THE 5-HT1A RECEPTOR ANTAGONIST (S)-UH-301 BLOCKS THE (R)-8-OH-DPAT-INDUCED INHIBITION OF SEROTONERGIC DORSAL RAPHE CELL FIRING IN THE RAT

(S)-UH-301 [(S)-5-fluoro-8-hydroxy-2-(dipropylamino) 0.5-4.0 mg/kg i.v .] did not significantly alter the firing rate of 5-hydroxytryptamine (5-HT) containing neurons in the dorsal raphe nucleus (DRN) as a group , although some individual cells were activated whereas others were de pressed. However, (S)-UH-301 (2.0 mg/kg i.v.) consistently reversed th e inhibition of DRN-5-HT cells produced by the selective 5-HT1A recept or agonist (R)-8-OH-DPAT (0.5 mu g/kg i.v.) and the dose-response curv e for this effect of (R)-8-OH-DPAT was markedly shifted to the right b y pretreatment with (S)-UH-301 (1.0 mg/kg i.v.). These results support the notion that (S)-UH-301 acts as an antagonist at central 5-HT1A re ceptors.