Immunohistochemical study of the distribution of vasotocin reacting neurons in avian diencephalon.

Vasotocin (VT)- and neurophysin (NPH)-containing neurons were immunocytochemically demonstrated in the diencephalon of the Japanese quail (Coturnix coturnix japonica), domestic fowl (Gallus gallus), and Pekin duck (Anas platyrhynchos). In these three avian species, the immunoreactive cells are similarly distributed into three different diencephalic regions: lateral (L), periventricular (P), and dorsal diencephalic (DD). A different number of cell clusters can be easily identified in each region according to its topographical location. Interspecific differences depend on the total number of immunoreactive cells, the cell sizes and the density in each cell cluster. Present results show that the nomenclature of the VT-system originally proposed for the pigeon can be easily applied to all the avian species so far topographically studied. The group nomenclature based only upon the location of immunoreactive elements may avoid potentially inaccurate mammalian homologies, and makes easier the comparison between studies performed in different birds.