Anorexigenic effects of d-amphetamine and l-DOPA in the rat.
The effect of amphetamine and l-dopa was compared in 22-hr food- and water-deprived rats. Amphetamine produced marked anorexia, and l-dopa significantly reduced food intake at 200 mg/kg. Following pretreatment with RO 4-4602, a decarboxylase inhibitor, 100 mg/kg of l-dopa, a dose that did not significantly affect eating, produced marked anorexia. The anorectic effect of both amphetamine and l-dopa was antagonized by propranolol, a beta adrenergic antagonist. Phentolamine, an alpha-adrenergic antagonist, potentiated the anorectic effect of amphetamine and l-dopa. Haloperidol (0.1 mg/kg), a dopamine antagonist, failed to prevent the anorexia due to amphetamine but accentuated that due to l-dopa. Methysergide, a serotonin antagonist, also failed to prevent the anorexigenic effect of amphetamine. Finally, the administration of l-dopa with or without peripheral decarboxylase inhibition resulted in more than twice the increase in hypothalamic dopamine levels without significant changes in 5-HT or norepinephrine levels. The data show that the anorexigenic effect of amphetamine and l-dopa are similar and indicate a functional role for both norepinephrine and dopamine neurons in feeding behaviour in the rat.
D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D001067:Appetite Depressants; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors; D003913:Dextroamphetamine / Q000494:pharmacology*; D004295:Dihydroxyphenylalanine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior / Q000187:drug effects*; D006220:Haloperidol / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D013997:Time Factors
D000963:Antimetabolites; D001067:Appetite Depressants; D006834:Hydrazines; D012701:Serotonin; D004295:Dihydroxyphenylalanine; D011433:Propranolol; D002262:Carboxy-Lyases; D006220:Haloperidol; D003913:Dextroamphetamine; D009638:Norepinephrine; D008784:Methysergide; D010646:Phentolamine