COMPARATIVE STUDY OF THE CITOARCHITECTURE AND NEUROCHEMICAL CONTENT OF AREA POSTREMA IN THREE SPECIES OF FISH: SALMO TRUTTA FARIO L., ACIPENSER BAERI BRANDT AND SCYLLIORHINUS CANICULA L.

Area postrema (AP) is a neurohemal organ located at the transition between rhombencephalon and spinal cord, whose structure and functions have been well studied in mammals but poorly known in fishes. In the present study we characterize the structure of AP in three species of fish, the brown trout (Salmo trutta fario L.), the Siberian sturgeon (Acipenser baeri Brandt) and the dogfish (Scyliorhinus canicula L.). Comparing the results obtained by using immunohistochemical techniques, we identified similarities, but also differences between the cytochemical structures of the AP in these three species. The cytoarchitecture is basically similar, all having the same stratified organization. The differences appeared in the neurochemical content of the neurons in this zone. It seems like evolution kept the basic structure but modified the neurotransmitters used by the cells and the fibers system.