HYPOTHALAMIC REGULATION OF SLEEP IN RATS. AN EXPERIMENTAL STUDY

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Abstract
In a large number of albino rats (Mus norvegicus albinus) the hypothalamus was sharply transsected on different frontal levels. The transsections were inflicted via perforation of the cerebral convexity, so that the lesions were not restricted to the hypothalamus but also involved the overlying parts of the brain. As shown by a number of control expts., however, this additional damage had no significant influence on the postoperative symptoms. In 8 rats in which a characteristic state of sleep was produced, a complete transsection was found in the immediate vicinity of and sometimes involving the mammillary bodies. Unilateral lesions were without effect. More rostrally situated bilateral transsections caused various degrees of drowsiness if they were situated not more than 2 mm. in front of the mammillary bodies. Complete bilateral transsections of the suprachiasmatic part of the hypothalamus caused a complete abolition of the capacity of sleeping. These sleepless animals died within 3 days, apparently from exhaustion. The caudal area of the hypothalamus evidently contains a structure which is of special importance for the maintenance of the waking state, while the preoptic area plays an important part in the function of sleeping. A number of expts. seem to indicate that the latter area may cause sleep only by way of inhibition of the caudal part of the hypo-thalamus.