Perifornical fiber system mediates VMH electrically-induced suppression of feeding.

Fiber pathways mediating the cessation of food ingestion during continuous low-level electrical stimulation of the ventromedial region of the hypothalamus (VMH) were appraised in food-deprived male rats using knife cuts. Parasagittal knife cuts in the medial perifornical area of the hypothalamus produced much larger increases in threshold current intensities for the inhibition of feeding than did cuts in the lateral perifornical hypothalamus. These findings indicate that fiber pathways critical to the inhibitory feeding effect of continuous VMH electrical stimulation traverse the perifornical hypothalamus but not the lateral hypothalamus. A comparison of these and other results demonstrates an anatomical similarity between the fiber pathways mediating VMH electrically-induced inhibition of feeding and hypothalamic hyperphagia following lesions or knife cuts. The nature of the inhibitory feeding effect of VMH electrical stimulation is also addressed and behavioral observations strongly supportive of a specific anorectic effect produced by the stimulation are reported.