Sedation and sleep induced by high doses of apomorphine after blockade of D-1 receptors by SCH 23390.
The effect of SCH 23390, a selective blocker of D-1 receptors, on apomorphine-induced behavioural and EEG changes was studied in rats. In control rats, a low dose of apomorphine (50 micrograms/kg s.c.) produced sedation associated with EEG synchronization. A high dose of apomorphine (1 mg/kg s.c.) produced stereotypy associated with EEG desynchronization. At the dose of 1 mg/kg i.p., SCH 23390 decreased motor activity but failed to alter the EEG pattern. The administration of either the low or high dose of apomorphine to SCH 23390-treated rats elicited a marked sedative response associated with EEG synchronization. The EEG synchronization produced by apomorphine (50 micrograms/kg) in SCH 23390-treated rats was prevented by (-)-sulpiride (25 mg/kg i.p.), a D-2 receptor blocker. It is concluded that by preventing the excitatory response to apomorphine SCH 23390 discloses the existence of a population of D-2 receptors mediating sedation and sleep.
Gessa
G L
GL
Porceddu
M L
ML
Collu
M
M
Mereu
G
G
Serra
M
M
Ongini
E
E
Biggio
G
G
D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D001058:Apomorphine / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology*; D004569:Electroencephalography; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D012890:Sleep / Q000187:drug effects*; D013469:Sulpiride / Q000494:pharmacology
D014150:Antipsychotic Agents; D001552:Benzazepines; D006993:Hypnotics and Sedatives; D011954:Receptors, Dopamine; D013469:Sulpiride; D001058:Apomorphine