[Peripheral and central participation in hemodynamic effects of serotonin2 receptor stimulation]

The systemic and regional haemodynamic effects of DOI were investigated in the anaesthetized rat. DOI (1-300 micrograms/kg i.v.) increased mean arterial pressure (MAP), total peripheral resistance (TPR) and all regional vascular resistances studied (hindquarters, mesenteric and renal). DOI was more effective on renal vascular bed. Cardiac output (CO) and heart rate (HR) did not change. The effects of DOI were antagonized by LY 53857 (10 micrograms/kg i.v.) and spiperone (10 or 100 micrograms/kg i.v.), selective 5-HT2 receptor antagonists. Intracerebroventricular administration of DOI (100 micrograms/kg) increased MAP, TPR, regional vascular resistances and did not change HR and CO. Pretreatment with xylamidine (10 micrograms/kg i.v.), a selective peripheral 5-HT2 receptor antagonist, blocked i.v. and i.c.v. effects of DOI. These results suggest that: 1) the increase in MAP induced by the stimulation of 5-HT2 receptors is due to an increase in TPR. All regional vascular resistances participate in the increase of TPR. 2) Peripheral and central 5-HT2 receptors seem to be implicated in the control of regional vascular resistances.