Pressor Responses to Intracerebroventricular Infusion of Hypertonic NaCl in Renal Hypertensive Rats

Background：The sodium concentration in the central nervous system may play an important role in cardio-vascular function and body fluid regulation. The purpose of this investigation was to examine the effects of intracerebroventricular (ICV) infusion of hypertonic NaCl solutions on the cardiovascular responses in normotensive and 2-kidney, 1 clip (2K1C) renal hypertensive rats. Methods：2K1C hypertension was made by clipping the left renal artery and were used 4 weeks later. Age-matched control rats received a sham treatment. Under thiopental (50 mg/kg, IP) anesthesia, both isotonic and hypertonic NaCl solutions (0.15 M, 0.6 M and 1.2 M) were ICV applied, while blood pressure and heart rate (HR) responses were continuously monitored. Results：Central administration of hypertonic NaCl solution caused an elevation in mean arterial pressure (MAP) and HR in both normotensive and 2K1C hypertensive rats. The response magnitude in the blood pressure was positively correlated to the NaCl concentration in normotensive rats, while the pressor responses to hypertonic NaCl were comparable regardless of the concentration of NaCl in hypertensive rats. Despite of the HR responses were similar in between two groups, the magnitude of the MAP increases were more elevated in hypertensive than in normotensive control rats. Isotonic NaCl solution, when centrally applied, caused an elevation in blood pressure only in hypertensive rats. Conclusion：These results indicate that the central sensitivity to sodium