Pharmacology of the 5-hydroxytryptamine-induced depolarization of the ferret vagus nerve in vitro

Grease-gap recordings revealed that 5-hydroxytryptamine (5-HT) depolarized the ferret vagus nerve (pEC50 = 4.9). This response was mimicked by 2-methyl-5-HT and 1-phenylbiguanide, but not by 5-carboxamidotryptamine. Paroxetine (1 microM) or ketamine (10 microM) did not potentiate the response. Ketanserin (1 microM) did not reduce the depolarization, but four 5-HT3 receptor antagonists did. It is concluded that 5-HT depolarizes the ferret vagus nerve via 5-HT3 receptors, but these receptors may differ pharmacologically from those in other species.