Catecholamine neurons in the brain stem of tree shrew (Tupaia)

Glyoxylic acid-paraformaldehyde-induced histofluorescence was used to determine locations of catecholamine-containing neurons in the brain stem of Tupaia. Fluorescent cells in the medulla were located ventrolaterally in association with the lateral reticular nucleus; another group was found dorsolateral to the hypoglossal nucleus and extended laterally toward the solitary nucleus. In the pons, fluorescent cells were found in locus coeruleus, subcoeruleus and in association with the superior olivary nucleus. At caudal midbrain levels, catecholamine neurons were seen within the reticular formation and in association with the dorsal raphe nucleus, while more rostrally fluorescent neurons were located in substantia nigra, ventral tegmental area, among root fibers of the oculomotor nerve and in periaqueductal gray. The locations of catecholamine-containing neurons in tree shrew conform to the general mammalian pattern. Additionally, tree shrew has catecholamine neurons in the rostral mesencephalic periaqueductal gray as described in rat, opossum, rabbit and some primate; catecholamine neurons are also associated with the dorsal raphe nucleus in Tupaia, a finding previously reported only in primates.