title: The maintenance and termination of maternal behavior in rabbits: involvement of suckling and progesterone.
abstract: Rabbits mated at postpartum estrus become concurrently pregnant and lactating. They wean the first litter shortly before delivering the second one. Lactating-only rabbits do not spontaneously wean their young. These differences suggest that: a) suckling contributes to the long-term maintenance of maternal responsiveness and b) pregnancy-associated factors are essential to promote weaning. To explore if suckling stimulation interacts with the pregnancy condition we compared the behavior of intact and thelectomized (thelx; nipple-removed) rabbits, mated or not at postpartum estrus (Experiment 1). All lactating-only rabbits still showed nursing behavior by postpartum day 44; only 71% of thelx not pregnant does displayed maternal responsiveness for 31days and none by postpartum day 44. If mated at postpartum estrus maternal responsiveness was observed only in 25% of pregnant-lactating does on postpartum day 29 and in 8% of thelx-pregnant rabbits on postpartum day 26. As in pregnant-lactating does progesterone (P) is present across ca. 3weeks and then declines, but it is absent in lactating-only rabbits, in Experiment 2 we explored the effect of injecting P to lactating-only animals on their maternal responsiveness and milk output. P injections (20mg/day) were given across lactation days 1-30 or 1-23. Neither treatment modified maternal behavior: nearly all females entered the nest box, crouched over the litter and suckled it for ca. 3min, as did oil-injected nursing rabbits. In contrast, both P treatments accentuated the decline in milk output, with respect to oil-treated does. Results suggest that suckling promotes the long-term maintenance of maternal behavior while pregnancy-associated factors (not P) are essential to trigger weaning.
authors.affiliation: Centro de Investigación en Reproducción Animal, CINVESTAV-Universidad Autónoma, de Tlaxcala, Mexico. Electronic address: gabygmm@gmail.com.
authors.forename: Gabriela
authors.initials: G
authors.lastname: González-Mariscal
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Gallegos
mesh_terms: D000818:Animals; D005260:Female; D007774:Lactation / Q000187:drug effects / Q000502:physiology*; D008425:Maternal Behavior / Q000187:drug effects / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology / Q000523:psychology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000494:pharmacology*; D011817:Rabbits; D014886:Weaning
chemical_list: D011374:Progesterone
keywords: Lactation; Mammary gland; Oxytocin; Prolactin; Uterus; Weaning