Hypophysectomy does not disturb the sleep-waking cycle in the cat.

The ablation of the hypophysis does not disturb the basic waking-sleep cycle. Further, this intervention fails to modify the recovery of sleep after instrumental paradoxical sleep deprivation as well as after injection of 5-hydroxytryptophan in parachlorophenylalanine-pretreated insomniac cats. These results demonstrate that the hypophysis does not play a significant role in sleep mechanisms. We discuss these data in view of a possible regulation of the sleep-waking cycle by hypothalamo-hypophyseal hormones.

Increase of paradoxical sleep induced by microinjections of ibotenic acid into the ventrolateral part of the posterior hypothalamus in the cat.

In order to study putative hypothalamic mechanisms of sleep-waking cycle regulation we injected a neural cell body toxin--ibotenic acid (IBO), 40 to 200 micrograms--into the ventrolateral part of the posterior hypothalamus (HVL). This injection induced a dramatic biphasic and transient hypersomnia immediately after the disappearance of the anesthesia (14 to 24 hours after the injection). The duration of hypersomnia was dose dependent. Its first period was characterized by an increase in paradoxical sleep (PS) (300%). Then, during the second phase, PS disappeared and there was a subsequent increase of slow sleep (SWS) (60%). Finally, on the third day, all cats recovered control level of PS and SWS while, 3 weeks later, the histological analysis revealed the great loss of cell bodies in the HVL in all cats.

Effects of electrolytic lesion of hypothalamic paraventricular nucleus and its related areas on the sleep waking cycle in the cat.

In order to study putative hypothalamic mechanisms of sleep waking cycle regulation we destroyed, by electrolytic coagulation, a large part of the medial hypothalamus overlapping the paraventricular nucleus in 6 adult cats. We never observed any modification of light slow wave sleep. Three of the six cats presented no paradoxical sleep (PS) impairment, despite an almost total destruction of neurophysin-immunoreactive cells of PVN in two cats and marked signs of diabetes insipidus in the third. Further, in the other three animals a statistically significant decrease of daily quantities of PS and deep slow wave sleep (SWS2) were related to an extensive destruction of the anterior hypothalamic area. These results suggest lack of influence of the PVN in sleep regulation and an involvement of the anterior hypothalamus in the onset of SWS2 and PS.

[Increase of paradoxical sleep, induced by injection of ibotenic acid in the ventrolateral posterior hypothalamus in the cat]. / Augmentation du sommeil paradoxal, induite par l'injection d'acide iboténique dans l'hypothalamus ventrolatéral postérieur, chez le chat.

The intratissular injection of ibotenic acid into the ventrolateral part of the posterior hypothalamus induced a dramatic biphasic and transient hypersomnia immediately after disappearance of the anaesthesia (14 to 24 hrs. after injection). The duration of hypersomnia was related to the dose of neurotoxin injected. Its first period was characterized by an increase in paradoxical sleep (PS) (300%). Then, during the second phase, PS disappeared and there was a subsequent increase of slow wave sleep (SWS) (60%). Finally, on the third day, all cats recovered control level of PS and SWS.