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Characterization of pre‐ and postsynaptic muscarinic receptors in circular muscle of pig gastric fundus
Author(s) -
Leclere Pascal G,
Lefebvre Romain A
Publication year - 2002
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0704582
Subject(s) - muscarinic acetylcholine receptor , endocrinology , medicine , methoctramine , postsynaptic potential , muscarinic acetylcholine receptor m2 , acetylcholine , muscarinic acetylcholine receptor m1 , chemistry , receptor , muscarinic acetylcholine receptor m3 , muscarinic acetylcholine receptor m4 , biology
This study investigated the subtype of muscarinic receptors on the cholinergic neurones and smooth muscle in the circular muscle of the pig gastric fundus. Muscarinic antagonists, except MT‐3, concentration‐dependently inhibited the contractions induced by a given concentration of acetylcholine. Concentration‐response curves by acetylcholine were shifted rightwards in a parallel manner without depression of the maximum by the muscarinic antagonists, except by MT‐3 that induced a leftward shift. Correlation of the pIC 50 and pA 2 values with published pK i values for the five muscarinic receptor subtypes suggests that the muscarinic receptors on pig gastric fundus circular muscle belong to the M 3 subtype. Electrically‐evoked contractions (40 V, 4 Hz, 0.25 ms, 2 min) were concentration‐dependently inhibited by the muscarinic antagonists except for methoctramine and AF‐DX 116, that increased the amplitude of the electrically‐induced contractions in lower concentrations. MT‐3 tended to increase the electrically‐induced contractions. The antagonists, except MT‐3, concentration‐dependently increased the electrically‐induced tritium outflow (40 V, 4 Hz, 0.25 ms, 2 min) after incubation of the tissues with [ 3 H]‐choline. MT‐3 (3×10 −8 and 10 −7 M ) decreased the electrically‐induced tritium release. Correlation of the pIC 50 values with published pK i values for the different muscarinic receptor subtypes yielded a significant and comparable correlation for M 1 , M 3 , M 4 and M 5 receptors. These results suggest that the postsynaptic receptors in circular muscle of the pig gastric fundus belong to the M 3 subtype. However, the presynaptic receptor could not be clearly defined, although it does certainly not belong to the M 2 subtype.British Journal of Pharmacology (2002) 135 , 1245–1254; doi: 10.1038/sj.bjp.0704582