Asynchrony in the diurnal rhythms of dopaminergic D-2 receptors in different brain regions of the rat

Diurnal variations of dopaminergic D-2 receptors have been described in the striatum of rats, while other dopaminergic regions remain unstudied. Diurn al variations of dopamine D-2 receptors in the striatum, frontal cortex, an d amygdala of the rat, were characterized by the stereospecific binding of [H-3]-spiperone. Clear rhythms were found in all these areas, but asynchron ous to each other. Striatal receptors had diurnal variations with a single peak at 00:00 hours. Frontal cortex receptors showed two peaks at 00:00 and 12:00 hours. Amygdaline complex receptors had two peaks at 18:00 and 06:00 hours. Saturation binding curves and their Scatchard analysis indicated th at the diurnal variations in [H-3]-spiperone binding are related to changes in receptor density rather than its affinity. The diurnal variations async hrony in [H-3]- spiperone binding to dopaminergic D-2 receptors from differ ent neural regions, suggest different regulation in each area. Other functi onal implications of these rhythms remains to be established.