Comparative cytoarchitectonics of the parabrachial nuclear complex in mammals

The cytoarchitectonics of the parabrachial nuclear complex (PBNC) were studied in brain stem sections, stained with cresyl violet, from laboratory and phylogenetically interesting mammals. In all the animals studied, the PBNC can be separated into the following subnuclei: dorsal (D), dorsomedial (DM), dorsolateral (DL), lateral (L), medial (M), ventral (Ve) and the less distinct interstitial subnucleus (I). According to the nomenclature used hitherto, D, DM, DL, I and L belong to the ncl. parabrachialis lateralis (or dorsalis) and M and Ve to the ncl. parabrachialis medialis (or ventralis). In most laboratory animals (rodents, the rabbit), the individual subnuclei are roughly all the same size. In other phylogenetically interesting mammals, however, the size of some subnuclei deviates from the laboratory animal "norm". A comparison among these animals shows that in higher primates three of the six parabrachial subnuclei are enlarged. In insectivores the subncl. lateralis and subncl. medialis are also enlarged--possibly as an expression of a definite phylogenetic trend. In the discussion, the previously known connections of the PBNC are included and it is shown that each subnucleus has its characteristic connections.