Effect of 5-hydroxytryptamine on glossopharyngeal afferent nerve activity in anesthetized rats.
Excitatory responses to 5-hydroxytryptamine (5-HT) were recorded from the whole glossopharyngeal afferent nerve in anesthetized rats, using an electrophysiological technique. Bolus intravenous injection of 5-HT (6.25-50 micrograms/kg) evoked a dose-dependent excitation of glossopharyngeal afferent nerve activity with a rapid onset and lasting a few seconds. This response was blocked by a selective 5-HT3 receptor antagonist, YM060 (10 micrograms/kg i.v.). A 5-HT3 receptor agonist, 2-methyl-5-HT (6.25-50 micrograms/kg), also produced a rapid and dose-dependent excitation of this nerve activity, and YM060 (10 micrograms/kg i.v.) caused an inhibition of this effect. In contrast, efferent glossopharyngeal nerve activity was not altered by 5-HT even at a high dose (50 micrograms/kg). These results suggest that exogenous 5-HT may elicit excitation of the glossopharyngeal afferent nerve, and that this effect might be mediated via the 5-HT3 receptors on the nerve endings.
Yoshioka
M
M
First Department of Pharmacology, Hokkaido University School of Medicine, Sapporo, Japan.
Ikeda
T
T
Togashi
H
H
Saito
H
H
D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D004594:Electrophysiology; D005930:Glossopharyngeal Nerve / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology*; D012702:Serotonin Antagonists
D001562:Benzimidazoles; D012702:Serotonin Antagonists; D012701:Serotonin; C045918:2-methyl-5-HT; C071315:ramosetron