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A physiologically-evoked M1-muscarinic depolarization in guinea-pig inferior mesenteric ganglion neurons.
- Source :
-
Journal of the autonomic nervous system [J Auton Nerv Syst] 1994 Mar; Vol. 46 (3), pp. 207-15. - Publication Year :
- 1994
-
Abstract
- The possibility of physiologically-evoked muscarinic excitatory synaptic potentials was examined in the inferior mesenteric ganglion (IMG) with intracellular microelectrodes in vitro. Three types of depolarizing responses were evoked concurrently by colonic distension: (1) fast nicotinic excitatory postsynaptic potentials (EPSPs); (2) an 'intermediate' time course depolarization and (3) a long time course potential that persisted throughout the period of distension. After hexamethonium was superfused over the ganglia the long time course potential was observed in 91% of IMG neurons. Intermediate time course of depolarizations were observed in 100% of IMG neurons and correlated with each propulsive contraction of the distal colon. The intermediate depolarizations had an average amplitude of 1.8 +/- 0.1 mV (n = 175 individual events; 27 preparations) with an average duration of 11.9 +/- 0.8 sec (n = 28 individual events). The intermediate time course synaptic potentials were accompanied by an increase in input resistance of 15% (n = 6). Superfusion of atropine (1 microM; n = 6) on the IMG or the M1-selective antagonist pirenzepine (1 microM; n = 5) abolished the intermediate time course synaptic potentials during distension. Superfusion of the M2-selective antagonist AF-DX 116 (1 microM; n = 4) had no effect. In all preparations examined, distension-induced intermediate time course depolarizations were blocked by tetrodotoxin (TTX) (3 microM). Pressure ejection of carbachol (1 mM, 60-100 ms pulses) evoked depolarizations of similar amplitude (6.5 +/- 0.7 mV; n = 18) and duration to the intermediate depolarizations observed during propulsive contractions.(ABSTRACT TRUNCATED AT 250 WORDS)
- Subjects :
- Action Potentials
Animals
Atropine pharmacology
Carbachol pharmacology
Female
Gastrointestinal Motility
Guinea Pigs
Hexamethonium
Hexamethonium Compounds pharmacology
Male
Pirenzepine analogs & derivatives
Pirenzepine pharmacology
Receptors, Muscarinic classification
Receptors, Muscarinic drug effects
Colon innervation
Ganglia, Sympathetic physiology
Mechanoreceptors physiology
Receptors, Muscarinic physiology
Stress, Mechanical
Subjects
Details
- Language :
- English
- ISSN :
- 0165-1838
- Volume :
- 46
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- Journal of the autonomic nervous system
- Publication Type :
- Academic Journal
- Accession number :
- 7912245
- Full Text :
- https://doi.org/10.1016/0165-1838(94)90038-8