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Effects of sympathetic stimulation and applied catecholamines on mechanical and electrical responses to stimulation of the vagus nerve in guinea‐pig isolated trachea
Author(s) -
McCaig Dorothy J.
Publication year - 1987
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 - 10.1111/j.1476-5381.1987.tb10293.x
Subject(s) - trachealis muscle , stimulation , vagus nerve , phentolamine , medicine , depolarization , hyperpolarization (physics) , isoprenaline , endocrinology , vagotomy , propranolol , acetylcholine , chemistry , potassium channel , charybdotoxin , organic chemistry , nuclear magnetic resonance spectroscopy
1 Mechanical and electrical responses to stimulation of the vagus nerve were studied in the isolated, innervated trachea of the guinea‐pig. 2 In approximately half the preparations tested, the amplitudes of mechanical constrictor responses to stimulation of the vagus were reduced substantially during a period of sympathetic stimulation. Vagal responses were unaltered in the remainder. 3 In single trachealis cells, stimulation of the vagus nerve or sympathetic stellate ganglion elicited depolarization and hyperpolarization, respectively. Vagally‐mediated depolarization was decreased, unchanged or increased in amplitude after a period of sympathetic stimulation. 4 Isoprenaline almost abolished mechanical responses induced by stimulation of the vagus, and this effect was blocked by propranolol. 5 Noradrenaline attenuated markedly vagal mechanical responses also, and this effect was blocked by a combination of propranolol and phentolamine. 6 Both noradrenaline and isoprenaline hyperpolarized single trachealis cells and greatly reduced the amplitude of vagally‐mediated depolarization. 7 Neither sympathetic stimulation nor applied catecholamines altered mechanical responses to applied acetylcholine, strongly suggesting that their effects on vagal responses are predominantly presynaptic.