1. Activity of peripheral and central catecholaminergic neurons was studied in spontaneously hypertensive rats (SHR) and deoxycorticosterone (DOCA)—salt hypertensive rats.
2. In young SHR (4 weeks) the plasma values of both noradrenaline and dopamine-β-hydroxylase activity were increased compared with those of normotensive rats of the Wistar/Kyoto strain. Total catecholamines (mostly adrenaline) were not significantly different.
3. In the adrenal glands of 2-weeks-old and 4-weeks-old SHR activities of tyrosine hydroxylase, dopamine-β-hydroxylase, phenylethanolamine-N-methyl transferase were decreased, compared to Wistar/Kyoto rats.
4. The adrenaline-forming enzyme was elevated in the A1 and A2 regions of the brain stem of 4-weeks-old SHR and in the A1 region of adult DOCA—salt hypertensive rats.
5. In the adrenal glands of adult DOCA—salt hypertensive rats tyrosine hydroxylase activity was increased.
6. These results implicate peripheral noradrenaline-containing neurons and central adrenaline-containing neurons in the development of genetic and experimental hypertension in rats.