Distribution Analysis of the Two Chicken Estrogen Receptor-Alpha Isoforms and Their Transcripts in the Hypothalamus and Anterior Pituitary Gland

Abstract Estrogen plays a key role in the control of reproductive behavior and in the regulation of the neuroendocrine system. To elucidate the mechanisms by which it controls these functions it is important to understand how estrogenic effects are mediated. We have investigated the distribution of the two isoforms of the chicken estrogen receptor alpha (cER-α) protein; the previously characterized cER-α 66 and a new N-terminal truncated isoform, cER-α 61. Immunolocalization demonstrated the presence of cER-α 66 protein in hypothalamic areas, principally the nucleus septalis lateralis, bed nucleus striae terminalis medialis, nucleus preopticus medialis, and nucleus infundibuli hypothalami, and in the anterior pituitary gland. When the distribution of ER-α immunoreactive cells was compared using the antibodies H 222 (directed against the hormone-binding domain) and ER 221 (directed against the 21-amino acid N-terminus), no apparent differences could be detected. Because this immunocytochemical approach was...