Self-stimulation of the habenular complex in the rat.

The rewarding effect of habenular stimulation was studied in 65 rats. The animals learned to bar press for electrical stimulation of the medial or lateral habenular nucleus or the fasciculus retroflexus, but not the surrounding thalamic nuclei. The response rates were moderate and steady and not influenced by food or water deprivation. Habenular self-stimulation was significantly facilitated by placing lesions in the ipsilateral anterior part of the medial forebrain bundle (MFB). Similarly, MFB self-stimulation was enhanced by ipsilateral habenular lesions. Lesions centered in the region of median raphe nucleus suppressed habenular self-stimulation for more than 4 wk. Self-stimulation of median raphe was not affected by habenular lesions. The results show that habenular stimulation can produce a rewarding effect by exciting neurons in the region of the raphe nuclei but apparently without requiring the participation of the well-known MFB reward system.