Time-dependent effects of actinomycin S3 on sleep and brain concentrations of 5-hydroxytryptamine in the rat

Abstract

Changes in the sleep pattern were investigated in rats given actinomycin S3 (AcS3, 0.25 mg/kg, intraventricularly), an inhibitor of RNA synthesis, at 0000, 0600, 1200, and 1800. The amounts of slow-wave (SS) and paradoxical sleep (PS) were increased during the dark period (1800 to 0600) in the groups treated at 0000, 0600, and 1200. In the 1800 injected group, PS was decreased. 5-Hydroxytryptamine (5-HT) was determined in the 0600 injected group. The 5-HT concentration in the AcS3-treated group was twofold higher than in the control group at 1800 (12 h after administration) in the cerebral cortex and lower brain stem but returned to control values at 0000 (18 h after) while sleep time continued to increase. Thus, AcS3 affected the circadian rhythm of the sleep-wake cycle. The increase of sleep time in the dark period was independent of changes in brain 5-HT content.