Repeated electroconvulsive shock prevents the sedative effect of small doses of apomorphine

Repeated electroconvulsive shock (ECS) (one shock daily for 8 days), but not single ECS, eliminates the sedative response to small doses of apomorphine (25--1000 microgram/kg) and potentiates the stimulant response to high doses (200 microgram/kg) of the drug in rats. This effect is observed 1 and 4 days after the last ECS. However, repeated ECS does not prevent the inhibitory effect of apomorphine on dopamine (DA) synthesis. The results suggest that repeated ECS may lead to the development of subsensitivity in DA receptors that mediate sedation and that these receptors are differentiated from those controlling DA synthesis.