Production of the weanling rat dorsomedial hypothalamic syndrome by cathodal electrolytic lesion current.

Weanling male Sprague-Dawley rats received bilateral electrolytic lesions in the dorsomedial hypothalamic area by means of a direct cathodal current. Sham-operated rats served as controls. Ponderal and linear growth, obesity index, food intake, and several indices of intermediary metabolism of adipose tissue and muscle were measured. Cathodal lesions, as did anodal lesions reported on previously resulted in retardation of body weight, length, and food intake, while the obesity index remained in the normal range. Similarly, the metabolic data in adipose tissue and muscle are comparable to those from experiments in which dorsomedial lesions were placed by anodal current: incorporation of glucose into CO2 lipid, and glycogen of muscle tissue (diaphragm) were similar in DMN-lesioned rats and controls. The difference between anodal and cathodal lesions in this hypothalamic syndrome is a delay in the onset of hypophagia until about 30 days after the hypothalamic operation. The data support the concept that lesions in the hypothalamus, in general, exert their effect by destruction of neuronal assemblies, i.e., nerve cells and/or fiber tracts passing through the lesioned area.