Electroconvulsive Shock and Brain Cholinergic Function: Role of Striatal Muscarinic Receptors

Repeated administration of electroconvulsive shock (ECS) has been reported to reduce (3)H-quinuclidinyl benzilate ((3)H-QNB) binding to muscarinic cholinergic receptors in rat brain. ECS-induced muscarinic receptor subsensitivity may play a role in the therapeutic or adverse mechanisms of electroconvulsive therapy (ECT). In the present report, cataleptic responses to the muscarinic agonist, pilocarpine, were studied as a functional measure of brain muscarinic receptor sensitivity after ECS. Both single and repeated ECS administration attenuated pilocarpine-induced catalepsy, suggesting functional subsensitivity of the muscarinic receptors mediating this response. However, parallel changes were not observed in striatal muscarinic receptor binding. While repeated ECS induced a small but significant reduction in (3)H-ONB binding, single ECS marginally increased binding. The effect of pretreatment with a cholinergic antagonist (scopolamine) and with a cholinesterase inhibitor, diisopropyl fluorophosphate (DFP), on cataleptic responses was also studied. The findings demonstrated functional cholinergic subsensitivity after DFP administration and supersensitivity after scopolamine pretreatment. A clear relationship between functional alterations in muscarinic receptor sensitivity and radioligand binding parameters was not, however, established. Possible reasons for this discrepancy are discussed.