The present study examined the effects of bicuculline on the mouse 5-hydroxytryptamine(3A) receptor (5-HT(3A) receptor and the human α2 subunit of the glycine receptor. Bicuculline antagonized both the 5-HT(3A) receptor (IC50=20.12±0.39 μM) and the α2 glycine receptor (IC50=169.40±1.73 μM). A competitive form of antagonism by bicuculline was suggested by experiments in which the EC50s for 5-HT and glycine were increased in the 5-HT(3A) and α2 glycine receptors, respectively, as bicuculline concentrations were increased. A competitive nature of antagonism by bicuculline at the 5-HT(3A) receptor was also suggested by displacement of the competitive antagonist, [3H]GR65630 in SF21 insect cells expressing the 5-HT(3A) receptor (K(i)=19.01±0.71 μ M). Our data and that of others reveal that bicuculline, a purported selective antagonist of the GABA(A) receptor, antagonizes at least one receptor subclass in every member of the superfamily of ligand-gated ion channels. Copyright (C) 2000 Elsevier Science B.V.
- 5-HT receptor
- 5-HT(5-hydroxytryptamine, serotonin)
- Nicotinic acetylcholine receptor
- glycine receptor