Neonatal monosodium glutamate dosing alters the sleep-wake cycle of the mature rat.

Alterations of the sleep-wake cycle have been studied in male adult rats after neonatal administration of monosodium glutamate (MSG; 4 X 4 mg/g body wt.). Results indicated that MSG treatment caused: an almost complete disappearance of ACTH and alpha-MSH immunoreactive (IR) perikarya in the rostral part of the arcuate nucleus; an increase in total sleep duration with a more pronounced effect on paradoxical sleep. Regarding circadian rhythmicity there was a trend to a decomposition of the 24 h period into ultradian components (12 h, 8 h, 6 h harmonics). The participation of pro-opiomelanocortin peptides in sleep regulation is discussed.