Abstract
The intraventricular administration of α-adrenoceptive blocker (phentolamine) or dopamine (DA)-β-hydroxylase inhibitor (diethyldithiocarbamate) was found to abolish the most pronounced fall in blood pressure (BP) of freely moving DOCA-salt hypertensive rats (DHR) observed among normotensive or various types of other hypertensive rats after L-DOPA with combination of a peripheral decarboxylase inhibitor (Ro 4-4602). L-DOPA plus Ro 4-4602 markedly reduced the pressor response to electrical stimulation of the posterior hypothalamus, midbrain reticular formation and dorsal medulla oblongata in freely moving, unanesthetized or anesthetized DHR. L-DOPA plus Ro 4-4602 potentiated the depressor component in BP response to the posterior hypothalamic stimulation of the anesthetized DHR. These results suggest that L-DOPA plus Ro 4-4602 markedly lowers BP of DHR due to stimulation of α-adrenoceptor in the brainstem with effluxed noradrenaline after dopamine accumulation in the brainstem noradrenergic neurons and also at least partly due to blockade of the brainstem pressor areas.
