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This diagram from Neuroscience: Exploring the Brain by Bear, Connors, and Paradiso shows the various effects of lesions in different areas of the rat hypothalamus. Lesions of the lateral hypothalamus result in anorexia, while lesions of the ventromedial hypothalamus cause obesity.

Obesity results when energy intake consistently exceeds energy expenditure. In recent decades, various mechanisms behind feeding regulation (particularly those involving satiety hormones such as leptin, orexin, and cholecystokinin) have been presented. Before analyzing the current research, it is beneficial to consider the historical background of the research regarding regulation of feeding behavior.

A.W Hetherington and S.W Ranson conducted one of the first experiments studying regulation of feeding behavior in the 1940s in which they used a Horsely-Clark instrument to make hypothalamic lesions. They found that lesions in the lateral hypothalamus caused the rats to stop eating, while lesions in the ventromedial hypothalamus caused the animals to overeat, leading to obesity. At this time, researchers developed a rather simple model for feeding behavior based on these observations. They termed the lateral hypothalamus the hunger center and the ventromedial hypothalamus the satiety center. Despite this interesting observation, researchers knew that for a connection to exist between feeding behavior and body fat, they would need to identify some sort of bloodborne signal.

Author(s)

Year

Title

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Hetherington, A.W. and Ranson, S.W.

1942

The Relation of Various Hypothalamic Lesions to Adiposity in the Rat

J. Comp. Neur. 76: 475-499

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