Development of steroid-induced lordosis in female guinea pigs: effects of different estradiol and progesterone treatments, clonidine, and early weaning.
The ability of developing ovariectomized (OVX) guinea pigs to display lordosis following a variety of steroid treatments which are behaviorally effective in adults was examined. Females OVX at 11 days of age did not display lordosis at 20 days of age, following treatment with several dose combinations of estradiol benzoate (EB, 10-50 micrograms) and progesterone (0.5-5 mg). By 30 days of age, 25% of the animals responded to EB plus progesterone, and by 40 days of age, adult-typical responses were observed. The developmental profile of responsiveness to steroids was not altered by varying the age at OVX, or by allowing pups to remain with a lactating mother. OVX females given estradiol (E2) implants did not exhibit progesterone-facilitated lordosis earlier than those treated with EB: however, the former group did show an unusually high incidence of progesterone-independent lordosis at 40 days of age. Twenty-day-old females also did not respond behaviorally to discrete pulses of E2 followed by progesterone, a treatment which was very effective in adults. Finally, lordosis was not facilitated in EB-primed, 20-day-old females by the alpha-noradrenergic agonist, clonidine, a treatment which was effective in adult females. These data illustrate a variety of conditions under which juvenile female guinea pigs do not exhibit steroid-induced lordosis. Since 20-day-old, EB-treated females also did not exhibit clonidine-facilitated lordosis, incomplete development of the central steroid-responsive and/or noradrenergic systems may contribute to the inability to display steroid-induced estrous behavior at this age.
Olster
D H
DH
Department of Psychology and Neuroscience, University of Massachusetts, Amherst 01003.
Blaustein
J D
JD
D000818:Animals; D000831:Animals, Newborn; D003000:Clonidine / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D011374:Progesterone / Q000494:pharmacology*; D011941:Receptors, Adrenergic / Q000187:drug effects; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D012741:Sexual Maturation / Q000187:drug effects*; D014886:Weaning
D011941:Receptors, Adrenergic; D011374:Progesterone; D004958:Estradiol; D003000:Clonidine