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

We investigated the effects of neurons in the rostral and caudal ventr olateral medulla (RVL and CVL) on cerebral and renal microcirculation in rats. Rats were anesthetized with chloralose, paralyzed with tubocu rarine, and artificially ventilated. Cerebral and renal blood flows (C BF and RBF) were measured simultaneously using laser-Doppler flowmetry . Chemical stimulation of the RVL neurons by microinjection of the exc itatory amino acid L-glutamate increased arterial pressure (AP), where as that of the CVL neurons decreased AP. Stimulation of the RVL neuron s also elicited a stimulus-locked increase in CBF and a decrease in RB F. The percent change in CBF and RBF was dose-dependent as stimulus in tensity was increased. Cerebral and renal vascular resistance (CVR and RVR) levels were calculated from changes in CBF or RBF and changes in mean AP. The percent reduction in CVR and percent elevation in RVR we re also dose-dependent. Chemical stimulation of the CVL neurons elicit ed a stimulus-locked decrease in CBF and an increase in RBF. The perce nt reduction in CBF and percent elevation in CVR were dose-dependent. The percent reduction in RVR was also dose-dependent, while the percen t elevation in RBF was not significant. Blood withdrawal reduced AP by a similar degree to CVL stimulation, but did not significantly decrea se CBF. The results suggest that RVL and CVL neurons integrate cerebra l and systemic microcirculation.