[H-3] DOPAMINE UPTAKE IN ADRENAL CHROMAFFIN CELLS OF MICE UNDER ACUTE IMMOBILIZATION STRESS - DIFFERENCE BETWEEN DARK AND LIGHT PERIOD

[H-3]Dopamine uptake under acute immobilization stress in adrenal chromaffin cells of mice was examined in vivo during dark (at 06.00 h) and light period (at 18.00 h). In the dark period, acute immobilization suppressed the uptake of [H-3]dopamine in adrenal chromaffin cells, white in the light period, when steroid surge suppresses the uptake, it caused slight recovery of high-affinity uptake. Adrenal denervation prevented the suppression by immobilization in the dark period. Present results indicate that at 06.00 h, high-affinity uptake was inhibited by cortical steroids induced by immobilization while at 18.00 h, a larger amount of cortical steroid, steroid surge plus immobilization, caused an enhancement of the uptake. Sympathetic innervation is necessary to reveal the steroid effects.