[Effects of dopamine receptor agonists and antagonists on cocaine-induced behaviors in rats].
In this study, cocaine (5-20 mg/kg), an indirect dopamine agonist, increased locomotor activity and rearing accompanied with head circling and body shaking in a dose-dependent manner. A high dose of cocaine (40 mg/kg), meaning a toxic dose, slightly induced sniffing and licking. Both SCH23390, a D-1 receptor antagonist, and raclopride, a D-2 antagonist, inhibited all behaviors induced by cocaine, suggesting that the behavioral actions of cocaine may involve the activation of D-1 and D-2 receptors. Selective D-2 agonist quinpirole (0.1 and 1.0 mg/kg) inhibited hyperlocomotion induced by cocaine (20 mg/kg), but was replaced by the typical stereotyped behaviors such as sniffing at low dose (0.1 mg/kg), and licking and gnawing at high dose (1.0 mg/kg). SK & F38393, a selective D-1 agonist, in combination of cocaine did not induce these stereotyped behaviors which resulted in synergistic interaction of D-1 and D-2 receptor stimulation. These results suggest that the indirect stimulation of postsynaptic D-2 receptors by cocaine (20 mg/kg) was insufficient to induce stereotyped behaviors. The actions of cocaine on dopamine D-1 receptors seem to be more potent than that on D-2 receptors.
Minematsu
N
N
Department of Neuropsychiatry, Yamaguchi University School of Medicine, Ube, Japan.
Ushijima
I
I
Obara
N
N
Mizuki
Y
Y
Yamada
M
M
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001552:Benzazepines / Q000494:pharmacology*; D003042:Cocaine / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D008124:Locomotion / Q000187:drug effects; D008297:Male; D020891:Raclopride; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors*; D012457:Salicylamides / Q000494:pharmacology*; D013239:Stereotyped Behavior / Q000187:drug effects
D001552:Benzazepines; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D012457:Salicylamides; D020891:Raclopride; D003042:Cocaine