Central cardiovascular action of urotensin II in conscious rats

Objective To examine the central cardiovascular action of urotensin II in conscious rats. Methods Intracerebroventricular (ICV) injections of urotensin II (1 and 10 nmol) were carried out in conscious Wistar rats. The effects of intravenous (i.v.) urotensin II (10 nmol) were also determined. Results The ICV injection of urotensin II at a dose of 1 nmol did not alter the arterial pressure or heart rate significantly, while 10 nmol urotensin II increased the arterial pressure and heart rate. The mean arterial pressure at 5 min of ICV urotensin II was 121 +/- 4 mmHg, which was significantly higher than that obtained by ICV injection of artificial cerebrospinal fluid (107 +/- 3 mmHg, P < 0.05). In addition, significant increases in heart rate were observed 5-15 min after ICV urotensin II. Pretreatment with pentolinium (5 mg/kg, i.v.) significantly attenuated the increases in mean arterial pressure (20 +/- 3 versus 8 +/- 2 mmHg, P < 0.01) and heart rate (78 +/- 18 versus 7 +/- 5 beats/min, P < 0.05) induced by ICV urotensin II. On the other hand, i.v. injection of urotensin II (10 nmol) elicited a depressor response associated with tachycardia; mean arterial pressure 5 min after injection was significantly lower in the urotensin II-injected rats (89 +/- 5 mmHg) than in the control rats (102 +/- 2 mmHg, P < 0.05), and the heart rate was significantly higher in the former (402 +/- 11 versus 360 +/- 9 beats/min, respectively, P < 0.05). Conclusions Central urotensin II produces pressor and tachycardic responses through sympathetic activation, while peripheral urotensin II exerts a vasodilation-mediated depressor response in conscious rats. (C) 2003 Lippincott Williams Wilkins.