INFLUENCE OF 5-HT1B 1D RECEPTORS ON DOPAMINE RELEASE IN THE GUINEA-PIG NUCLEUS-ACCUMBENS - A MICRODIALYSIS STUDY/

To clarify whether serotonin (5-HT) 5HT(1B/1D) receptors are involved in dopamine (DA) release, extracellular levels of DA were monitored by in vivo microdialysis during various conditions. 5-HT (10 mu M) alone , and together with the 5-HT1B/1D receptor antagonist, GR127935 (10 mu M), or the 5-HT1B/1D agonist, sumatriptan (1 mu M), were perfused int o the nucleus accumbens of freely moving guinea pigs. A 10-fold increa se in the extracellular concentration of DA was obtained during admini stration of 5-HT alone. The 5-HT-induced DA elevation was not signific antly affected by co-administration of sumatriptan (MANOVA; P > 0.05) but markedly attenuated by co-perfusion of GR127935 (MANOVA; P = 0.02) . Neither GR127935 nor sumatriptan, when administered alone, significa ntly affected extracellular DA levels. These results suggest that, in the DA-rich nucleus accumbens, 5-HT1B/1D receptors are not involved in the modulation of DA release during normal tonic or basal conditions but may take part in the regulation of DA release when synaptic 5-HT l evels are very high. (C) 1997 Elsevier Science Ireland Ltd.