Differential effect of benserazide on catecholamine concentrations in the rat pineal, cerebral cortex and hypothalamus.

The effect of benserazide, an aromatic L-amino acid decarboxylase inhibitor, has been investigated simultaneously on the noradrenaline content of the pineal, hypothalamus and cerebral cortex of the rat. The dopamine concentration of the hypothalamus was investigated in the same animals. Benserazide had no effect on pineal noradrenaline content throughout the light phase and the early part of the dark phase but caused a drastic reduction in the latter part of the dark period. The drug had no significant effect on noradrenaline or dopamine contents of the hypothalamus. Benserazide treatment caused a large reduction in the noradrenaline content of the cerebral cortex throughout 24 hr. However, this effect is unlikely to be due to a differential penetration of benserazide into the brain areas as a similar degree of decarboxylase inhibition was observed in all three tissues.