The dose-response effects of caffeine on sleep in rats.

Caffeine at doses of 0.125, 1.25, 12.5 and 25 mg/kg was administered to rats and the subsequent effects on the sleep-wake cycle were measured. The 12.5 and 25 mg/kg doses of caffeine increased wakefulness, and decreased slow wave sleep-1 (SWS1), SWS2, rapid eye movement (REM) sleep and total sleep time (P less than or equal to 0.05). The 0.125 and 1.25 mg/kg doses of caffeine increased SWS1 at the expense of SWS2 (P less than or equal to 0.05), and did not affect total sleep time in any time period measured. Adenosine or adenosine agonists have been shown to increase SWS2 at the expense of waking or SWS1 with an increase in total sleep time. The effects of caffeine on sleep reported in this study suggest that caffeine administration not only antagonizes the effects of adenosine at the receptor level, but also at the behavioral level.