Noradrenaline concentration and turnover in nuclei of the hyothalamus and the medulla oblongata at two stages in the development of renal hypertension in the rat.

The noradrenaline concentration and the alpha-methyl-para-tyrosine (alpha-MPT)-induced disappearance of noradrenaline were determined in several nuclei of the hypothalamus and the medulla oblongata of renal hypertensive rats (two-kidney Goldblatt hypertension). A decreased alpha-MPT-induced disappearance of noradrenaline was found in the nucleus interstitialis striae terminalis and the nucleus paraventricularis 3 days after renal artery constriction, when blood pressure was slightly, but significantly higher than that of sham operated rats. At this stage the alpha-MPT-induced disappearance of noradrenaline was enhanced in the nucleus commissuralis and the A1-region of hypertensive rats while the noradrenaline concentration in the A1-region was significantly elevated. No significant differences were found in both parameters in hypothalamic and medullary nuclei 3.5 weeks after the operation, when hypertension had fully developed. These findings are indicative of the occurrence of transient changes in the activity of noradrenergic neurons located in the medulla oblongata and projecting to the hypothalamus during the initiation of the development of two-kidney Goldblatt hypertension.