Figure 1 - Cytodendroarchitecture of the rat ambiguus complex.

Immunohistochemical staining for heat shock protein 27 (HSP27, panel a) reveals contiguous columns of motoneurons that line up in an oblique sagittal plane spanning the length of the ventral rhombencephalon (photomicrograph courtesy of Dr. D.A. Hopkins). The serial reconstruction (b) shows the same neuronal groupings after retrograde labeling with horse radish peroxidase HRP. Three main divisions are recognizable: a rostral compact formation of esophagomotor neurons (AMB-c), a caudal loose formation (AMB-l) of laryngomotor neurons, and an interposed semicompact formation of chiefly pharyngomotor neurons. The AMB-sc column continues into the rostral tip of the ambiguus complex overlying the facial motor nucleus (VIIm). Note dendritic radiations and bundling. Additional ventral most cell groups (b) represent the AMB external formation of vagal preganglionic neurons. (Source: Adapted from Bieger and Hopkins,¹⁸ with permission of J. Wiley & Sons.)