DIURNAL-VARIATION IN THE DOPAMINE LEVEL OF RAT-BRAIN AREAS - EFFECT OF SODIUM PHENOBARBITAL

The levels of dopamine in the caudate nucleus, cerebellum, cortex and midbrain were determined every three hours in control rats nd in rats pretreated with sodium phenobarbital over a twenty-four hour period. All animals were adapted for a minimum period of three weeks to an environmental room equipped with a programmed 12 hour dark - 12 hour light illumination cycle. The level of dopamine was highest during the dark phase and lowest during the light phase of the photoperiod in all the brain areas studied. Sodium phenobarbital pretreatment increased dopamine level in all the brain areas studied at most times, particularly during the dark phase and enhanced the circadian rhythmicity of dopamine levels in the cortex, cerebellum and midbrain. © 1979.