THE ROLE OF PURINERGIC AND ADRENERGIC TRANSMITTERS OF THE SYMPATHETICSYSTEM IN THE CONTROL OF ARTERIAL BLOOD-PRESSURE VARIABILITY

Variability of mean arterial pressure (MAP) was examined in chronicall y instrumented, conscious, freely moving rats with pharmacologically a ltered efferent sympathetic influences on the cardiovascular system. M AP was recorded for 30 min beat-to-beat, using a computer under both c ontrol and experimental conditions: after administration of adrenocept or antagonists (prazosin or phentolamine) or under P2X receptor inacti vation produced either by desensitization with alpha,beta-methylene AT P or by PPADS blockade. Inhibition of adrenergic sympathetic effects o n the cardiovascular system produced long-lasting and stable decrease in MAP. Prazosin did not modify MAP variability whereas phentolamine e nhanced it. Under P2X receptor desensitization MAP decreased, the hypo tensive effect being accompanied by a significant increase in MAP vari ability. A similar increase in MAP variability was observed after PPAD S administration, while MAP level was not changed. Administration of P PADS in combination with phentolamine increased MAP variability more s ignificantly than each of the drugs given separately. Changes in MAP v ariability under the various experimental conditions were not consiste ntly correlated with changes in heart rate variability. We propose tha t ATP, being a mediator of sympathetic vasoconstriction, participates in baroreceptor-induced stabilization of MAP level. (C) 1998 Elsevier Science B.V. All rights reserved.