There have been proved that the ventrolateral preoptic area (VLPO) of the hypothalamus is a homeostatic aspect of sleep regulation and adenosine is an endogenous sleep factor.The sleep promoting effects of adenosine are mainly mediated by A1 and A2A adenosine receptors (ARs) with region-dependent.Our laboratory recently found that A1ARS, no or poor of A2AARS, were expressed in the VLPO.In order to detect the effect of A1ARS on sleep-wake regulation in VLPO, the electroencephalogram (EEG) recoding was used.Two stainless steel cannulae were implanted into Sprague-Dawley rats bilateral VLPO with brain stereotaxic technique.Four copper electrodes were screwed into the skull for EEG recoding and two silver wires in the neck muscle for etectromyogram (EMG) recording.The EEG/EMG signals were recorded by the MP 150 data acquisition system and analysised by SLEEPSIGN sofeware.The results show that the wakefulness was enhanced and the sleep was reduced after adenosine microinjected into VLPO.Microinjection of nitrobenzyl-thio-inosine (NBTI), an adenosine transport inhibitor, induces the similar effects as adenosine does.Activating adenosine A1 receptor with its specific agonist, N6-cyclohexyladenosine, produced an enhancement in wakefulness with concomitant reduction in sleep.Conversely, blockade adenosine A1 receptor with its antagonist, 1,3-dimethyl-8-cyclopenthylxanthine, increases sleep time.From the above, the results indicate that adenosine promotes wakefulness in VLPO via A1 receptor.