Deep brain stimulation of the rostromedial tegmental nucleus: An unanticipated, selective effect on food intake.

The rostromedial tegmental nucleus (RMTg) is a relatively newly described brainstem structure. The RMTg is extensively connected to both dopaminergic (DA) and serotoninergic key areas and it fulfills a pivotal role in the regulation of mesolimbic and nigrostriatal DA release. The RMTg may directly influence DA- and 5-HT associated motor and possibly also mood related behavior, the latter of which has not yet been well described. The current study explored the consequences of RMTg manipulation on DA- and 5-HT related behavior through the application of RMTg deep brain stimulation (DBS) with both high and low frequency stimulation (LFS and HFS). We used a wide array of motor and mood tests to assess changes in behavior. RMTg DBS did not change behavioral outcomes in the Skinner box task, nor in the Catwalk, the sucrose intake test, the open field test, the elevated zero maze, or the place preference test, but LFS did induce a significant decrease in food intake. This seems to be a selective effect as no motor or anxiety changes were observed that could lead to attenuated food intake. This finding not only underlines the RMTg's braking effect on the VTA, but possibly also on the forebrain, where GABA-ergic RMTg efferent may cause suppression of feeding in the lateral hypothalamus.