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Objective: Serotonergic neurons in dorsal raphe nucleus (DRN) is critically involved in sleep-wake regulation.Our previous studies indicated that the suppression of Ca2+ function in DRN could increase NREM sleep, and the elevation of Ca2+ function could reduce both NREM and REM sleep in rats, but the mechanisms remains incomplete.In the view of the fundamental effect of Ca2+ cellular signal transduction on the activity of serotonergic neurons, we presumed that the signaling pathway relating to Ca2+ may be involved in sleep regulation, such as Ca2+-PKC pathway.The present study was designed to determine the role of DRN intracellular Ca2+-PKC signaling pathway in the regulation of wake and sleep.Methods: PKC inhibitor chelerythrine (CHEL, 5 or 10nmol) and/or CaCl2 (25 or 50 nmol) was microinjected (500 nl) into the DRN of freely moving rats, and the sleep parameters were investigated by electroencephalogram (EEG).PKC protein levels in DRN was analyzed by Western-Blot after microinjection of CaCl2.Results: Microinjection of CaCl2 (25, 50nmol) significantly reduced total sleep time, NREM and REM sleep time.Microinjection of CHEL (5 or 10 nmol) significantly increased total sleep time, NREM sleep time particularly light sleep time.The effect of CaCl2 (5nmol)on sleep was inhibited by previously microinjection of CHEL in DRN.PKC protean level in DRN significantly increased after microinjection of CaCl2 (50 nmol) in DRN.Conclusion: These data provide direct evidence that Ca2+-PKC signaling pathway in DRN play important role in sleep-wake regulation.These findings are relevant for designing a drug that could treat excessive sleepiness by promoting alertness.