To explore the molecular and subcellular effects of Angiotensin II during the early phase of an experimental hypertension, biochemical and morphological changes induced by continued administration of subpressoric Angiotensin II doses were traced in rats. After the treatment, the endogenous noradrenalin and dopamine content was changed in various brain regions, the turnover rate of noradrenalin was lowered, and the neuronal 3H noradrenalin uptake was delayed and reduced. Electron microscopy revealed an increase in number and granulation of adrenergic vesicles in the hypothalamus, and characteristic changes at pre- and postsynaptic membrane complexes. The interaction between central effects of angiotensin II and the adrenergic system presumably involves disturbance at the level of neuronal membranes.