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Mediation by 5‐HT 3 receptors of an excitatory effect of 5‐HT on dorsal vagal preganglionic neurones in anaesthetized rats: an ionophoretic study
Author(s) -
Wang Yun,
Ramage Andrew G.,
Jordan David
Publication year - 1996
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.1476-5381.1996.tb15594.x
Subject(s) - tropisetron , agonist , chemistry , granisetron , 5 ht3 receptor , excitatory postsynaptic potential , receptor antagonist , ppads , 5 ht receptor , receptor , medicine , endocrinology , serotonin , antagonist , antiemetic , vomiting
1 . Extracellular recordings were made from 141 vagal preganglionic neurones in the dorsal vagal nucleus (DVN). The effects of ionophoretic administration of 5‐hydroxytryptamine (5‐HT), the 5‐HT 3 receptor agonist, phenylbiguanide (PBG) and the antagonists, granisetron and tropisetron (ICS 205–930) on these vagal preganglionic neurones were studied in pentobarbitone sodium anaesthetized rats. 2 . Ionophoretic application of 5‐HT at low currents (< 10 nA) increased the activity in 46 (73%) of 63 neurones tested. Application of granisetron (5–20 nA) or tropisetron (5–20 nA) abolished or attenuated the 5‐HT excitatory responses in 8 out of 11 and 5 out of 5 neurones respectively. At the currents used, neither antagonist had any effect on baseline firing rate. 3 . Ionophoresis of the selective 5‐HT 3 receptor agonist, phenylbiguanide (0–40 nA) excited 54 (82%) of the 66 vagal neurones tested, whilst the remaining 12 neurones were unaffected. 4 . Granisetron applied either ionophoretically (8/11) or intravenously (3/3), abolished or attenuated the excitations evoked by PBG. Similarly, tropisetron administered either ionophoretically (2/3) or intravenously (2/2), attenuated the PBG excitation. In contrast, the PBG excitations were unaffected by the 5‐HT 2 receptor antagonist, cinanserin (2/2), and the selective 5‐HT 1A receptor antagonist, WAY‐100802 (6/6). 5 . In conclusion, excitation of vagal preganglionic neurones evoked by ionophoretic application of 5‐HT is mediated in part by 5‐HT 3 receptors and activation of 5‐HT 3 receptors on and/or in the vicinity of vagal motoneurones causes excitation of these neurones.