5-hydroxytryptamine and cardiovascular regulation.

All 5-hydroxytryptamine (5-HT; serotonin) receptors, except the 5-HT6 type, have been shown to be involved in cardiovascular regulation. In the periphery, 5-HT is stored in platelets, but the physiological role of 5-HT in the regulation of vascular tone (as opposed to its role in coagulation) remains unclear. However, central 5-HT1A, 5-HT3 and 5-HT7 receptors do play a physiological part in the regulation of cardiovascular reflexes, controlling changes in parasympathetic (vagal) drive to the heart. These reflexes also affect activity in the sympathetic nervous system, which itself can be inhibited by central 5-HT(1A) receptors to cause falls in blood pressure and excited by 5-HT2 receptors to cause rises in blood pressure. The physiological role of these receptors in the central regulation of the sympathetic nervous system is unclear, although 5-HT2 receptors could be involved in the development of deoxycorticosterone-acetate-salt hypertension, which is probably related to their role in the control of vasopressin release.