Mechanisms of action of dopamine in the peripheral nervous system of chicks and rats.
The effects and mechanisms of action of dopamine on the lower oesophagus and expansor secundariorum muscle (ESM) of chicks and on the bladder of rat have been examined. Dopamine contracted the lower oesophagus in a concentration-related fashion but failed to contract the muscle from chicks pretreated with reserpine or p-chlorophenylalanine. Contraction of the ESM by dopamine was antagonized by prazosin but not by propranolol. Supersensitivity of the ESM to dopamine observed 3 or 28 days after surgical denervation of the muscle was comparable. Dopamine did not exert any agonist effect on the rat bladder but depressed responses to stimulation of non-adrenergic, non-cholinergic (NANC) nerves in the bladder. These findings indicate that dopamine contracts the upper oesophagus of chicks by releasing 5-hydroxytryptamine, activates alpha-adrenergic receptors causing contraction of the ESM but depresses NANC neurotransmission in the bladder.
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Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmaceutical Sciences, University of Jos, Nigeria.
D000818:Animals; D002645:Chickens; D003714:Denervation; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004558:Electric Stimulation; D004947:Esophagus / Q000187:drug effects / Q000294:innervation; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D009638:Norepinephrine / Q000494:pharmacology; D017933:Peripheral Nervous System / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D001743:Urinary Bladder / Q000187:drug effects / Q000294:innervation
D018492:Dopamine Antagonists; D007545:Isoproterenol; D004298:Dopamine; D009638:Norepinephrine