Behavioral changes following VMH lesions in rats with controlled insulin levels

Abstract

The effects of ventromedial hypothalamic (VMH) lesions were studied in female rats made diabetic with streptozotocin that were given twice daily injections of protamine zinc insulin (0.75 μ/100g/day) and in non-diabetic animals of the same sex. Hyperphagia resulted from VMH lesions in both diabetic animals whose insulin levels were controlled and in non-diabetic animals. All animals with lesions exhibited persistent increases in feeding during the light protion of the light—dark cycle. Significant increases in body weight gain were observed in both diabetic and non-diabetic lesioned animals, but the magnitude of weight gain was greater after VMH lesions in non-diabetic rats. VMH lesions also reduced wood-gnawing and increased emotinality, aversion to quinine and reactivity to electric shock. None of the behavioral changes were dependent on hyperinsulinemia, although hyperinsulinemia may contribute to the magnitude of certain of these effects.