NEUROPEPTIDE TYROSINE IN THE BRAIN OF THE AFRICAN LUNGFISH, PROTOPTERUS ANNECTENS - IMMUNOHISTOCHEMICAL LOCALIZATION AND BIOCHEMICAL-CHARACTERIZATION

Lungfishes, which share similarities with both fishes and amphibians, represent an interesting group in which to investigate the evolutionar y transition from fishes to tetrapods. In the present study, we have i nvestigated the localization and biochemical characteristics of neurop eptide Y (NPY)-immunoreactive material in the central nervous system o f the African lungfish, Protopterus annectens. NPY-immunoreactive cell bodies were found in various regions of the brain, most notably in th e telencephalon (septal area, ventral striatum, and nucleus accumbens) , in the diencephalon (preoptic nucleus, periventricular region of the hypothalamus, and ventral thalamus), and in the tegmentum of the mese ncephalon. A strong immunoreaction was also detected in cell bodies of the nerves terminalis. Immunoreactive nerve fibers were particularly abundant in the ventral striatum, the nucleus accumbens, the diagonal band of Broca, the hypothalamus, and the mesencephalic tegmentum. Posi tive fibers were also seen in the median eminence and in the neural lo be of the pituitary. The NPY-immunoreactive material localized in the brain and pituitary was characterized by combining high-performance li quid chromatography (HPLC) analysis and radioimmunological quantitatio n. The displacement curves obtained with synthetic porcine and frog NP Y and serial dilutions of brain and pituitary extracts were parallel. Reversed-phase HPLC analysis of telencephalon, diencephalon, and pitui tary extracts resolved a major NPY-immunoreactive peak that coeluted w ith frog NPY. The similarity between the distribution of NPY-containin g neurons and the biochemical characteristics of the immunoreactive pe ptide in the brain of lungfish and frog strongly favors a close phylog enetic relationship between dipnoans and amphibians. (C) 1995 Wiley-Li ss, Inc.