- Are immediate early genes involved in gonadotropin-releasing hormone receptor gene regulation? Characterization of changes in GnRH receptor (GnRH-R), c-fos, and c-jun messenger ribonucleic acids during the ovine estrous cycle. Padmanabhan, V., Dalkin, A., Yasin, M., Haisenleder, D.J., Marshall, J.C., Landefeld, T.D. Biol. Reprod. (1995)