Rewarding effectiveness of caudal MFB stimulation is unaltered following DMH lesions

The dorsomedial hypothalamus (DMH) has been proposed to be a major part of the neural substrate for self-stimulation of the medial forebrain bundle (MFB). In this report, rate-frequency and rate-current curves were collected from 19 rats with lesions in or around the DMH and stimulation electrodes in or near the caudal MFB. Thirteen rats with lesions of the DMH showed little or no postlesion change in the rewarding effectiveness of caudomedial MFB stimulation. Six other lesions, affecting the anterior, dorsal, and/or ventromedial hypothalamus, were also ineffective in changing rewarding effectiveness. The one lesion that was followed by a substantial decrease in rewarding effectiveness, invaded the medial MFB at the level of the lateral hypothalamus but produced little DMH damage. These data do not support the notion that neurons arising in, terminating in, or projecting through the DMH play an important role in MFB self-stimulation.