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5‐Hydroxytryptamine is a possible neurotransmitter of the non‐cholinergic excitatory nerves in the longitudinal muscle of rainbow trout stomach ( Salmo gairdneri )
Author(s) -
Kitazawa Takio
Publication year - 1989
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.1476-5381.1989.tb14606.x
Subject(s) - hexamethonium , methysergide , endocrinology , medicine , atropine , acetylcholine , tetrodotoxin , excitatory postsynaptic potential , phentolamine , stimulation , cholinergic , chemistry , biology , serotonin , inhibitory postsynaptic potential , receptor
1 The neurotransmitter of the non‐cholinergic excitatory nerves in the rainbow trout stomach was identified on the basis of the pharmacological properties of the contractile responses to transmural stimulation (TMS) and nicotine. 2 TMS caused tetrodotoxin‐sensitive contractions of rainbow trout stomach strips in a frequency‐dependent manner (0.5–50 Hz). Atropine (1 μ m ) significantly decreased the contractile response to low‐frequency stimulation (0.5–2 Hz), but did not affect that to high‐frequency stimulation (3–20 Hz). 3 The atropine‐resistant contractile response to TMS (20 Hz) was unaffected by hexamethonium (100 μ m ), phentolamine (5.4 μ m ), pyrilamine (1 μ m ), naloxone (1 μ m ) or substance P‐induced desensitization. 4 5‐Hydroxytryptamine (5‐HT, 3 n m ‐3 μ m ) caused atropine‐resistant contractions in a concentration‐dependent manner. In the presence of atropine, methysergide (1 μ m ) decreased the contractile responses to TMS and 5‐HT. 5 Nicotine (3 μ m ‐500 μ m ) induced atropine‐resistant contractions that were completely abolished by tetrodotoxin or hexamethonium. Also methysergide inhibited the contractile responses to nicotine. 6 An acid extract of rainbow trout stomach exhibited atropine‐resistant contractions that were decreased by methysergide, in both rainbow trout stomach and guinea‐pig ileum longitudinal smooth muscle preparations. 7 The present results indicate that, in longitudinal muscle strips of the rainbow trout stomach, 5‐HT is one of the mediators (neurotransmitters) of the non‐cholinergic excitatory contractions induced by TMS and nicotine.