The 5-HT1A receptor agonist, 8-OH-DPAT ((+/-)-8-dihydroxy-2-(di-n-propylamino) tetralin), (0.63 mg/kg, s.c.) elicited spontaneous tail-flicks (STFs) in rats. This response was potentiated by the selective 5-HT2C receptor agonist, RO 60-0175 ((S)-2-(6-chloro-5-fluoroindol-1-yl)-1-methylethylamine) fumarate) (0.16 mg/kg, s.c.), the action of which was abolished by the novel 5-HT2C antagonist, SB 206,553 (5 methyl-1-(3-pyridil-carbamoyl)-1,2,3,5-tetrahydropyrrolo[2,3 -f]indole) (0.16 mg/kg, s.c.). These data show that 5-HT1A receptor-mediated STFs in rats are facilitated by activation of 5-HT2C receptors supporting the existence of functional interactions between these sites.