5-HT(1B) antagonists modulate clearance of extracellular serotonin in rat hippocampus

In vivo chronoamperometry was used to determine the effects of locally applied antagonists of the serotonin-1B (5-HT(1B)) receptor (cyanopindolol, 5-HT-moduline and methiothepin) on the clearance of 5-HT in the CA3 region of the dorsal hippocampus and the corpus callosum (a brain region devoid of serotonin transporters and 5-HT(1B) receptors) of the rat. When 5-HT was pressure ejected into these regions, reproducible signals were detected. In the CA3 region, local application of 5-HT(1B) antagonists decreased the rate of clearance of the serotonin signal comparably to the selective 5-HT uptake inhibitor (SSRI), fluvoxamine. By contrast, in the corpus callosum, none of the drugs altered the 5-HT signal. One interpretation of these data is that 5-HT(1B) receptors can modulate the activity of the 5-HT transporter.