Multiple knife cuts between the medial and lateral hypothalamus in the rat: a reevaluation of hypothalamic feeding circuitry.

Single or multiple sets of bilateral knife cuts were made in female rats just lateral to the ventromedial hypothalamus (VMH) and/or just medial to the lateral hypothalamus (LH). The lateral VMH cuts by themselves produced greater hyperphagia and obesity than did the medial LH cuts. The lateral VMH knife cuts also significantly increased food intake and body weight in rats previously given bilateral cuts along the medial LH border. These findings indicate that the feeding inhibitory fibers responsible for the hyperphagia syndrome do not project from the VMH to the LH, and this calls for a reevaluation of hypothalamic circuitry. It was also discovered that sham surgery has a significant suppressive effect on the hyperphagia syndrome produced by hypothalamic knife cuts.