Comparative anatomical study of the tegmentomammillary projections in some mammals: a horseradish peroxidase study.

Mammillary projections from each subnuclei of Gudden 's tegmental nuclei were investigated by retrograde transport of horseradish peroxidase (HRP) in the cat, rat, guinea pig, golden hamster and house shrew (Suncus murinus, Insectivora). The dorsal tegmental nucleus of Gudden (TD) is composed of the pars dorsalis (TDD) and the pars ventralis ( TDV ) in the cat, rat, guinea pig, and golden hamster, but the TD of the house shrew can not be divided. The ventral tegmental nucleus of Gudden (TV) is composed of the pars principalis (TVP) and the pars suprafascicularis ( TVS ) in the golden hamster and house shrew, but the TVS is not recognized in the cat, rat and guinea pig. The TDV projects to the lateral mammillary nucleus, and the TVP projects to the medial mammillary nucleus ipsilaterally in the cat, rat, guinea pig and golden hamster. The TVS of the golden hamster projects to the medial mammillary nucleus. The TVP and TVS of the house shrew project to the medial mammillary nucleus, and the TVS also to the lateral mammillary nucleus. In addition, the pars compacta of the nucleus centralis superior projects to the medial mammillary nucleus in the rat, guinea pig and golden hamster. However, the TDD sends no fibers to the mammillary nuclei in these 5 species of mammals.