Cocaine and dopaminergic actions in rat neostriatum.
Electrophysiological experiments were conducted in vivo to characterize the involvement of dopamine in effects of cocaine at the cellular level. L-DOPA (preceded by carbidopa) evoked excitation and depression equally at 0.25 mg/kg; however, at 0.5 and 1.0 mg/kg depression in the basal rate of discharge predominated. Cocaine evoked similar responses. At 0.25 and 0.5 mg/kg excitation and depression were elicited in about equal proportion, while at 1.0 mg/kg depression was predominant. Cocaine-induced neuronal changes were reversible by haloperidol. In experiments with specific dopamine antagonists, cocaine-induced neuronal depression was blocked with the D1 antagonist, SCH 23390 at a dose of 0.25 mg/kg. The D2 antagonist, eticlopride, did not alter cocaine-induced depression in any specific manner. Excitation, following cocaine, was not altered by intervention with SCH 23390, yet it was blocked with the D2 antagonist eticlopride at a dose of 0.25 mg/kg. The duration of these changes was consistent with the observed duration of the psychotropic actions of cocaine.
Nantwi
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KD
Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201.
Schoener
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EP
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D003042:Cocaine / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D003864:Depression, Chemical; D004298:Dopamine / Q000502:physiology*; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006220:Haloperidol / Q000494:pharmacology; D007262:Infusions, Intravenous; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D017072:Neostriatum / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects; D011343:Procaine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000187:drug effects; D017448:Receptors, Dopamine D2 / Q000187:drug effects; D012457:Salicylamides / Q000494:pharmacology
D001552:Benzazepines; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D012457:Salicylamides; D007980:Levodopa; D011343:Procaine; D003042:Cocaine; D006220:Haloperidol; C045989:eticlopride; D004298:Dopamine