Effect of serotonin on intracellular free calcium of rat cerebrovascular smooth muscle cells in culture.

Smooth muscle cells were dissociated from conducting cerebral arteries of adult rats and maintained in culture for 2-4 days. The calcium-sensitive fluorescent probe, fura-2, was used to study the effect of the vasoconstrictor serotonin (5-HT) on the level of free intracellular Ca2+ in these cells. The baseline level of free intracellular calcium was 39 +/- 3.6 nM. In 74 out of 110 cells, 5-HT application transiently increased the free Ca2+ content. This effect was dose-dependent and was suppressed by nanomolar concentrations of the 5-HT2 receptor antagonist, ketanserin. The 5-HT induced rise in free intracellular calcium was not prevented by the presence of Co2+, La3+, or nifedipine, blockers of voltage-sensitive calcium channels. These results indicate that 5-HT mobilizes intracellular Ca2+ in cultured smooth muscle cells derived from the rat cerebrovasculature. The mobilization of intracellular Ca2+ appears to be triggered by a 5-HT2 type receptor, although further pharmacological experiments are required to verify this hypothesis.