Effects of inhibitors of the catecholamine synthesis on motor activity in the rat during light and darkness.

Under controlled conditions of light and darkness (12:12 hrs) the influence of inhibitors of the tyrosine-hydroxylase (alpha-MT) and dopamine-beta-hydroxylase (FLA 63) on motor activity were investigated in male Wistar rats at different times of the day. Simultaneously, turnover experiments of the cerebral noradrenaline and dopamine were performed, which revealed diurnal variations within 24 hrs of a day. Both inhibitors showed clear-cut chronopharmacological differences in influencing motor activity, and a phase shift between the darkness-induced increase in motor activity and the maximum turnover rate of the cerebral dopamine was observed.