The distribution of catecholamine (CA) containing neurons and nerve terminals in the brain stem from birds to teleosts were studied by means of histofluorescence technique of glyoxylic acid-formaldehyde combining method. The present study revealed that there exists marked differences in topography of CA neurons between higher vertebrates (birds and reptile) and lower vertebrates (amphibia and teleosts). Tegmental CA neurons in the birds and reptile are much more developed than those of amphibia and teleosts. Furthermore, huge collection of CA neurons (presumably dopamine) in the midbrain tegmentum could not be found in the amphibia and teleosts. On the other hand, distribution of CA nerve terminals in the brain stem is essentially similar throughout the vertebrate brains, though there exist modifications by secondary pattern distortions which correspond to various conditions of their lives. Some possible significance of CA neurons on development of central nervous system was discussed.
