title: Pre- and post-synaptic muscarinic receptors of the rat vas deferens: an update.
abstract: The pre- and post-synaptic muscarinic receptors of the rat vas deferens are not M1 since the M1-selective antagonist pirenzepine (PZ) has low affinity for both. On this basis both the pre- and post-synaptic actions of ACh in this preparation seem to be mediated via M2-like muscarinic receptors. The following experimental observations reveal that both responses are mediated by pharmacologically distinct muscarinic receptors. The rank order of potency displayed by 3 muscarinic antagonists (Atropine, N-methyl-scopolamine [NMS] and PZ) at each of these sites is different. Atropine and PZ are selective blockers of the post-synaptic smooth muscle muscarinic receptor. NMS is a selective antagonist of the pre-synaptic muscarinic receptor that facilitates norepinephrine's release. Finally, PZ and NMS are non-competitive and competitive antagonists, post- and pre-synaptically, respectively. The results suggest that the post-synaptic smooth muscle muscarinic receptor belongs to the M2B (or M3) subtypes. The pre-synaptic muscarinic receptor belongs to the M2A (or M2) subtypes or to a subclass of the M2B (or M3) muscarinic receptor subtypes.
authors.affiliation: Department of Pharmacology, Universidad Central del Caribe School of Medicine, Cayey, PR.
authors.forename: W I
authors.initials: WI
authors.lastname: Silva
authors.forename: W W
authors.initials: WW
authors.lastname: Wolstenholme
authors.forename: H I
authors.initials: HI
authors.lastname: Miranda
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000294:innervation*; D019832:N-Methylscopolamine; D009469:Neuromuscular Junction / Q000502:physiology*; D010890:Pirenzepine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000145:classification / Q000502:physiology*; D012602:Scopolamine Derivatives / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*; D009626:Terminology as Topic; D014649:Vas Deferens / Q000294:innervation
chemical_list: D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D010890:Pirenzepine; D001285:Atropine; D019832:N-Methylscopolamine