EFFECTS OF CHEMICAL-STIMULATION OF THE ROSTRAL VENTROLATERAL MEDULLA ON CEREBRAL AND RENAL MICROCIRCULATION IN SPONTANEOUSLY HYPERTENSIVE RATS

We investigated whether microcirculatory responses elicited by excitat ion of intrinsic neurons in the rostral ventrolateral medulla (RVLM) a re altered in spontaneously hypertensive rats (SHR). SHR and Wistar-Ky oto rats (WKY) were anesthetized with chloralose, paralyzed with tuboc urarine, and artificially ventilated. Cerebral and renal blood flows ( CBF and RBF) were simultaneously measured using laser-Doppler flowmetr y. Chemical stimulation of the RVLM neurons by microinjection of L-glu tamate increased arterial pressure (AP) and heart rate in both SHR and WKY. Stimulation of the RVLM?I neurons also elicited stimulus-locked increase in CBF and decrease in RBF in both groups. The % changes in C BF and RBF were dose-dependent as stimulus intensity was increased and did not differ significantly between the SHR and WKY groups. Cerebral and renal vascular resistance (CVR and RVR) levels were calculated fr om changes in CBF or RBF and those in mean AP. The percent reduction i n CVR and percent elevation in RVR were dose-dependent and did not dif fer significantly between the two groups. The data indicate that cereb ral and systemic microcirculatory responses elicited by excitation of the RVLM neurons do not differ between SHR and WKY. (C) 1998 Elsevier Science B.V. All rights reserved.