BIOCHEMICAL AND ELECTROPHYSIOLOGICAL PROPERTIES OF SR 57746A, A NEW, POTENT 5-HT(1A) RECEPTOR AGONIST

SR 57746A (1-[2-(naphth-2-yl) ethyl]-4-(3-trifluoromethylphenyl)-1, 2, 5, 6 tetra-hydropyridine hydrochloride) binds competitively, and with high affinity (K(i) = 2.0 +/- 0.7 nM) to 5-HT1A receptors from mt hip pocampus in vitro, but has much less affinity for other 5-HT receptor subtypes (IC50 > 650 nM). SR 57746A produces a concentration-dependent inhibition of forskolin-stimulated adenylate cyclase activity in rat hippocampal homogenates, with a maximal effect identical to that of 8- OH-DPAT, suggesting that SR 57746A behaves as a full agonist in this e xperimental model. SR 57746A potently displaces [H-3]8-OH-DPAT binding to rat hippocampal pal membranes ex vivo, with an ID50 of 11.1 mg/kg po, 30 min after administration, and 2.8 mg/kg po, 2 h after administr ation. This effect of SR 57746A is long-lasting (at least 24 hours at 10 mg/kg po). SR 57746A does not modify the levels of 5-HT or DA in va rious brain areas, but decreases the concentrations of 5-HIAA, and inc reases those of DOPAC, HVA and 3-MT. Following iv administration, SR 5 7746A (0.095 to 0.25 mg/kg) inhibits the spontaneous firing of dorsal raphe neurones, but does not modify the activity of DA neurones rones in the substantia nigra or ventral tegmental area. Thus, SR 57746A is a potent, selective and full agonist at 5-HT1A receptors in vitro and vivo.