Distinguishing traits in the Sabra hypertension-prone (SBH) and hypertension-resistant (SBN) rats.

Distinct differences in central and peripheral noradrenaline (NA) were observed in the hypertension prone (SBH) and resistant (SBN) strain, derived from the Hebrew University SABRA rats. In the medulla oblongata NA concentration was 90% higher and tyrosine hydroxylase activity 88% lower in SBN when compared to SBH, suggesting marked strain differences in NA turnover. In this area, NA-induced cAMP generation was higher in SBH than in SBN, while the hypothalamus, the reverse situation was present. The relevance of hypertension of the reciprocal cAMP changes is still uncertain. The concentration of NA in heart tissue was significantly higher in SBN than in SBH. Doca-salt treatment caused hypertension and depletion of atrial NA in SBH, but had no effect on either blood pressure or atrial NA in SBN rats. The results suggest that resistance to hypertension in SBN rats is associated with decreased NA turnover in medulla oblongata and reduced activity of cardiac neuronal sympathetic endings.