Fos-like immunoreactivity in forebrain regions following self-stimulation of the lateral hypothalamus and the ventral tegmental area

Abstract

According to the descending-path hypothesis, the direct excitation of descending fibers linking the lateral hypothalamus (LH) and ventral tegmental area (VTA) contributes to the rewarding effect produced by electrical stimulation of the medial forebrain bundle (MFB). To visualize forebrain neurons activated by stimulation of both the LH and VTA, Fos-like immunoreactivity (FLIR) in forebrain regions was assessed following self-stimulation of these two sites in male rats. Among the regions where FLIR was greater in the stimulated hemisphere following either LH or VTA stimulation were the anterior LH, the substantia innominata, and the bed nucleus of the stria terminalis, and olfactory tubercle. These findings are analyzed with reference to the effects of forebrain lesions on self-stimulation of the MFB. Advantages and limitations of using FLIR to identify neurons activated by rewarding stimulation are discussed.