Abstract
(1) Centrally acting substances which have been found to facilitate feeding are norepinephrine, dopamine, acetylcholine, endorphins and benzodiazepine receptor ligands. (2) Those which have been found to inhibit feeding include norepinephrine, acetylcholine, serotonin, GABA, glycine, alanine, glutamine and several polypeptides which have recently been found to reside in the brain. (3) The specific behavioral functions of these various factors have not been identified. (4) The major endocrine effects on feeding are generally a facilitation of food intake by anabolic hormones and a reduction of food intake by catabolic hormones. (5) Whether central neurohumoral feeding effects are controlled by endocrine changes is not known except for the fact that norepinephrine-induced feeding requires an intact pituitary. (6) Hypothalamic lesions which modify feeding may operate partially through hormonal changes. For example, medial hypothalamic lesions may induce overeating via hyperinsulinemia, and part of the aphagia produced by lateral hypothalamic lesions may be a shift in body metabolism to catabolic endocrine patterns. (7) Appetite disorders such as ‘anorexia nervosa’ and the Kleine-Levin syndrome may be precipitated by imbalanced activity in medial and lateral hypothalamic circuitry which may result from aberrent sensitivities to sex steroids. (8) The extensive empirical findings in this area have not yet led to a coherent theory.