[Physiology of sleep-wakefulness rhythms].

As the most important site for sleep-wakefulness change, the role of the hypothalamus is particularly emphasized based on our long term experimental data. After rostral midbrain transection, ECoG of the isolated forebrain recovered sleep-wakefulness change, with circadian rhythm, one week after transection. In this preparation, after additional bilateral preoptic or posterior hypothalamic lesions, ECoG "insomnia" or "coma" pattern appeared, respectively. Therefore, the mechanism of sleep-wakefulness change of the forebrain primarily does not depend on the lower brain stem structures such as the raphe nuclei and midbrain reticular formation. Hypothalamic sleep-wakefulness mechanism usually receives strong influence from the suprachiasmatic nucleus, but it can exert its own ultradian "rhythms" (very irregular though) in intact rats or in rats with suprachiasmatic lesions.