Age related changes of catecholamines and their metabolites in central nervous system regions of spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats.

Adrenaline (A), dopamine (DA), noradrenaline (NA) the NA metabolite 3,4-dihydroxyphenylethylene-glycol (DHPG) and the DA metabolite 3,4 dihydroxyphenylacetic acid (DOPAC) were assayed in brain regions of male and female WKY and SHR at 6, 14, 28 and 36-40 weeks. Age related differences in catecholamine levels between the two strains were only seen with NA measurements. DOPAC levels were elevated in the striatum of SHR compared to WKY rats at all ages studied which might reflect the known hyperactivity of SHR strain. In the SHR NA but not DHPG levels in several regions, DA and DOPAC levels in midbrain and DA levels in lower brainstem were elevated at 6 weeks of age. These changes may represent a generalized alteration in central catecholamine metabolism in SHR during the early development of hypertension or merely reflect strain differences. It is emphasised that further genetic studies of F2 backcross rats are required to establish an aetiological association between these differences in catechol levels and differences in blood pressure between SHR and WKY rats.