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Pharmacological characterization of 5‐hydroxytryptamine‐induced excitation of afferent cervical vagus nerve in anaesthetized rats
Author(s) -
Yoshioka Mitsuhiro,
Ikeda Toshiya,
Abe Masayuki,
Togashi Hiroko,
Minami Masaru,
Saito Hideya
Publication year - 1992
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.1476-5381.1992.tb14372.x
Subject(s) - ketanserin , vagus nerve , agonist , excitatory postsynaptic potential , receptor antagonist , endocrinology , chemistry , medicine , 5 ht receptor , receptor , antagonist , pharmacology , serotonin , stimulation
1 An excitatory response to 5‐hydroxytryptamine (5‐HT) was measured from the afferent vagus nerve of anaesthetized rats. Measurements were determined by an extracellular recording from the whole nerve. 2 Intravenous bolus injection of 5‐HT (1.56–100 μg kg −1 ) evoked a dose‐dependent excitation of afferent vagus nerve activity. This response was blocked not only by a selective 5‐HT 3 receptor antagonist, GR38032F (10 and 100 μg kg −1 ), but also by a 5‐HT 2 receptor antagonist, ketanserin (10 and 100 μg kg −1 ). 3 Both a 5‐HT 3 receptor agonist, 2‐methyl‐5‐HT (3.12–100 μg kg −1 ), and a 5‐HT 2 receptor agonist, α‐methyl‐5‐HT (3.12–50 μg kg −1 ), produced a dose‐dependent excitation of afferent vagus nerve activity. These excitatory effects were antagonized by GR38032F (10 μg kg −1 ) and ketanserin (10 μg kg −1 ), respectively. 4 A 5‐HT 1 like receptor agonist, 5‐carboxamidotryptamine (50 μg kg −1 ), and a putative 5‐HT 4 receptor agonist, 5‐methoxytryptamine (100 μg kg −1 ), failed to produce excitatory effects on the afferent vagus nerve. 5 These results suggest that the 5‐HT‐induced excitatory response of the afferent vagus nerve might be mediated not only via 5‐HT 3 receptors but also via 5‐HT 2 receptors in anaesthetized rats. It is unlikely, however, that either 5‐HT 1 ‐like or putative 5‐HT 4 receptors are involved in the excitatory response of the afferent vagus nerve to 5‐HT.