Increased Noradrenaline Content of Hypothalamic Nuclei in Association with Worsening of Hypertension after High Sodium Intake in the Young Spontaneously Hypertensive Rat

1. High sodium intake results in an exacerbation of hypertension accompanied by evidence of increased peripheral sympathetic activity in the young spontaneously hypertensive rat (SHR) of the Okamoto strain. 2. To examine the hypothesis that high sodium intake increases peripheral sympathetic activity via an influence on central noradrenergic pathways involved in cardiovascular regulation, the effect of dietary sodium intake on noradrenaline stores of individual hypothalamic nuclei was examined in young SHR. 3. After 2 weeks of high sodium intake, the noradrenaline content of the anterior and dorsomedial hypothalamic nuclei of SHR was increased when compared with SHR receiving normal sodium intake. Increases in the noradrenaline content of anterior hypothalamic nucleus persisted at 4 weeks. No changes were seen in other regions examined. 4. These observations lend support to the hypothesis that sodium and the sympathetic nervous system have synergistic effects in the pathogenesis of hypertension in the SHR.