Lateral hypothalamic lesions in ground squirrels: rapid recovery and residual deficits.

The effects of lateral hypothalamic (LH) lesions were studied in golden-mantled ground squirrels, Spermophilus lateralis, a species of mammalian hibernator that displays endogenous circannual body weight cycles when kept in constant conditions. The lesions were made during the weight-gain phase. Evidence that the lesions were well placed included interruption of weight gain, transient aphagia, disrupted nest building, increased spillage of food crumbs and in some cases abnormal postures or movement. Despite these deficits most animals survived. Their body weights at the first postoperative peak of the cycle recovered either to within the control range (Experiment 1) or close to preoperative peak levels (Experiment 2). There was no evidence that the lesions lowered set points. The rapid recovery of weight and eating by ground squirrels given only dry rodent chow, after large lesions (1.5-2.5 mA, DC anodal, 15-25 s), contrasts with what is seen in rats following LH lesions.