Cloning of serotonin 5-HT1 receptor subtypes from the chimpanzee, gorilla and Rhesus monkey and their agonist-induced guanosine 5′γS triphosphate binding

5-HT₁ receptor subtypes (_1B, _1D and _1F) have been implicated in migraine pathophysiology and their ligands have been examined for pharmacological actions in various experimental animal models. Considerable divergences exist, however, in their primary sequences between experimental animals and human, and additional models closer to human, such as non-human primates seem to be useful for migraine research. Earlier, we cloned the 5-HT_1D, and here 5-HT_1B and 5-HT_1F receptors from the chimpanzee, gorilla and Rhesus monkey, via polymerase chain reactions with their genomic DNAs and primers designed from the corresponding human receptors. Direct sequencing of PCR products showed that the 5-HT_1B receptors from the chimpanzee, gorilla and monkey differ from the human receptor by 0, 1 and 7 residues, respectively while 5-HT_1F receptors differ by 0, 3 and 10 residues, respectively. These divergent residues are mostly conservatively substituted and also largely confined to the N-terminal region and the 3rd intracellular loop, away from transmembrane segments and intracellular loops near membrane which are critical for ligand binding and G protein coupling. The chimpanzee 5-HT_1D, 5-HT_1B and monkey 5-HT_1F receptors, as heterologously expressed in human embryonic kidney 293 cells, showed robust agonist-induced guanosine 5′gamma ³⁵S triphosphate (GTPγ³⁵S) binding through activation of G proteins containing Gγ_i subunits. Moreover, pronounced inhibition of basal GTPγ³⁵S binding by methiothepin (an antagonist), representing constitutively active receptors, was observed with only 5-HT_1D. Overall, ligand binding and GTPγ³⁵S binding profiles for these primate receptors are comparable to those for the human receptors and validate non-human primates as useful models for human migraine research.