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Volume 16, Number 22, Issue of November 15, 1996 pp. 7347-7352
Copyright ©1996 Society for NeuroscienceIntrahypothalamic Implantation of Progesterone in Castrated Male Whiptail Lizards (Cnemidophorus inornatus) Elicits Courtship and Copulatory Behavior and Affects Androgen Receptor- and Progesterone Receptor-mRNA Expression in the Brain
Received July 9, 1996; revised Aug. 29, 1996; accepted Aug. 30, 1996.
David Crews, John Godwin, Vesta Hartman, Michael Grammer, Ellen A. Prediger, and Rebecca Sheppherd Department of Zoology and Institute for Reproductive Biology, University of Texas, Austin, Texas 78712
A primary tenet of behavioral neuroendocrinology is that gonadal steroid hormones act on limbic nuclei to activate mating behavior in vertebrates. Traditionally, research has focused on the regulation of male-typical sexual behavior by testicular androgens and female-typical sexual behavior by ovarian estrogen and progesterone. Indeed, progesterone generally is regarded as an antiandrogen, acting centrally to inhibit sexual behavior in males. However, experiments with lizards, and more recently with rats, have challenged this paradigm. For example, exogenous progesterone induces mating behavior in some, but not all, castrated male whiptail lizards. The present study determined that implantation of progesterone into the anterior hypothalamus preoptic area of castrated, progesterone-sensitive males completely restored sexual behavior but failed to elicit sexual activity in castrated, progesterone-insensitive males. Further, androgen receptor- and progesterone receptor-mRNA expression in specific brain regions was significantly different in progesterone-sensitive versus progesterone-insensitive animals. Progesterone-sensitive males showed significantly higher relative abundance of androgen receptor-mRNA in the preoptic area, amygdala, and lateral septum, as compared with progesterone-insensitive animals receiving the same treatment. In contrast, progesterone receptor-mRNA abundance was lower in preoptic area of progesterone-sensitive males than in progesterone-insensitive males. No differences were found in the baseline abundance of androgen receptor- or progesterone receptor-mRNA in these nuclei between control groups of progesterone-sensitive and progesterone-insensitive males who were castrated but not implanted. This suggests that progesterone differentially regulates its own receptor as well as androgen receptor in areas of the brain involved in the control of sexual behavior of males and that the nature of this regulation shows individual variability.
Key words: steroid hormone receptor; gene expression; intrahypothalamic implantation; septum; amygdala; preoptic area; sexual behavior; autoregulation; androgen; progesterone; reptile; lizard; male
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