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SELECTIVE INHIBITION OF RESPONSES TO CARBACHOL AND McN‐A‐343 IN THE RABBIT VAS DEFERENS
Author(s) -
Choo L. K.,
Mitchelson F.
Publication year - 1990
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1990.tb01361.x
Subject(s) - muscarine , carbachol , pirenzepine , chemistry , vas deferens , endocrinology , muscarinic acetylcholine receptor , stimulation , medicine , inhibitory postsynaptic potential , atropine , receptor , biochemistry
SUMMARY 1. The effect of several selective muscarine receptor antagonists were evaluated on the responses of carbachol (CCh) and McN‐A‐343 (McN) during sympathetic nerve stimulation in the rabbit vas deferens. 2. The muscarine M 1 receptor antagonist pirenzepine exhibited similar apparent pK B values for antagonism of the prejunctional inhibitory response of either CCh (pK B , 8.2) or McN (pK B , 8.5) on sympathetic nerve stimulation. 3. The muscarine M 2 receptor antagonists, pancuronium and the bisalkyl ammonium compound ‘C 7 /3‐phth’ were selective inhibitors of the postjunctional facilitatory response produced by CCh on sympathetic nerve stimulation. They were also 17‐and three‐fold, respectively, less potent against the inhibitory responses of McN on sympathetic nerve stimulation. The apparent pK B value of pancuronium on the inhibitory response produced by CCh did not differ significantly ( P >0.05) from that using McN. A similar finding was made for C 7 /3‐phth. 4. Selective blockade of the inhibitory response to CCh with pirenzepine (0.03 or 0.5 μmol/L) did not significantly ( P >0.05) modify the apparent pK B value for pancuronium on the facilitatory response of CCh. 5. Selective blockade of the facilitatory response to CCh with a low concentration of pancuronium (0.5 μmol/L) did not significantly ( P >0.05) modify the apparent pK B value for pancuronium (30 μmol/L) on the inhibitory response of CCh. 6. It is suggested that CCh and McN activate the same prejunctional M 1 muscarine receptor and that pancuronium is the most selective of the muscarine M 2 receptor antagonists presently tested in this preparation for distinguishing between muscarine M 1 and M 2 receptors.