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Interactions between acetylcholine, 5‐hydroxytryptamine, nicotine and morphine on isolated rabbit atria
Author(s) -
CHITTAL S. M.,
DADKAR N. K.,
AITONDÉ B. B.
Publication year - 1968
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.1476-5381.1968.tb07945.x
Subject(s) - acetylcholine , chemistry , nicotine , physostigmine , bretylium , morphine , atropine , cholinergic , pharmacology , medicine , endocrinology , stimulation , nicotinic agonist , hexamethonium , receptor , adrenergic , biochemistry
1 The effects of 5‐hydroxytryptamine (5‐HT) and morphine on the responses to acetylcholine and nicotine of isolated rabbit atria were studied. 2 5‐Hydroxytryptamine (10 μg/ml.) and morphine (20 μg/ml.) blocked the negative chronotropic and inotropic actions of acetylcholine. 3 Nicotine (20 μg/ml.) produced stimulation of the atria, which was blocked by dichlorisoprenaline, morphine, 5‐HT, bretylium and hemicholinium. Hemicholinium block was reversed by choline. 4 In reserpinized preparations, nicotine produced inhibition of atria and this action was also blocked by atropine, 5‐HT and morphine. Inhibition induced by nicotine was potentiated by physostigmine. 5 5‐Hydroxytryptamine (20 μg/ml.) produced stimulation of atria. This was blocked by bretylium and reduced by hemicholinium. Hemicholinium block was reversed by choline. 6 It is concluded that 5‐HT in low concentrations acts as a weak agonist at the cholinoceptive receptors and therefore blocks the action of acetylcholine. Furthermore, nicotine and larger doses of 5‐HT have actions on ganglionic structures and liberate acetylcholine, which in turn releases catecholamines.