Ventromedial hypothalamic lesions and weight gain in rats: Absence of a static phase

Hallonquist, John D.; Brandes, Jack S.

doi:10.1016/0031-9384(81)90244-4

Cited by 9 publications

(1 citation statement)

References 34 publications

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“…The pattern of feeding and weight gain over time after the Arc NPY-SAP injection was similar to the classic pattern described in rats with other types of lesions in the mediobasal hypothalamic region, consisting of a dynamic phase of hyperphagia and rapid weight gain, followed by a static phase during which daily food intake and rate of weight gain are reduced to levels more similar to control values (22). Sleep experiments described above were conducted during the dynamic phase of weight gain.…”

Section: Resultssupporting

confidence: 72%

Circadian integration of sleep-wake and feeding requires NPY receptor-expressing neurons in the mediobasal hypothalamus

Wiater

Mukherjee

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

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Sleep and feeding rhythms are highly coordinated across the circadian cycle, but the brain sites responsible for this coordination are unknown. We examined the role of neuropeptide Y (NPY) receptor-expressing neurons in the mediobasal hypothalamus (MBH) in this process by injecting the targeted toxin, NPY-saporin (NPY-SAP), into the arcuate nucleus (Arc). NPY-SAP-lesioned rats were initially hyperphagic, became obese, exhibited sustained disruption of circadian feeding patterns, and had abnormal circadian distribution of sleep-wake patterns. Total amounts of rapid eye movement sleep (REMS) and non-REMS (NREMS) were not altered by NPY-SAP lesions, but a peak amount of REMS was permanently displaced to the dark period, and circadian variation in NREMS was eliminated. The phase reversal of REMS to the dark period by the lesion suggests that REMS timing is independently linked to the function of MBH NPY receptor-expressing neurons and is not dependent on NREMS pattern, which was altered but not phase reversed by the lesion. Sleep-wake patterns were altered in controls by restricting feeding to the light period, but were not altered in NPY-SAP rats by restricting feeding to either the light or dark period, indicating that disturbed sleep-wake patterns in lesioned rats were not secondary to changes in food intake. Sleep abnormalities persisted even after hyperphagia abated during the static phase of the lesion. Results suggest that the MBH is required for the essential task of integrating sleep-wake and feeding rhythms, a function that allows animals to accommodate changeable patterns of food availability. NPY receptor-expressing neurons are key components of this integrative function. arcuate nucleus; NPY-saporin; obesity; rapid eye movement sleep FEEDING AND VIGILANCE (sleep-wake) states are rhythmically expressed across the circadian cycle, and their rhythms are highly integrated (3,64,75). Integration of sleep-wake and feeding rhythms is of fundamental importance for survival. Indeed, a wakeful state is an intrinsic requirement for feeding and foraging behavior, and, in a changeable environment, only close communication between these particular rhythms would permit an animal to respond adaptively and opportunistically to changing patterns of food availability. Although the suprachiasmatic nucleus of the hypothalamus (SCN) has an acknowledged role in establishing and maintaining circadian rhythms (47,63,83), including sleep-wake rhythms (15), entrainment of circadian food-anticipatory rhythms does not require the SCN (79,82), supporting the possibility that integration of sleep-wake and feeding also occurs outside the SCN. Furthermore, integration of physiological signals required to derive rhythms compatible with homeostatic requirements is likely to occur outside the SCN (6,48,75), as this arrangement would provide maximum flexibility for responding to varying challenges.Surprisingly few experiments have attempted to determine sites responsible for integration of sleep and feeding rhythms. However, a large body o...

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Section: Resultssupporting

confidence: 72%