Pharmacological characterisation of a cloned dog 5-HT1B receptor cell line.

In this study, the binding of [3H]5-HT to the cloned dog 5-hydroxytryptamine1B (dog 5-HT1B) receptor, stably expressed in Chinese hamster ovary cells (ATCC CCL 61)(CHO-K1), was characterised and its pharmacology compared with that of the cloned human and rat 5-HT1B receptors. [3H]5-HT specifically labeled, with high affinity, an apparently homogeneous population of binding sites in the dog 5-HT1B receptor cell line yielding a pKd of 8.1. [3H]5-HT inhibition and agonist-induced [35S] guanosine 5'[gamma-thio] triphosphate ([35S]GTPgammaS) binding studies revealed comparable results with the human but not the rat 5-HT1B receptor. In all three recombinant receptor cell lines, methiothepin displayed inverse agonism and GR127935 (N-[4-methoxy-3-(4-methyl-1-piperizinyl)phenyl]-2'-methyl-4'-(5-me thyl-1,2,4-oxadiazole-3-yl)[1,1'-biphenyl]-carboxamide) weak partial agonism.