Y1- and 1-receptor control of basal hindlimb vascular tone

Jackson, Dwayne N., Earl G. Noble, and J. Kevin Shoemaker. Y1and 1-receptor control of basal hindlimb vascular tone. Am J Physiol Regul Integr Comp Physiol 287: R228–R233, 2004. First published March 25, 2004; 10.1152/ajpregu.00723.2003.—The role of endogenous Y1-receptor activation on skeletal muscle vasculature under baseline conditions is currently debated and no in vivo studies have been performed to address this issue. Therefore, this study was designed to address the effect of Y1-receptor and/or 1-adrenoceptor antagonism on basal hindlimb vascular conductance in male SpragueDawley rats in vivo. Left hindlimb vascular conductance, carotid artery mean arterial pressure, and heart rate were measured during low volume infusion of N-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-D-arginine amide (BIBP3226; 100 g/kg), prazosin (20 g/kg), and combined blockade to the left hindlimb. Vascular conductance increased 1.5 0.5 l min 1 mmHg 1 with BIBP3226 infusion, 1.7 0.5 l min 1 mmHg 1 with prazosin infusion, and 4.8 1.0 l min 1 mmHg 1 with combined blockade (P 0.05). Interestingly, systolic vascular conductance increased in all three conditions, but diastolic vascular conductance only increased in the two conditions where BIBP3226 was present. These data indicate that Y1receptor activation plays an important role in the regulation of vascular conductance in the resting rat hindlimb. Furthermore, this effect was of the same magnitude as the 1-adrenoceptor contribution. The differential flow profiles following 1 blockade with and without Y1-receptor blockade supports local differences in receptor distribution.