Selective blockade of hypothalamic hyperphagia and obesity in rats by serotonin-depleting midbrain lesions.

Adult female rats, depleted of 70 percent of forebrain serotonin by dorsal and median raphe lesions, showed little overeating of food pellets and obesity following medial hypothalamic lesions. However, these rats showed the same reduced acceptance of sucrose solutions, enhanced rejection of quinine solutions, and exaggerated weight gain on a high-fat diet as did other rats made obese by medial hypothalamic lesions alone. Since raphe lesions alone produced none of these effects, the pattern of behaviors observed suggests a hitherto unknown (perhaps secondary) role for brain serotonin metabolism in selective aspects of the medial hypothalamic syndrome.