The cytoarchitecture of the adult human parabrachial nucleus: a Nissl and Golgi study

The parabrachial nucleus (PBN) plays important roles in numerous autonomic functions and in pain modulation. In different animal species, three main regions of the PBN have been identified: the m-PB, the 1-PB, and the Kölliker-Fuse nucleus (KF). The KF has not been identified in humans. The present study used Nissl and Golgi-Cox material and morphoquantitative methods to investigate the cytoarchitectural organization of the adult human PBN, paying particular attention to neuronal features endowed with functional significance, i.e. the arborization of the neurons. The PBN neuron population is made up of elements which are heterogeneous in size, shape and dendritic arborization, and grouped into two regions, the lateral and medial PBN (1- and m-PB). It has been suggested that some large sized neurons located in the ventral region of the m-PB might be the counterpart of the KF. In the m-PB the fusiform neurons are the most numerous cells; in the 1-PB the multipolar neurons prevail, and are particularly numerous in the dorsal 1-PB. Since the dendritic arborization is generally the main target of afferent projections to a neuron, it is possible that the 1-PB, and in particular its dorsal region, might be the main site for the endings of afferences to the human PBN.