Serotonin-1C sites in the choroid plexus are not linked in a stimulatory or inhibitory way to adenylate cyclase.

The association of the serotonin recognition sites in the pig choroid plexus (5-HT-1C sites) with an adenylate cyclase was examined. The interaction of serotonin and mianserin with [3H]mesulergine binding was not affected by the stable GTP analogue GppNHp. The binding of [3H]serotonin to choroid plexus membranes was also unaffected by GppNHp while a dose-dependent decrease was observed in pig cortical and hippocampal membranes. The porcine choroid plexus contained a forskolin- and histamine-sensitive adenylate cyclase. Serotonin, however, was ineffective in this preparation. While forskolin-stimulated adenylate cyclase in the rat hippocampus was inhibited by serotonin forskolin-stimulated adenylate cyclase in the choroid plexus was insensitive to serotonin. These results indicate that the serotonin recognition sites in the choroid plexus are not linked in a stimulatory or inhibitory way to an adenylate cyclase, in contrast with other 5-HT-1 receptor subtypes.