On the localization of the hypotensive effect of L-dopa

Abstract

Mean arterial blood pressure was recorded in anaesthetized rats before and after a mid-collicular transection of the brain (decerebration). Basal blood pressure was not changed by the decerebration. Injection of l-dopa (200 mg/kg, i.p.) after peripheral dopa decarboxylase inhibition by l-α-hydrazino-α-methyl-β-(3,4-dihydroxyphenyl) propionic acid (MK 486, 100 mg/kg, i.p.) resulted in a significant reduction of arterial pressure to the same level in both control (sham- operated) and decerebrated rats after 30 min. In other experiments, anaesthetized rats were spinalized at C7-Th1. Basal blood pressure became significantly lower than in control and decerebrated rats and l-dopa after MK 486 in the same doses did not affect blood pressure. Biochemical determinations of noradrenaline and dopamine showed that administration of l-dopa after MK 486 to decerebrated rats in the same doses as in the blood pressure experiments resulted in a pronounced increase of dopamine in both parts of the brain.