Abstract

The present report suggests that a reciprocal relationship might exist between neuronal catecholamine concentrations and catecholamine turnover. This relationship was unmasked by studying the turnover rate of catecholamine stores with an isotopic and a nonisotopic method in rats treated with drugs that alter the steady-state levels of the catecholamines. Monoamine oxidase inhibitors increased the levels of norepinephrine (NE) and dopamine in brain and NE in heart and significantly decreased the turnover rates of these amines. The turnover rate of heart NE in rats given reserpine 6 or 8 days before measuring turnover was double that of control rats, whereas the NE levels were reduced by almost 30%.