Repeated electroconvulsive shock: effect on sodium dependency and regional distribution of opioid-binding sites

The effects of single and repeated electroconvulsive shock (ECS) on the binding of [3H]diprenorphine to rat brain membranes was studied. Repeated but not single ECS significantly increased the Bmax of [3H]diprenorphine binding when measured in the absence but not in the presence of NaCl. On a regional basis the effect of ECS was greatest in the olfactory bulb, nucleus accumbens, and striatum. More modest increases were found in the hippocampus, amygdala, septum, hypothalamus, and pyriform cortex. No significant effect was found in the brainstem and frontal cortex. Although the regional rank order of receptor increase does not match the receptor distribution of brain enkephalins, the receptor increase does parallel the regional increases in brain enkephalins following ECS.