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

Sep 2, 2011American journal of physiology. Regulatory, integrative and comparative physiology

Daily rhythm coordination of sleep, wakefulness, and eating depends on specific neurons in the brain's energy control center

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Abstract

NPY-saporin lesions in the mediobasal hypothalamus resulted in sustained disruption of circadian feeding and sleep-wake patterns in rats.

NPY-saporin-lesioned rats initially experienced increased food intake and became obese.
Disruption of circadian feeding patterns occurred alongside abnormal sleep-wake distributions.
The total amounts of rapid eye movement sleep (REMS) and non-REM sleep (NREMS) did not change, but REMS timing shifted permanently to the dark period.
Circadian variation in NREMS disappeared after the lesions, indicating a specific disruption in sleep regulation.
Feeding restrictions did not alter sleep-wake patterns in lesioned rats, suggesting that sleep disturbances were not linked to changes in food intake.
Sleep abnormalities continued even after the initial hyperphagia decreased, indicating lasting effects of the lesions.

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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.

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

Abstract

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