Characterization of muscarinic receptors involved in tracheal CGRP release.
Application of acetylcholine (ACh) to isolated rat trachea induces an increase in calcitonin gene-related peptide (CGRP) outflow in the perfusates. The elevation of CGRP release by ACh was absent in capsaicin-desensitized preparations, suggesting that the release of peptide is derived from capsaicin-sensitive afferent nerves. ACh-induced release was not altered by hexamethonium, but was significantly attenuated by atropine, indicating involvement of the muscarinic receptor. Effects of three selective muscarinic subtype antagonists, pirenzepine (M1), methoctramine (M2) and 4-DAMP (M3) on ACh-evoked release were examined. The ordering of antagonist potency was: 4-DAMP (ED50 = 14 nM) > pirenzepine (3.8 microM) > methoctramine (> 10 microM). The results suggest that the muscarinic receptor mediating tracheal CGRP release resembles the M3 receptor subtype.
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Department of Anesthesiology, University of California, San Diego, La Jolla 92093-0818.
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D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology; D003959:Diamines / Q000494:pharmacology; D018738:Hexamethonium / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D018727:Muscarinic Antagonists; D010890:Pirenzepine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000378:metabolism; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D003959:Diamines; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D018738:Hexamethonium; D010890:Pirenzepine; D015740:Calcitonin Gene-Related Peptide; D000109:Acetylcholine; C054938:methoctramine; D002211:Capsaicin