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Evidence that the 5‐HT 3 receptors of the rat, mouse and guinea‐pig superior cervical ganglion may be different
Author(s) -
Newberry Nigel R.,
Cheshire Sarah H.,
Gilbert Michael J.
Publication year - 1991
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.1476-5381.1991.tb12221.x
Subject(s) - ketanserin , superior cervical ganglion , guinea pig , agonist , spiperone , receptor , medicine , endocrinology , 5 ht receptor , depolarization , biology , ganglion , serotonin , chemistry , anatomy
1 Using grease‐gap recordings from the isolated superior cervical ganglion of mouse, rat and guinea‐pig, we have compared the depolarization evoked by 5‐hydroxytryptamine (5‐HT) with that evoked by the selective 5‐HT 3 receptor agonist 2‐methyl‐5‐HT (2‐Me‐5‐HT). 2 The maximum depolarization induced by 2‐Me‐5‐HT was smaller than that induced by 5‐HT in all three species, and particularly in the guinea‐pig. 3 The 5‐HT 2 receptor antagonist ketanserin (1 μ m ) caused a clear rightward shift of the dose‐response curve to 5‐HT on the guinea‐pig ganglion, but not on the mouse or rat ganglion. Spiperone (0.03 μ m ) had a quantitatively similar action to ketanserin (0.1 μ m ) on the 5‐HT dose‐response curve of the guinea‐pig ganglion. Ketanserin had no significant effect on the dose‐response curve to 2‐Me‐5‐HT on any of these ganglia. 4 Using 2‐Me‐5‐HT as the agonist, we determined the pA 2 values for two 5‐HT 3 receptor antagonists. The potency of ICS 205–930 varied by approximately 100 fold between the species and that of (+)‐tubocurarine varied by over 1000 fold. The differences in the pA 2 values of these compounds varied independently among the species. 5 We conclude that 5‐HT 3 receptors are present on the superior cervical ganglion from the rat, mouse and guinea‐pig, but these receptors may be pharmacologically distinct from each other. In addition, the depolarization of the guinea‐pig superior cervical ganglion by low concentrations of 5‐HT is largely mediated by ketanserin‐sensitive receptors.