Forearm blood flow responses to neuropeptide Y, noradrenaline and adenosine 5 '-triphosphate in hypertensive and normotensive subjects

Neuropeptide Y (NPY), noradrenaline (NA) and adenosine 5'-triphosphate (ATP ) are important cotransmitters in the sympathetic nervous system, which has a central role in cardiovascular control. In order to evaluate if hyperten sion is associated with alterations in vascular responses to sympathetic co transmitters we studied the effects of intra-arterial infusion of NPY, NA a nd ATP on forearm blood flow. Blood flow was measured by venous occlusion p lethysmography in six hypertensive (mean arterial blood pressure (MAP) 113 +/- 4 mmHg) and six matched normotensive subjects (MAP 97 +/- 3 mmHg). NPY and NA significantly reduced forearm blood flow, while a powerful increase was seen with ATP. Forearm vascular resistance, calculated as MAP divided b y forearm blood flow, was significantly increased by NPY and NA and strongl y reduced by ATP. There was no difference between hypertensive and normoten sive subjects in response to either transmitter. In conclusion, vascular re activity to intra-arterial administration of NPY, NA and ATP seems to be in tact in hypertensive patients without metabolic aberrations.