Effects of repeated electroconvulsive shocks on catecholamine systems: electrophysiological studies in the rat brain

Electroconvulsive therapy (ECT) treats depression by repeated administration of seizure-inducing electrical stimuli. To assess the effects of repeated electroconvulsive shocks (ECSs), an animal model of ECT on monoamine transmission, Sprague-Dawley rats were administered 6 ECS over 2 weeks and in vivo single-unit extracellular electrophysiological recordings were obtained 48 h after the final ECS. Overall firing activity of dopamine (DA) neurons in the ventral tegmental area was unchanged following repeated ECS. In the locus coeruleus (LC), the burst activity of norepinephrine (NE) neurons was increased while population activity was decreased after ECS. In the substantia nigra pars compacta (SNc), there were more spontaneously active neurons, suggesting greater DA tone in the nigrostriatal motor pathway, which may contribute to an alleviation of motor retardation. In the facial motor nucleus (FMN), facilitation of electrophysiological activity by serotonin (5-HT), and NE was determined to be through the 5-HT2C receptor and α1 -adrenoceptor, respectively. Locally administered NE, but not 5-HT, facilitated glutamate-induced firing following repeated ECS, which may contribute to improved motor function. These results showed that repeated ECS enhance DA activity in the SNc and NE transmission in the FMN, which could be a part of the mechanism behind the alleviation of depressive symptoms, including motor retardation, by ECT.