Repeated ECS enhances dopamine D-1 but not D-2 agonist-induced behavioural responses in rats

The present study examined the effect of acute and repeated administration of electroconvulsive shock (ECS) on behaviours induced by various dopamine agonists in rats. Components of behavioural arousal induced by the dopamine D-1 agonist SKF 38393, the dopamine D-2 agonist RU 24213 and the mixed D-1/D-2 agonist apomorphine were assessed using a behavioural check-list method. Also, the overall behavioural syndrome produced by these drugs was measured using rating scales. Rats receiving repeated (5 times over 10 days) but not a single ECS showed enhanced grooming and sniffing in response to SKF 38393 (7.5 mg/kg) when compared to controls. Repetitive sniffing induced by apomorphine (0.5 mg/kg) was also enhanced by repeated ECS. Neither repeated nor a single ECS significantly changed behaviours induced by RU 24213 (0.75 mg/kg), although a downward trend was evident. The behaviour rating scale measurements also demonstrated that repeated administration to ECS increased behavioural responsiveness to SKF 38393 and apomorphine but not RU 24213. These results suggest that the increase of dopamine-mediated behaviour in rats seen after chronic ECS relates to an increase in central dopamine D-1 receptor function.