Distribution pattern of tyrosine hydroxylase in the brain and pituitary of the lungfish Protopterus annectens.

The distribution of tyrosine hydroxylase (TH) was investigated in the brain and pituitary of the African lungfish Protopterus annectens by using immunohistochemistry. TH was expressed in the olfactory bulbs, pallium and subpallium, hypothalamus, tegmentum, reticular formation, nucleus of the solitary tract, and pituitary. In some cells of the hypothalamus and pituitary, TH is colocalized with vasoactive intestinal peptide. In the intermediate and neuronal lobes of the pituitary, TH is expressed in glial fibrillary acidic protein-contained cells. These data suggest that, in lungfish, catecholamine may play a role in olfaction information processing, regulation of visceral activities, and pituitary secretion.