抄録
Circadian rhythms of locomotor activity and plasma corticosterone were determined simultaneously in individual rats which were injected intracerebroventricularly with 6-hydroxy-dopamine (6-OHDA), a specific depletor of catecholamines. Under light-dark cycles (LD), 6-OHDA treated rats showed essentially normal circadian rhythms of both functions. Under 200 1ux continunous light (LL) the locomotor activity in the drug-treated rats ran freely with a period slightly longer than 24.0 hr, free-running parameters such as level, amplitude and period of the locomotor activity being the same with those of control rats. The circadian rhythm of plasma corticosterone in control rats also ran freely under LL, resulting in a reversal of their phase after 12 days exposure to LL. However, the rhythm disappeared in 6-OHDA treated rats under LL. These results suggest that the brain catecholaminergic components are indispensable for the circadian rhythm of plasma corticosterone to freerun normally under LL, but are dispensable under LD. A pausible model consisting of two oscillators is proposed to explain these findings.
