Altered renal vascular tone and plasma renin activity due to fastigial and baroreceptor activation.

The effects of stimulating the cerebellar fastigial nucleus in altering renal vascular resistance were assessed at three levels of carotid sinus pressure (CSP). In alpha-chloralose-anesthetized, vagotomized, and salt-depleted cats, renal vascular resistance changes were established by perfusing the isolated carotid sinus at high (197 +/- 17 mmHg), medium (117 +/- 8 mmHg), and low (60 +/- 7 mmHg) pressure. The hemodynamic state of the perfused kidney was determined from flow-pressure curves. In relative units, the flow resistance in the renal bed was for low CSP, 2.60 PRU100, for medium CSP, 2.25 PRU100, and for high CSP, 1.22 PRU100. The fastigial pressor response was imposed at each flow-presure determination with or without superior cerebellar peduncle lesions. An increase in the resistance with the fastigial stimulation was noted at each of the three hemodynamic states; 14% at low, 26% at medium, and 22% at high CSP. With increased renal vascular resistance evoked through the baroreflex, there was an increase in plasma renin activity. The rise in plasma renin activity could be attributed in large part to an increase in sympathetic renal nerve activity wherein the fastigial pressor response shared a synergistic action at medium and high carotid sinus pressure. The effect of the fastigial stimulation on renal vascular resistance and renin secretion was abolished by transections of the superior cerebellar peduncles.