Two stainless steel cannulae were implanted into Sprague-Dawley rat’s bilateral CA1 region of hippocampus by using brain stereotaxic technique. At the same time,four copper electrodes were screwed into the skull for electroencephalogram (EEG) recording and two silver wires in the neck muscle for electromyogram (EMG) recording. After drugs were microinjected into hippocampus,sleep-wake cycle was observed by polysomnography. After γ-amino-butyric acid (GABA,0. 75 μg,1.0 μg) was microinjected into CA1 region of hippocampus,wake duration was enhanced (120.7 ± 13.3 min,124.6 ± 19.2 min,P < 0.05),whereastotal sleep time was reduced (119.4 ± 13.3 min,115.4 ± 19.2 min,P < 0.05) ,and deep slow wave sleep duration was also reduced by 53. 3% ( t = 2.451,P < 0.05) or 63. 5% ( t = 3.367,P < 0.01). In contrast, microinjection of bicuculline (Bic),a GAGA_A receptor antagonist into hippocampus led to the opposite effects: total sleep time was increased (165.5 ± 20. 8 min,P < 0.01 ),wake duration was decreased (74. 5 ± 20.8 min,P < 0.01 ),and deep slow wave sleep duration was increased by 79. 6% ( t = 2.600,P < 0.05 ). Microinjection of baclofen (Bac),a GABA_B receptor agonist,had no effect on sleep and could not block the effect of GABA either. These results indicate that GABA is involved in the regulation of sleep-wake cycle and promotes wake in the CA1 region of hippocampus. The effect of GABA on sleep is due to the change of deep slow wave sleep and GABA_A receptor mediates the process.