Vesicovascular reflexes in the spontaneously hypertensive rat

We investigated the effects of hypertension and acute blood pressure changes on rats' vesicovascular reflexes (VVRs).

Twelve-week-old male Wistar rats and spontaneously hypertensive rats (SHRs) were anesthetized with urethane, and underwent real-time cystometry and blood pressure monitoring. The SHRs were administered nifedipine or valsartan intravenously. The Wistar rats were administered intravenous noradrenaline continuously. The intercontraction intervals, maximum detrusor pressures, blood pressure during the voiding and the urine storage phases, blood pressure elevations associated with the VVRs, and arterial pulses were assessed. Plasma adrenaline and noradrenaline concentrations were measured using HPLC. The degree of atherosclerosis was assessed histologically based on the aortic wall thickness.

Blood pressure elevations associated with the voiding reflexes were significantly lower and intercontraction intervals were significantly shorter in the SHRs compared with the Wistar rats. Although nifedipine and valsartan reduced the systolic blood pressure and noradrenaline increased the systolic blood pressure, they failed to alter the blood pressure elevations associated with the VVRs and the intercontraction intervals. No significant differences occurred with respect to the maximum detrusor pressures among the experimental groups. The reflected waves' shapes were normal in the Wistar rats, but they almost disappeared in the SHRs. The aortic walls were significantly thicker in SHRs compared with those in Wistar rats.

The blood pressure elevations associated with the VVRs were lower in the SHRs than in the Wistar rats. Acute blood pressure reductions failed to ameliorate the blood pressure elevations associated with VVRs in the SHRs.