CYCLIC-GMP INHIBITS PHOSPHOINOSITIDE TURNOVER IN CHOROID-PLEXUS - EVIDENCE FOR INTERACTIONS BETWEEN 2ND MESSENGERS CONCURRENTLY TRIGGERED BY 5-HT2C RECEPTORS

The present study examined the effects of the nitric oxide generator s odium nitroprusside (SNP), a membrane-permeable cGMP analog (dibutyryl -cGMP) and low calcium buffer incubation on choroid plexus serotonin 5 -HT2C receptor-mediated inositol monophosphate (IP) production. SNP (1 00 mu M) substantially inhibited 10(-6) M serotonin-stimulated IP prod uction (-46%, P < 0.02). Serotonin-stimulated IP production was increa sed in low calcium buffer (+280%, P < 0.01) in which serotonin-stimula ted cGMP formation is attenuated. Addition of dibutyryl-cGMP (500 mu M ) inhibited IP formation in low calcium buffer. The present data are s uggestive of an inhibitory effect of cGMP on IP formation in choroid p lexus, and raise the intriguing possibility of interactions between se cond messenger systems concurrently activated by 5-HT2C receptors.