Vestibular efferent neurons and catecholamine cell groups in the reticular formation of the pigeon

This study was designed to investigate the relationship between vestibular efferent neurons and catecholamine cell groups within the reticular formation of the pigeon. Horseradish peroxidase (HRP) was injected into the endolymphatic space of one labyrinth. The brain was perfused with glyoxylic acid and serial sections were examined with a fluorescence microscope. After documentation of the location of fluorescent cells the sections were reacted for HRP with tetramethylbenzidine. Fluorescent cells were noted intermingled among the HRP-labeled vestibular efferent neurons in the nucleus reticularis pontis caudalis. No neurons were both fluorescent and HRP-positive. Fluorescent cells were also noted bilaterally in locus ceruleus, raphe nucleus, and in close proximity to the abducent, facial, hypoglossal and ambiguus nuclei.