Effects of stimulation of dopamine D1 receptors on the cortical EEG in rats: different influences by a blockade of D2 receptors and by an activation of putative dopamine autoreceptors.

The effects of a stimulation of dopamine D1 receptors by using (+/-)SKF 38393 on the cortical EEG in rats which were chronically implanted with electrodes were studied. Administration of SKF 38393 (3 or 9 mg/kg, s.c.) produced alterations suggesting an arousal in the EEG: the power in all of the frequency bands decreased to a level of 70-80% of baseline activity, which effect was dose- and time-dependent. In behaviour, episodes of intensive grooming (face-washing) alternated with those of lack of spontaneous motility and occasionally chewing movements were noted. In contrast, apomorphine (0.5 mg/kg, s.c.) produced a selective increase in power in the alpha 1 band, accompanied by stereotyped sniffing and licking. The effects of SKF 38393 (9 mg/kg) were completely blocked by pretreatment with the selective antagonist at D1 dopamine receptors, SCH 23390 (0.2 mg/kg, i.p.). The application of haloperidol (0.1 mg/kg, i.p.), which is mainly a D2 blocker, failed to influence the alterations induced by SKF 38393 (9 kg/kg, s.c.). In a further experimental group, the effects produced by stimulation of D1 receptors (SKF 38393 9 mg/kg), followed by activation of putative dopamine autoreceptors by a small dose of apomorphine (0.05 mg.kg, s.c.) were studied: in this case, the effects of SKF 38393 were abolished and typical effects of small doses of apomorphine were manifest, such as hypokinesia and sedation, accompanied by large increases of power in all of the frequency bands, except beta 2. The results suggest that stimulation of D1 receptors produces some desynchronization in the EEG.(ABSTRACT TRUNCATED AT 250 WORDS)