ANXIOLYTIC EFFECT OF THE 5-HT1A COMPOUNDS 8-HYDROXY-2-(DI-N-PROPYLAMINO) TETRALIN AND IPSAPIRONE IN THE SOCIAL-INTERACTION PARADIGM - EVIDENCE OF A PRESYNAPTIC ACTION

This study analyses at which site, pre- or postsynaptic, the 5-HT(1)A ligands-8-hydroxy-2-(di-n-propylamina) tetralin (8-OH-DPAT) and ipsapi rone-induce their anxiolytic action, The experimental anxiety was asse ssed in the social interaction test An anxiolytic action was observed after the systemic administration of 8-OH-DPAT (0.25 and 0.5 mg/kg) an d ipsapirone (5 but not 10 mg/ kg), In 5,7-dihydroxybyptamine (5,7-DHT , 150 mu g/10 mu l) lesioned rats Be anxiolytic effect of 8-OH-DPAT an d ipsapirone was not observed, suggesting a presynaptic action of thes e drugs. When directly injected into the dorsal raphe nucleus 8-OH-DPA T (0.1 mu g/mu l) and ipsapirone (0.2 mu g/mu l) both compounds produc e anxiolytic effects, At same doses, these drugs lacked an effect afte r their intrahippocampal infusion, All data strongly suggest that both drugs act presynaptically to reduce the anxiety levels in the social interaction paradigm.