The effect of binge eating on orexigenic neurons of the lateral hypothalamus

Rowe, Todd McLean (2017) The effect of binge eating on orexigenic neurons of the lateral hypothalamus. Masters thesis, Memorial University of Newfoundland.

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Abstract

Binge eating is a form of disordered eating involving excessive caloric intake in a brief period of time, typically from palatable, calorie-dense foods. The underlying neural mechanisms controlling this behavior are poorly understood, but likely involve both homeostatic and hedonic feeding circuitry. The lateral hypothalamus contains orexin and melanin-concentrating hormone (MCH) neurons, both of which are orexigenic neurons that also play roles in stress, reward and motivation. It is possible that activation of these neurons is responsible for the development or maintenance of binge eating behavior. To test this, we established an animal model of binge eating by providing rats with three schedules of intermittent access to a palatable, high fat diet (HFD): 6 daily exposures (1wDaily), 6 exposures over 2 weeks on Mondays, Wednesdays and Fridays (2wMWF), and 18 exposures over 6 weeks (6wMWF). Rats eagerly consumed the diets upon presentation following repeated exposures, consuming up to a quarter of their daily calories in a one-hour food exposure, indicative of binge-like behavior. Following 1wDaily or 2wMWF feeding, there was no apparent effect of HFD on orexin neurons, but after 6wMWF feeding, orexin neurons were significantly hyperpolarized in the HFD group compared to those in controls. However, we did not observe any changes in MCH neurons. This suggests that long-term, but not short-term intermittent access to a palatable diet high in fat induces changes in orexin neurons. In conclusion, our results suggest that orexin neurons are unexpectedly inhibited by prolonged exposure to feeding patterns that induce binge eating. This may be a homeostatic response to repeated binge eating.

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