Effects of the muscarinic agonist McN-A-343 on responses to sympathetic nerve stimulation in the rabbit ear artery.
1. Observations were made on the effects of 4-(m-chlorophenylcarbamoyloxy)-2-butynyltrimethylammonium chloride (McN-A-343) on responses of isolated segments of the central artery of the rabbit's ear to sympathetic nerve stimulation and noradrenaline.2. With low frequencies of nerve stimulation (2-5 Hz), McN-A-343 caused a decrease in responses to sympathetic nerve stimulation. This effect of McN-A-343 was abolished by dexamphetamine or atropine. In the presence of atropine, McN-A-343 caused an increase in responses to sympathetic nerve stimulation.3. With high frequencies of nerve stimulation (10-20 Hz), McN-A-343 caused an increase in responses. This effect was not qualitatively changed in the presence of atropine.4. When McN-A-343 had an inhibitory effect on responses to sympathetic nerve stimulation, responses to noradrenaline were unaffected.5. It is suggested that McN-A-343 acts on muscarinic receptors through which noradrenaline release may be inhibited; it may also act on the cholinergic stage in adrenergic transmission postulated by Burn & Rand (1959).
D000818:Animals; D001158:Arteries / Q000187:drug effects* / Q000294:innervation; D001285:Atropine / Q000494:pharmacology; D002219:Carbamates / Q000494:pharmacology*; D003913:Dextroamphetamine / Q000494:pharmacology; D004431:Ear, External / Q000098:blood supply; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000187:drug effects*
D002219:Carbamates; D010277:Parasympathomimetics; D000644:Quaternary Ammonium Compounds; D001285:Atropine; D003913:Dextroamphetamine; D009638:Norepinephrine