The inhibitory action of dopamine on the anterior tibialis muscle preparation antagonized by pimozide and chlorpromazine.
In the cat anterior tibialis muscle preparation dopamine produces a decrease on indirectly evoked twitch contraction when it is administered intraarterially but not on intravenous injection. Edrophonium (0.3 mg/kg) exerts only a brief antagonism to the dopamine-induced inhibition. The phenothiazine derivative, chlorpromazine (CPZ, 400 mug/kg) which possesses both alpha and dopaminergic blocking properties significantly reduces the action of dopamine on skeletal muscle. However, phentolamine (1 mg/kg), an alpha adrenergic blocker is without effect, possibly indicating that the dopaminergic blocking characteristic of CPZ is responsible for decreasing the action of dopamine. A more selective dopaminergic blocking agent, pimozide (100 and 200 mug/kg) is an effective antagonist to the paralysis caused by dopamine on the anterior tibialis muscle. The results of this investigation suggests the possibility that a dopaminergic receptor may be present in or on skeletal muscle.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D002746:Chlorpromazine / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004347:Drug Interactions; D004491:Edrophonium / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects*; D010646:Phentolamine / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology
D018492:Dopamine Antagonists; D010868:Pimozide; D004491:Edrophonium; D011433:Propranolol; D002746:Chlorpromazine; D004298:Dopamine; D010646:Phentolamine