Serotonin increases the production of inositol phosphates and mobilises calcium via the 5-HT sub(2) receptor in A sub(7)r sub(5) smooth muscle cells

Serotonin (5-HT) induces inositol phosphate production and the efflux of super(45)Ca super(2+) in a smooth muscle cell line (A sub(7)r sub(5)) derived from rat aorta. The effects were pharmacologically characterised and compared to data obtained in radioligand binding studies performed with the 5-HT sub(2) ligand ( super(3)H)ketanserin in rat brain cortex membranes. 5-HT causes in increase in the levels of inositol trisphosphate (InsP sub(3)), inositol bisphosphate (InsP sub(2)) and inositol phosphate (InsP sub(1)). 5-HT stimulated the efflux of super(45)Ca super(2+) from preloaded cells. There was a very good correlation between antagonism of Ca super(2+) release and 5-HT sub(2) binding as measured using a series of 13 antagonists. The data suggests that 5-HT mobilises intracellular Ca super(2+) via the production of InsP sub(3) in this smooth muscle cell line, an effect mediated by a 5-HT sub(2) receptor.