Time course of changes in sympathetic nerve activity during development of hypertension in spontaneously hypertensive rats

Potential contributions of sympathetic nerve activity to the development of hypertension were studied in the spontaneously hypertensive stroke prone rat (SHRSP). Male SHRSPs were chronically instrumented with bipolar electrodes for measurements of renal (RSNA) and lumbar sympathetic nerve activity (LSNA), and a telemeter was used for measurement of arterial pressure (AP). The time course of changes in AP, heart rate (HR), RSNA, and LSNA were measured continuously and simultaneously from 8 to 12 weeks of age in SHRSPs. AP progressively increased throughout 8–12 weeks in SHRSPs. Diurnal amplitude (difference between daily peak and nadir values) for mean AP gradually increased throughout the experimental period. HR gradually decreased throughout the experimental period without changes in diurnal amplitude for HR. We succeeded in measuring RSNA and LSNA over 4 weeks in several SHRSPs. RSNA and LSNA did not appear to increase in association with the increase in AP over 8–12 weeks of age. Therefore, the contribution of sympathetic nerve activity to the development of hypertension in the SHRSP remains unclear. JSPS Grant.