EXTENDED ABSTRACT ONLY – DO NOT CITE Lamprey Reproductive Physiology in Sea Lamprey

A key neuroendocrine function of the hypothalamus in the control of reproduction is the timed release of the decapeptide, GnRH, which acts on the pituitary to regulate the pituitary-gonadal axis for all vertebrates. Gonadotropins, secreted in response to GnRH, are released from the pituitary gland and are the major hormones influencing steroidogenesis and gametogenesis. Until about 18 years ago, there had been little evidence for brain control of reproduction in lampreys. However, we have made substantial progress in this area (See Reviews: Sower, 1998, 2002; Sower and Kawauchi, 2001). We now have established a well-defined neuroendocrine axis in lampreys. We identified and sequenced two molecular forms of GnRH in the sea lamprey: lamprey GnRH-I and lamprey GnRH-III. In addition, we have identified the cDNA of lamprey GnRH-I (Suzuki et al., 2000) and lamprey GnRH-III (Silver et al. 2001). Lampreys are the most primitive vertebrates for which there are demonstrated functional roles for multiple GnRH neurohormones involved in pituitary-reproductive activity. Both lamprey GnRH-I and-III have been show