Regional haemodynamic effects of urocortin in the anaesthetized rat

Urocortin is an endogenous vasodilator peptide that is related to corticotrophin-releasing factor. We examined the haemodynamic effects of urocortin in thiobutabarbital-anaesthetized rats, via the triple-isotope microspheres technique. Urocortin (3 nmol/kg, i.v. bolus) reduced mean arterial pressure (- 25 mm Hg) through a decrease in total peripheral resistance (- 43%). This was associated with an increase in cardiac output (+ 24%) and vasodilatation of the following tissues: heart and stomach ( approximate to 300% of baseline); liver, intestine, caecum/colon, skeletal muscle and skin ( approximate to 200%); and testes ( approximate to 150%). Arterial conductances of the kidneys, spleen and brain were unaffected by urocortin. Neither the vehicle (0.9% NaCl) nor a low dose of urocortin (0.3 nmol/kg) altered any measurements. Therefore, urocortin causes generalized vasodilatation as follows: heart and stomach>liver, intestine, caecurn/colon, skeletal muscle and skin>testes. (C) 2003 Elsevier Science B.V. All rights reserved.