Distribution of beta-endorphin-like-immunoreactive structures in the chicken and quail brain as demonstrated with a new homologous antibody directed against a synthetic peptide.

A polyclonal rabbit antibody was raised against a synthetic peptide fragment located at the C-terminal end of turkey beta-endorphin (beta-END) and used to analyze the distribution of beta-END-immunoreactive-like structures in the quail and chicken brain. Three major groups of immunopositive cells were detected in the preoptic area-hypothalamus complex. A thin layer of immunopositive cells was parallel and adjacent to the ventral edge of the brain in the preoptic and anterior hypothalamic region, a more numerous group of immunoreactive perikarya was located along the walls of the third ventricle in these same regions, and, finally, a few scattered cells were found in a more lateral position on both the internal and external sides of the tip of the fasciculus prosencephali lateralis. The periventricular cell population extended in the caudal direction until the posterior hypothalamus. Labelled fibers were always associated with these immunoreactive perikarya, and they were also found in the adjacent hypothalamic regions. A dense innervation of the median eminence was also detected. These data are compared with previous studies in mammals and birds that had identified more restricted populations of immunoreactive cells and the possible sources of the observed discrepancy are discussed. The functional significance of the present data is also briefly analyzed.