Differential distribution of ionic channels and muscarinic receptors at the cat tracheal neuromuscular junction

Citation
K. Tanaka et al., Differential distribution of ionic channels and muscarinic receptors at the cat tracheal neuromuscular junction, AUTON NEURO, 84(1-2), 2000, pp. 30-39
Citations number
23
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences & Behavoir
Journal title
AUTONOMIC NEUROSCIENCE-BASIC & CLINICAL
ISSN journal
1566-0702 → ACNP
Volume
84
Issue
1-2
Year of publication
2000
Pages
30 - 39
Database
ISI
SICI code
1566-0702(20001030)84:1-2<30:DDOICA>2.0.ZU;2-#
Abstract
The ionic and pharmacological properties of atropine-sensitive excitatory j unction potentials (EJPs) were investigated by the double sucrose gap and m icroelectrode membrane potential recording methods, and compared with those of inward currents evoked by carbachol (I-CCh), in cat tracheal smooth mus cle. A single and repetitive field stimulation (10-30 V, 50 mu s, 20 Hz) ev oked atropine-inhibitable EJPs and associated twitch-like contractions. Red uction in external Nai concentration strongly, but in the external Cl- conc entration, decreased the EJP amplitude after 5 min super-fusion, although p rolonged exposure to low Cl- solutions attenuated the EJPs modestly. Chlori de channel blockers such as 9-AC and niflumic acid (each 100 mu M), at conc entrations high enough to inhibit I-CCh almost completely, failed to abolis h the EJPs. Pirenzepine, AF-DX116 and 4-DAMP all effectively inhibited the EJPs at their concentrations to block respective muscarinic receptor subtyp es relatively specifically, while depletion of internal stores by 10 mM caf feine and/or 3 mu M ryanodine caused only a partial decrease in the EJP amp litude. These properties are considerably different from those of I-CCh whi ch is activated exclusively through activation of the M-3 receptor/IP3-medi ated Ca2+ release pathway and reflects mostly a Ca2+ -dependent Cl- current , and suggests the differential distribution of muscarinic receptors and io nic channels inside and outside of the cholinergic neuromuscular junction o f this muscle. (C) 2000 Elsevier Science B.V. All rights reserved.