Intravenous infusions of nutrients and sleep in the rat: an ischymetric sleep regulation hypothesis.

Unrestrained food-deprived rats received their daily caloric needs through continuous or discontinuous intravenous infusions of specific nutritive substances over a period of 3 consecutive days each, and the effect on sleep monitored by electroencephalogram was examined. Continuous glucose or lipid infusions did not affect the daily sleep quotas. Amino-acid infusion brought about a significant increase in paradoxical sleep (PS), whereas slow-wave sleep (SWS) remained unchanged. Rats that received the highly nutritive composite solution showed significant increase in both SWS and PS. The same increase in SWS and PS was observed when exogenous insulin was coinfused with continuous infusion of glucose or when glucose infusions were discontinuous. These findings suggest that sleep might be related to both the nature and the degree of utilization of the circulating metabolites. A model for the action on sleep of nutrients at the systemic level was proposed; only when substances are metabolized is there a direct effect on sleep mechanisms.