Central 5-hydroxytryptamine (5-HT) receptors in blood pressure regulation

Both intravenous and central administration of ketanserin, a 5-HT2 receptor antagonist, decrease blood pressure and sympathetic nerve activity, suggesting a central origin of its effects. However, ketanserin also possesses alpha 1-adrenoceptor blocking properties. Selective 5-HT2 receptor antagonists devoid of alpha 1-adrenoceptor blocking properties, e.g. LY 53857 and cinanserin, fail to reduce blood pressure and sympathetic nerve activity. In addition, 5-HT2 receptor agonists increase blood pressure and sympathetic nerve discharge. Therefore, it seems improbable that blockade of central 5-HT2 receptors alone could lead to a reduction in blood pressure. In contrast, the selective 5-HT1A receptor agonists 8-OH-DPAT and flesinoxan decrease blood pressure and heart rate by a centrally-mediated decrease in sympathetic tone and an increase in vagal tone. The sympatho-inhibitory effects of 5-HT1A receptor agonists result from the stimulation of postsynaptic 5-HT1A receptors within the ventrolateral pressor area. These results suggest that selective 5-HT1A receptor agonists acting in the central nervous system could be developed for the treatment of hypertension. Indeed, drugs such as flesinoxan and urapidil are effective in this setting.