Journal
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
Volume 315, Issue 4, Pages E478-E488Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpendo.00338.2016
Keywords
light; feeding rhythm; vasopressin; oxytocin; metabolic disorders SCN; PVN; circadian rhythm
Categories
Funding
- Japan Society for the Promotion of Science [266704]
- Strategic Research Program for Brain Sciences [10036069]
- Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT)
- MEXT-Supported Programs for Strategic Research Foundation at Private Universities
- Health Labor Sciences Research Grants from the Ministry of Health, Labor, and Welfare, Japan
- Japan Diabetes Foundation
- Japan Keirin Association
- Collaborative Research in Cooperation with Universities, a grant for Joint Researches in National Institute for Physiological Sciences
- Grants-in-Aid for Scientific Research [16K15182] Funding Source: KAKEN
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Light synchronizes the body's circadian rhythms by modulating the master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. In modern lifestyles that run counter to normal circadian rhythms, the extended and/or irregular light exposure impairs circadian rhythms and, consequently, promotes feeding and metabolic disorders. However, the neuronal pathway through which light is coupled to feeding behavior is less elucidated. The present study employed the light exposure during the dark phase of the day in rats and observed its effect on neuronal activity and feeding behavior. Light exposure acutely suppressed food intake and elevated c-Fos expression in the AVP neurons of SCN and the oxytocin ( Oxt) neurons of paraventricular nucleus ( PVN) in the hypothalamus. The light-induced suppression of food intake was abolished by blockade of the Oxt receptor in the brain. Retrograde tracer analysis demonstrated the projection of SCN AVP neurons to the PVN. Furthermore, intracerebroventricular injection of AVP suppressed food intake and increased c-Fos in PVN Oxt neurons. Intra-PVN injection of AVP exerted a stronger anorexigenic effect than intracerebroventriclar injection. AVP also induced intracellular Ca2+ signaling and increased firing frequency in Oxt neurons in PVN slices. These results reveal the novel neurocircuit from SCN AVP to PVN Oxt that relays light reception to inhibition of feeding behavior. This light-induced neurocircuit may serve as a pathway for forming the circadian feeding rhythm and linking irregular light exposure to arrhythmic feeding and, consequently, obesity and metabolic diseases.
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