POTENTIAL ANTIDEPRESSANT PROPERTIES OF SR 57746A, A NOVEL COMPOUND WITH SELECTIVITY AND HIGH-AFFINITY FOR 5-HT1A RECEPTORS

SR 57746A, (3-trifluoromethylphenyl)-N-[2-(naphth-2-yl)ethyl] was stud ied for its specific 5-HT1A receptor agonist action and antidepressant -like effects in the rat. The compound showed a high affinity for 5-HT 1A specific binding sites in the rat hippocampus (IC50 3 nM), moderate affinity (10(-7)-10(-6) M) for dopamine D-2 receptor, 5-HT uptake, 5- HT2, and alpha(1)-adrenoceptor binding sites and practically no effect on binding sites of monoamine, GABA(A), benzodiazepine and histamine receptors. It inhibited forskolin-stimulated adenylate cyclase activit y in rat hippocampal membranes at concentrations of 10(-6) and 10(-5) M. The effect of 10(-6) M SR 57746A on forskolin-stimulated adenylate cyclase activity was completely antagonized by 10(-6) M (-)-propranolo l. Administered per os as a three-dose course to rats, SR 57746A signi ficantly increased struggling in the forced swimming test at doses fro m 0.3 to 3 mg/kg. Single doses had no such effect. The effect of a thr ee-dose course with 1 mg/kg SR 57746A on rats' struggling was antagoni zed by pretreatment with 5 mg/kg i.p. metergoline, a non-selective 5-H T receptor antagonist, and by 20 mg/kg i.p. (-)-propranolol, an antago nist at 5-HT1 receptors. Three oral doses of 100 mg/kg parachloropheny lalanine, an inhibitor of 5-HT synthesis, and 100 mg/kg i.p. (+/-)-sul piride, an antagonist at dopamine D-2 receptors, also antagonized the effect of SR 57746A in the forced swimming test. The results show that SR 57746A has selectivity and high affinity for 5-HT1A receptors. The compound is a full agonist at this receptor and shows an antidepressa nt-like effect in the forced swimming test by a mechanism which seems to involve presynaptic 5-HT1A receptors and a permissive role of brain dopamine D-2 receptors.