Effect of electroconvulsive shock treatment on the opioid-mediated inhibition of serotonin release in rat hippocampal slices.

We investigated the influence of electroconvulsive shock treatment on the opioid-mediated inhibition of serotonin (5-HT) release. The overflow of [3H]serotonin elicited by high potassium (30 mM) in superfused slices of rat hippocampus was significantly inhibited in the presence of two agonists, mu-selective [D-Ala2,N-methyl-Phe4,Gly5ol]enkephalin (DAGO) and delta-selective [D-Pen2,D-Pen5]enkephalin (DPDPE) in control animals. The repeated (once daily for 7 days) electroconvulsive shock treatment significantly reversed the inhibitory effect of both DAGO and DPDPE. Single electroconvulsive shock (1 day) had no effect on DAGO inhibition, on the contrary a trend to antagonism of the DPDPE effect was reported. These results suggested that the opioids are associated with the experimental induced seizures and that the ECS treatment might regulate the serotonin release throughout the opioid receptor system.