The putative 5-HT1 receptor agonist, RU 24969, inhibits the efflux of 5-hydroxytryptamine from rat frontal cortex slices by stimulation of the 5-HT autoreceptor

The putative central 5-HT receptor agonist, 5-methoxy-3(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole succinate (RU 24969), was found to be a potent inhibitor of the continuous K+ evoked efflux of [3H]5-HT from superfused rat frontal cortex slices (pD2 7.45). The effects of RU 24969 were attenuated by the putative 5-HT autoreceptor antagonists, methiothepin, quipazine and (-)-propranolol but not by the alpha 2-adrenoceptor antagonist, idazoxan. It is concluded that RU 24969 inhibits K+ evoked efflux of [3H]5-HT from rat frontal cortex slices by stimulation of the 5-HT autoreceptor. Moreover, since RU 24969 potently displaced ligand binding to the 5-HT1 and 5-HT1B recognition sites but was only weakly active at the 5-HT2 receptor, the results lend support to the claim for a pharmacological resemblance between the 5-HT autoreceptor and the 5-HT1 recognition site and in particular the low affinity 5-HT1B subtype.