BACKGROUND: Sedative and hypnotic chemical drugs prolong the total-sleep time (TST) by a decrease in slow-wave sleep 2 (SWS2) and rapid-eye-movement sleep (REMS) and a relative increase in slow-wave sleep 1 (SWS1).OBJECTIVE: To investigate the effect of the Chinese medicine Zhusha Anshen Wan at different doses on each sleeping state in insomnic rats, and to identify its mode of action in improving sleep.DESIGN, TIME AND SETTING: A randomized controlled study in rats. This study was performed in the Department of Pharmacology of Chinese Materia Medica, Heilongjiang University of Traditional Chinese Medicine during the period from January 2005 to July 2006. MATERIALS: Twenty-four male Wistar rats, weighing (220±5) g, were selected. The main components in Zhusha Anshen Wan, Cinnabaris, Rhizoma Coptidis, Radix Glycyrrhixae, Prepared Radix Glycyrhizae Radix Angelicae Sinensis, and Rehmannia Pride Rhizome, were authenticated by Dr Xiaowei Du, Professor of Pharmacology. ND-97 Digital Polysomnography was purchased from the Shanghai Medical Instrument High Technology Company and Footplate Electrical Stimulator from the Harbin Research Institute of Electrical Instruments.METHODS: Rats were deprived of sleep by using the Footplate Electrical Stimulator. Insomnic rats were randomized into high-, mid- and low-dose Zhusha Anshen Wan groups, eight rats in each group. Animals were administrated with different doses of Zhusha Anshen Wan (equal to crude drug 7.2, 3.6, 1.8 g/kg) consecutively for seven days. MAIN OUTCOME MEASURES: 30 minutes after the last administration, rats of each group suffered 8 hours foot-shocks while electroencephalography signals were recorded using Digital Polysomnography. Total time of waking (W), SWS1, SWS2, REMS and TST were calculated for pre- and post-administration, respectively. RESULTS: All 24 rats were included in the statistical analysis of the results without any loss. In the low-dose Zhusha Anshen Wan group, SWS2 was increased significantly compared with pre-administration. In the middle-dose Zhusha Anshen Wan group, W was decreased significantly, but SWS1, SWS2 and TST were increased markedly compared with pre-administration, and there were significant differences between pre- and post-administration (P < 0.05-0.01). In the high-dose Zhusha Anshen Wan group, the duration of W was significantly decreased after administration, but SWS1, SWS2, REMS and TST were significantly longer than pre-administration (P < 0.05-0.01).CONCLUSION: The effect of Zhusha Anshen Wan on sleeping states is dose-dependent. Zhusha Anshen Wan acts by extending SWS1 and SWS2 to increase the total sleeping time.