FOS-LIKE IMMUNOREACTIVITY IN FOREBRAIN REGIONS FOLLOWING SELF-STIMULATION OF THE LATERAL HYPOTHALAMUS AND THE VENTRAL TEGMENTAL AREA

According to the descending-path hypothesis, the direct excitation of descending fibers linking the lateral hypothalamus (LH) and ventral te gmental area (VTA) contributes to the rewarding effect produced by ele ctrical stimulation of the medial forebrain bundle (MFB). To visualize forebrain neurons activated by stimulation of both the LH and VTA, Fo s-like immunoreactivity (FLIR) in forebrain regions was assessed follo wing self-stimulation of these two sites in male rats. Among the regio ns where FLIR was greater in the stimulated hemisphere following eithe r LH or VTA stimulation were the anterior LH, the substantia innominat a, and the bed nucleus of the stria terminalis, and olfactory tubercle . These findings are analyzed with reference to the effects of forebra in lesions on self-stimulation of the MFB. Advantages and limitations of using FLIR to identify neurons activated by rewarding stimulation a re discussed. (C) 1997 Elsevier Science B.V.