. These observations indicate that the time constant for the increase in ME content induced by ECS resembles the time constant for the appearance of the clinical benefits by ECT and may give credence to the possibility that the ME increase may participate in the antidepressive action of ECS.