Progesterone-facilitated lordosis in medial preoptic area-lesioned, juvenile guinea pigs.
Juvenile female guinea pigs rarely display lordosis in response to estradiol and progesterone treatments that elicit sexual receptivity in adults. To test the hypothesis that the medial preoptic area (MPOA) tonically inhibits the display of steroid-induced lordosis in juveniles, 11-day-old guinea pigs were ovariectomized (OVX) and received bilateral, sham, or electrolytic lesions aimed at the MPOA 3-4 days later. At 20-22 days of age, these females were tested for the expression of sexual receptivity following injections of estradiol benzoate (EB, 10 micrograms s.c.) and progesterone (0.5 mg s.c., 40 h after EB). The lesions damaged portions of the MPOA, the nucleus of the diagonal band of Broca, the lateral aspect of the medial preoptic nucleus, the medial part of the preventricular portion of the periventricular nucleus, and the anterior commissure. The lesions did not alter the display of estradiol-induced lordosis. However, after treatment with EB plus progesterone, 20% of the sham-lesioned females displayed lordosis, as compared to 80% of the MPOA-lesioned animals. These data are consistent with the hypothesis that neurons originating in and/or traversing the MPOA tonically suppress the display of progesterone-facilitated lordosis in juvenile guinea pigs. Removal of this inhibitory input allows prepubertal females to respond behaviorally to estradiol and progesterone in an adult-typical fashion.
Olster
D H
DH
Psychology Department, University of California, Santa Barbara 93106, USA.
D000818:Animals; D001931:Brain Mapping; D004958:Estradiol / Q000502:physiology*; D004971:Estrus / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D009433:Neural Inhibition / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology; D011301:Preoptic Area / Q000502:physiology*; D011374:Progesterone / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology*
D011374:Progesterone; D004958:Estradiol