[Organization of the pallidal projections of the rostromedial tegmental nucleus in the dog brain]

The method of retrograde and anterograde transport of horse-radish peroxidase was used to study the organization of the projections of the rostromedial tegmental nucleus (RMTN) to functionally distinct regions of pallidal structures of brain in dogs (n = 13). It was found that the fibers formed by the neurons of the limbic medial segments of RMTN rostral and caudal regions projected to the limbic pallidal regions--ventral globus pallidus and ventral pallidum. The reciprocal projections were detected between the ventral pallidum and medial segment of the rostral RMTN. These data indicate the possibility of the segregated conduction of the limbic information in the examined projection systems. However, in the majority of the pallidal structures, the convergence of the projection fibers originating from the neurons of functionally different parts of RMTN was observed. Thus, the projection fibers formed by the neurons of motor lateral and limbic medial parts of RMTN are directed to the limbic ventral segment of the globus pallidus and to the entopeduncular nucleus, which is innervated by the fibers formed by the neurons of functionally diverse structures. The possible pathways for conduction of functionally different information and its integration in the projection systems investigated are discussed.