PHARMACOLOGICAL CHARACTERIZATION OF [S-35] GTP-GAMMA-S BINDING TO CHINESE-HAMSTER OVARY CELL-MEMBRANES STABLY EXPRESSING CLONED HUMAN 5-HT1D RECEPTOR SUBTYPES

[S-35]-GTP gamma S binding has been used to study the function of cloned human 5-HT1D receptor subtypes stably expressed in chinese hamster ovary (CHO) cells. 5-HT stimulated [S-35]-GTP gamma S binding to membranes from cells expressing 5-HT1D alpha or 5-HT1D beta receptors. In membranes containing 5-HT1D beta receptors, 5-CT and sumatriptan stimulated binding to a similar extent as 5-HT while yohimbine, metergoline and 8-OHDPAT were partial agonists. The order of potency for agonists was 5-CT > 5-HT > metergoline > sumatriptan > yohimbine > 8-OHDPAT. The stimulation of binding by 5-HT in membranes containing 5-HT1D beta receptors was potently antagonised by methiothepin (pA(2) 8.9 +/- 0.1). The overall pharmacological profile for the human 5-HT1D beta receptor, defined using [S-35]-GTP gamma S binding, agreed well with that reported for inhibition of forskolin-stimulated adenylyl cyclase. In addition, methiothepin and ketanserin inhibited basal [S-35]-GTP gamma S binding to membranes containing 5-HT1D alpha or 5-HT1D beta receptors, suggesting that these compounds show negative efficacy at 5-HT1D receptor subtypes. The data show that [S-35]-GTP gamma S binding is a suitable method for studying the interaction between cloned human 5-HT1D receptors and G-proteins.