Parabrachial nuclear complex in the rat (nuclei parabrachiales and nucleus Koelliker-Fuse). Detailed cytoarchitectonic division and connections compared.

Cresyl violet- and thionin-stained sections of the rat brain stem were used to study the cytoarchitectonics of the parabrachial nuclear complex consisting of nuclei parabrachiales and ncl. Koelliker-Fuse. As suggested by comparisons of the cytoarchitectonic structure and connections, the parabrachial nuclei can be divided into the following independent subnuclei: dorsalis (D), dorsomedialis (DM), dorsolateralis (DL), interstitialis (I), lateralis (L), ventralis (Ve) and medialis (M). According to conventional nomenclature, D, DM, DL, I and L are parts of ncl. parabrachialis lateralis (or dorsalis), while M and Ve belong in the ncl. parabrachialis medialis (or ventralis). Cytoarchitectonically, the Koelliker-Fuse nucleus can be divided into the pars oralis and pars caudalis. The cytoarchitectonic division and the position of afferent cells for specific target structures are in very good agreement while permitting comparisons of experimental findings in different animals with differently formed subnuclei. In the Discussion section, the hitherto known connections of the parabrachial nuclei complex are cross-referred to the relevant subnuclei.