T644. USE OF A Y-MAZE TO ASSESS PARTNER PREFERENCE IN FEMALE GOATS. Margiasso, Mary¹, Katz, Larry ¹, ¹ Rutgers University, New Brunswick, NJ

W645. CORTISOL DELAYS THE ESTRADIOL-INDUCED LH SURGE: IS THIS DEPENDENT ON PRIOR OVARIAN STEROID EXPOSURE? Wagenmaker, Elizabeth¹, Breen, Kellie¹, Clarke, Iain², Oakley, Amy¹, Tilbrook, Alan³, Turner, Anne³, Karsch, Fred¹, ¹ University of Michigan, Ann Arbor, MI² Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia³ Monash University, Clayton, Victoria, Australia

M646. SERUM INHIBIN-A LEVELS IN ESTROGEN RECEPTOR-NULL MICE ARE INCREASED IN FEMALES LACKING ESTROGEN RECEPTOR-ALPHA BUT NOT ESTROGEN RECEPTOR-BETA. Jayes, Friederike C¹, Couse, John¹, Emmen, Judith M¹, Korach, Kenneth¹, ¹ National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC

T647. STIMULATING EFFECT OF WHITEFISH GnRH ON GONADOTROPIN RELEASE IN RUMINANTS. Kadokawa, Hiroya¹, ¹ National Institute of Livestock and Grassland Science, Nasushiobara, Japan

W648. DOES A TYPE II GLUCOCORTICOID RECEPTOR AGONIST INHIBIT PITUITARY RESPONSIVENESS TO GnRH? Case, Lisa¹, Breen, Kellie¹, Wagenmaker, Elizabeth¹, Young, Elizabeth¹, Karsch, Fred¹, ¹ University of Michigan, Ann Arbor, MI

M649. ESTROGEN RECEPTOR ALPHA AND BETA AGONIST INCREASE GnRH RECEPTOR NUMBER IN CULTURED OVINE PITUITARY CELLS. Davis, Tracy¹, Nett, Terry¹, ¹ Colorado State University, Fort Collins, CO

T650. MORPHOLOGICAL STUDY OF GONADOTROPIN-SECRETING CELLS IN OVARIECTOMIZED RATS TREATED WITH DIFFERENT ESTROGEN RECEPTOR (ER) LIGANDS: A ROLE FOR ER IN THE GONADOTROPE? Sanchez-Criado, Jose¹, Martin de las Mulas, Juana¹, Navarro, Victor¹, Bellido, Carmen¹, Aguilar, Rafaela¹, Garrido-Gracia, Jose¹, Tena-Sempere, Manuel¹, Blanco, Alfonso¹, ¹ University of Cordoba, Cordoba, Spain

W651. DIFFERENTIAL EFFECTS OF UNILATERAL HEMIOVARIECTOMY PERFORMED DURING ESTROUS CYCLE, ON TESTOSTERONE (T) SERUM LEVELS. Dominguez, Roberto¹, Rodriguez, Jorge¹, Cruz, María¹, Flores, Angelica¹, ¹ FES Zaragoza UNAM, Biology of Reproduction Research Unit, Mexico City, DF, Mexico

M652. ESTRADIOL INITIATES AND PROGESTERONE SUSTAINS THE DROP IN VAGINAL IMPEDANCE AT ESTRUS IN OVARIECTOMIZED GOATS. Imwalle, Bradley¹, Lehrer, Rami², Katz, Larry¹, ¹ Rutgers University, New Brunswick, NJ² Institute of Animal Science, The Volcani Center, Bet-Dagan, Israel

T653. FEEDING MELENGESTROL ACETATE (MGA) TO BULLS DURING THE PERI OR PRE-PUBERTAL PERIOD INDUCES DIFFERENCES IN ENDOCRINE PROFILES WHICH MAY LEAD TO ALTERATIONS IN TESTIS SIZE. Tepfer, April¹, McFee, Ryann¹, Bott, Rebecca¹, Clopton, Debra¹, Schulz, Joseph¹, Cupp, Andrea¹, ¹ University of Nebraska - Lincoln, Lincoln, NE

