Neural and hormonal mechanisms regulating food intake.

In this outline of the neural control of food intake, no attempt has been made to provide a comprehensive survey of the literature since there are several symposia and reviews available which summarize the extensive work in this field (Grossman, 1975; Novin et al. 1976; Silverstone, 1976; Morgane & Panksepp, 1980; Hoebel & Novin, 1982). Instead some current concepts of the neural control of food intake are presented. Almost all the work on the neural control of feeding has been carried out on laboratory animals but experiments on farm animals will be emphasized where appropriate. The brain region most extensively investigated in relation to feeding behaviour is the hypothalamus. Hetherington & Ranson (1942) and Brobeck et al. (1943) demonstrated that bilateral lesions in the ventromedial region of the rat’s hypothalamus (VMH) resulted in hyperphagia and adiposity, and Anand & Brobeck (1951) reported that bilateral lesions in the lateral hypothalamus of rats and cats produced profound adipsia and aphagia. These seminal experiments led to the concepts of excitory and inhibitory centres in the hypothalamus with a ‘satiety centre’ in the ventromedial region and a ‘feeding centre’ in the lateral hypothalamus (Steller, 1954). These early concepts have been modified and replaced by the hypothesis that although the hypothalamus is a major part of the neurological system involved in the regulation of food intake, it is not fruitful to search for precise regions entirely responsible for ‘hunger’ and ‘satiety’.