Growth Following Hypothalamic Lesions in the Weanling Rat1

Abstract

To investigate further the effect of hypothalamic ablation on growth, bilateral electrolytic lesions were made in 6 regions of the hypothalamus of male and female weanling rats which were observed until 97 days of age. Although sham-operated controls did not show significant reduction of growth, 5 of the hypothalamic groups showed a significant reduction of ponderal growth and 4 of linear growth; but some of the groups were small in number and the effects were less significant in the female. In some groups food intake and temperature regulation were altered, but in none was the resting oxygen consumption significantly changed. The effect of the lesions on the endocrines varied with location and sex. The most effective lesions for reduction of somatic growth in both sexes were in the region of the supraoptic nucleus, where thyrotrophic regulation may be impaired, and in the posteromedial region of the hypothalamus. The evidence suggests that ablation in some regions of the hypothalamus impairs growth by interfering with the fine regulation of endocrine function important to growth, while in other regions the primary effect may be on the regulation of energy exchange.