Increased catecholamine metabolism in the locus coeruleus of young spontaneously hypertensive rats.

Young, 4-week-old spontaneously hypertensive rats (SHR) had significantly higher concentrations of dopamine and 3,4-dihydroxyphenylacetic acid and a faster rate of accumulation of L-dihydroxyphenylalanine after decarboxylase inhibition in the locus coeruleus than age-matched Wistar-Kyoto rats, whereas the norepinephrine levels were similar to each other. In the brainstem, these changes were restricted to the locus coeruleus and were not present in adult, 14-week-old rats with established hypertension. These results are suggestive of a noradrenergic overactivity in the locus coeruleus of young SHR, coinciding with the development of the hypertension.