Gudden's tegmental nuclei and their connections to the hypothalamus and the reticular formation. I. An experimental study using retrograde labelling with HRP or iron-dextran in the rat.

31 rats were studied for the retrograde transport of HRP or dextran-fer from the corpus mamillare, anterior hypothalamus or reticular formation to the cells of the ventral (VG) and dorsal (DG) Gudden's tegmental nuclei. Judging by the position of the projection cells the VG was found divisible into the peripheral and central parts, a finding out of line with the conventional cytoarchitectonic division. The two parts differ in part of their projections. While both project jointly to the medial mamillary body, the peripheral part has a separate projection to the whole lateral hypothalamus whereas the central part projects also to the RF (ncl. pedunculopontinus and ncl. pontis oralis). The group of cells localized close to the cranial field of the VG, cytoarchitectonically referred to as the pars compacta ncl. centralis superioris, has the same projections as the external parts of the VG and can, therefore, be seen as a component of the VG peripheral part like the cells over the caudal field of the VG (pars intrafascucularis localized already among FLM fibres). The central part is made up of cells localized in the middle portions of the bulk of the VG cells. The dorsal Gudden's tegmental nucleus projects its ventral part to the lateral mamillary body, to the medial and lateral hypothalamus and to the RF (ncl. pontis oralis). The dorsal part of the DG projects solely to the RF (ncl. pontis oralis).