SKF 38393 and apomorphine modify locomotion and exploration in rats placed on a holeboard by separate actions at dopamine D-1 and D-2 receptors.
Horizontal motor activity, rearing and head dipping were recorded automatically in rats placed on a holeboard and taken as indices of locomotion and exploration. Other behaviours were assessed visually using a video camera. SKF 38393, 15-30 mg/kg (D-1 agonist), suppressed all three behavioural measures more effectively in habituated than in naive rats. These actions were blocked by SCH 23390 (0.05 mg/kg, D-1 antagonist) but not by haloperidol (0.05 mg/kg, D-2 antagonist). Apomorphine modified behaviour biphasically, causing haloperidol-resistant sedation at a low, presynaptic dose (0.05 mg/kg) and haloperidol-sensitive hyperactivity and stereotyped sniffing at a larger, postsynaptic dose (0.5 mg/kg, especially after habituation). Neither action was antagonised by SCH 23390. The results support the conclusion that D-1 and D-2 dopamine recognition sites can separately influence the processes controlling locomotion and exploratory activity in normal rats.
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D001067:Appetite Depressants / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology*; D005106:Exploratory Behavior / Q000187:drug effects*; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*
D001067:Appetite Depressants; D001552:Benzazepines; D011954:Receptors, Dopamine; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D006220:Haloperidol; D001058:Apomorphine