Hypermetabolism of paraventricular hypothalamus in the congenitally helpless rat

The congenitally helpless rat, selectively bred to model behavioral features of depression, has shown metabolic activity patterns in frontal and cingulate cortex similar to those detected in human imaging studies of depression and sadness. This study extends the same metabolic mapping technique (quantitative cytochrome oxidase histochemistry) to the hypothalamus, where activity levels were assessed in six nuclei: paraventricular nucleus, medial preoptic area, lateral hypothalamic area, supraoptic nucleus, suprachiasmatic nucleus, and ventromedial nucleus. Helpless rats were compared with a strain of non-helpless rats selectively bred for stress resistance. Only the paraventricular nucleus showed a significant group difference, with helpless rats showing elevated metabolism and non-helpless rats showing reduced metabolism relative to normal rats. Thus, paraventricular nucleus activity may be associated with genetic susceptibility to helpless behavior.