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(Hypertension. 2003;41:744.)
© 2003 American Heart Association, Inc.

Scientific Contributions

Ventrolateral Medulla AT₁ Receptors Support Arterial Pressure in Dahl Salt-Sensitive Rats

Satoru Ito; Makoto Hiratsuka; Kazutoshi Komatsu; Kazuyoshi Tsukamoto; Katsuo Kanmatsuse; Alan F. Sved

From the Second Department of Internal Medicine, Nihon University School of Medicine (S.I., M.H., K.M., K.T., K.K.), Tokyo, Japan, and the Department of Neuroscience, University of Pittsburgh (A.F.S.), Pittsburgh, Pa.

Correspondence to Dr Alan F. Sved, 446 Crawford Hall, University of Pittsburgh, Pittsburgh, PA 15260. E-mail sved{at}pitt.edu

The present study addresses the hypothesis that angiotensin type 1 receptors (AT₁Rs) in the rostral ventrolateral medulla (RVLM) contribute to the elevation of mean arterial pressure (MAP) in Dahl salt-sensitive (DS) rats fed a diet with a high NaCl content. Groups of DS or Dahl salt-resistant (DR) rats were fed diets containing either 0.3% NaCl (LNa) or 8% NaCl (HNa) for 3 weeks. Rats were anesthetized with -chloralose, and the effects of microinjecting the AT₁R antagonist valsartan (Val) or angiotensin II (Ang II) into the RVLM on MAP were measured. Bilateral injection of 100 pmol Val into the RVLM reduced the elevated MAP in the DS-HNa rats by 35 mm Hg. In contrast, Val had no effect on MAP in DS-LNa rats. DR rats were normotensive on either diet; Val injection into the RVLM had no significant effect on MAP in DR-HNa rats but did evoke a small decrease in MAP in DR-LNa rats. Injection of Ang II into the RVLM increased arterial pressure in all groups, but the response was substantially larger in DS-HNa rats. Inhibition of neuronal function in the vicinity of the hypothalamic paraventricular nucleus, a possible source of innervation of the RVLM AT₁R, by local injection with muscimol also produced a substantial decrease in MAP in DS-HNa rats but not in DS-LNa rats or DR rats. Thus, RVLM AT₁Rs appear to contribute to salt-dependent hypertension in DS rats, and the paraventricular nucleus may be a source of this tonic activation.

Key Words: brain • hypertension, essential • hypothalamus • angiotensin • angiotensin antagonist

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