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Department of Anesthesiology, University of Hirosaki School of Medicine, Japan
Address correspondence and reprint requests to Tetsuya Kushikata, MD, Department of Anesthesiology, University of Hirosaki School of Medicine, 5 Zaifu-cho, Hirosaki, Japan. Address e-mail to tkush{at}df6.so-net.ne.jp
2 Adrenoceptor activity is involved in the mechanism of anesthesia. Clonidine, a
2 adrenoceptor agonist, and yohimbine, a
2 adrenoceptor antagonist, increase and decrease barbiturate-induced sleep times. In this study, we examined the effects of these drugs on propofol-induced sleep time. One-hundred-eighteen male Wistar rats weighing 320400 g were used. Rats received saline, yohimbine (1, 0.1, or 0 mg/kg), or clonidine (300, 30, 3, or 0 µg/kg) intraperitoneally followed by 60 mg/kg of propofol in various combinations. In two series of experiments, either sleep time or prefrontal cortex norepinephrine release (microdialysis) was measured. One milligram/kilogram of yohimbine decreased propofol-induced sleep time to approximately 70% of control, and this was accompanied by an increase in perfusate norepinephrine of approximately 240% of control. Clonidine increased sleep time approximately 260% (300 µg/kg) and approximately 170% (30 µg/kg), and this was accompanied by a decrease (approximately 60% in both doses) in perfusate norepinephrine. In the present study, we show that the
2 antagonist, yohimbine, decreased and the
2 agonist, clonidine, increased propofol-induced sleep times. These changes were essentially mirrored in both groups by changes in norepinephrine release in the prefrontal cortex.
IMPLICATIONS: Central
2 adrenoceptor is thought to be involved in several IV anesthetics-induced sleep. In this study, activation of the receptor increased the propofol-induced sleep time, whereas its inhibition decreased the sleep time. The results provide further evidence that the
2 receptor is a good tool to elucidate the mechanism of anesthetics-induced sleep.
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