W654. EFFECTS OF CHOLINERGIC SYSTEM BLOCKADE ON THE mRNA EXPRESSION OF GnRH IN BOTH SIDES OF THE PREOPTIC AND ANTERIOR HYPOTHALAMIC AREA OF CYCLIC FEMALE RATS. Arteaga-Lopez, Paola¹, Dominguez, Roberto¹, Cerbon, Marco², Arrieta, Isabel ², Mendoza-Rodriguez, Carmen², Cruz, María ¹, ¹ FES Zaragoza UNAM, Biology of Reproduction Research Unit, Mexico City, DF, México² Facultad de Química UNAM, Mexico City, DF, Mexico

M655. MALE-INDUCED RISE IN PROGESTERONE PRECEDES RECEPTIVITY AND OVULATION IN THE GRAY SHORT-TAILED OPOSSUM (Monodelphis domestica). Harder, John¹, Tadros, Lisa¹, Rogier, Yimei¹, Norfolk, Jennifer¹, Fadem, Barbara², ¹ The Ohio State University, Columbus, OH² University of Medicine and Dentistry of New Jersey, Newark, NJ

T656. USE OF A Y-MAZE TO ASSESS PARTNER PREFERENCE IN MALE GOATS. Sweeney, Andrea¹, Katz, Larry¹, ¹ Rutgers University, New Brunswick, NJ

W657. PITUITARY FUNCTION IN YOUNG AND AGING FEMALE GROWTH HORMONE RECEPTOR GENE DISRUPTED MICE. Chandrashekar, Varadaraj¹, Abaonza, Kristin¹, Chinwokwu, Olatubosun¹, Bartke, Andrzej^{1, 2}, ¹ Southern Illinois University School of Medicine, Department of Physiology, Carbondale, IL² Southern Illinois University School of Medicine, Internal Medicine, Springfield, IL

M658. LIFESTYLE AND HORMONE DYNAMIC INDICES: FREE TESTOSTERONE DYNAMIC INDEX INCREASES ON A HIGH FAT DIET AND DECREASES WITH AEROBIC EXERCISE. Wynne-Edwards, Katherine¹, Hicks, Kristin¹, Lazier, Joanna¹, ¹ Queen's University, Kingston, ON, Canada

T659. GnRH NEURONS CONTACTING CEREBROSPINAL FLUID IN ESTROUS EWES. Billings, Heather¹, Lehman, Michael¹, Goodman, Robert², Amstalden, Marcel¹, McManus, Christina², Hileman, Stanley², ¹ University of Cincinnati, Cincinnati, OH² West Virginia University, Morgantown, WV

W660. FETAL PROGRAMMING OF THE POSTNATAL RESPONSIVENESS OF LH TO ESTRADIOL NEGATIVE FEEDBACK IN SHEEP: TIME AND DURATION OF EXPOSURE AND QUALITY OF PRENATAL STEROID. Lee, James¹, Aizenburg, Esther¹, Djoumbi, Danielle¹, Forster, Douglas¹, Padmanabhan, Vasantha¹, ¹ University of Michigan, Ann Arbor, MI

M661. DEVELOPMENTAL EXPOSURE TO ENVIRONMENTAL ESTROGENS ALTERS ADULT BEHAVIOR AND PHYSIOLOGY IN THE RAT. Ryan, Bryce¹, Gray, L Earl², Crofton, Kevin², Vandenbergh, John ¹, ¹ North Carolina State University, Raleigh, NC² US Environmental Protection Agency, Research Triangle Park, NC

T662. PROGESTERONE RECEPTOR IMMUNOREACTIVITY IN BRAINS OF GRAY SHORT-TAILED OPOSSUMS DURING PHEROMONAL INDUCTION OF ESTRUS. Vitazka, Maria¹, Norfolk, Jennifer¹, Cardenas, Horacio ¹, Cruz, Yolanda², Fadem, Barbara³, Harder, John¹, ¹ The Ohio State University, Columbus, OH² Oberlin College, Oberlin, OH³ University of Medicine and Dentistry of New Jersey, Newark, NJ