Development of maternal behavior in nulliparous rats (Rattus norvegicus): Effects of sex and early maternal experience.

Abstract

Weanling female and male rats were exposed to either pups or pup-sized toys for 10 days beginning at 22 days of age in order to assess differences between pup-directed and toy-directed behaviors and to determine whether exposure to pups at this time increases susceptibility to maternal sensitization in adulthood. Adult sensitization involved exposing each subject to pups for 10 days beginning at 78 days of age. The principal results were as follows: (a) Weanlings retrieved, licked, and lay over pups, but not toys, and chewed on toys, but not pups, (b) Weanling males snowed more pup retrieval than weanling females, (c) Females and males preexposed to pups during "weanlinghood" showed more retrieval and licking of pups in adulthood than those not preexposed to pups, (d) Adult females were more fully maternal or nonmaternal than were adult males or weanlings of either sex, as indicated by their lower "partial retrieval" and "inconsistent retrieval" scores, their tendency to retrieve rapidly or not at all, and their greater correlation between retrieval and nest construction.

How early maternal separation and juvenile experience with pups affect maternal behavior and emotionality in adult postpartum rats

“…Juvenile animals, when exposed to neonatal pups, will also demonstrate maternal behaviors (Gray & Chesley, 1984). Although displaying many of the maternal behaviors, juveniles do not consistently display the fully integrated pattern of adultlike maternal behavior (Brunelli, Shindledecker, & Hofer, 1985).…”

“…Although displaying many of the maternal behaviors, juveniles do not consistently display the fully integrated pattern of adultlike maternal behavior (Brunelli, Shindledecker, & Hofer, 1985). Instead, the behavior toward foster pups is intermixed with play behaviors (Brunelli et al, 1985), although the play and maternal behaviors can be differentiated from each other by the differences shown by juveniles in their responses to pups versus toys (Gray & Chesley, 1984). Potentially, the enhancement of adult maternal behavior through experience with pups as a juvenile may be dependent on whether full maternal behavior-that is, retrieval of foster pups-is displayed during the juvenile experience.…”

Comparison of the “Nursing” and Other Parental Behaviors of Nulliparous and Lactating Female Rats

“…It is unlikely that feral virgin female rats would have either no experience with young pups until adulthood (Calhoun, 1963;Davis and Hall, 1951;Gilbert, Burgoon, Sullivan, and Adler, 1983;Gray and Chesley, 1984;Stern and Rogers, 1988) or repeated access as adults to another female's litter (Calhoun, 1963). The sensitization paradigm is therefore an unnatural, but potentially useful, model to examine nonhormonal factors regulating maternal behavior.…”

Cocaine disrupts pup-induced maternal behavior in juvenile and adult rats

“…Chronic cocaine and CS dams received subcutaneous (sc) injections twice daily throughout gestation (GD 1-20) on alternating flanks, of 15 mg/kg cocaine HCL (dose calculated as the free base; Sigma Chemical Company, St. Louis, MO) dissolved in 0.9% normal saline (total volume 2 ml/kg), or normal saline (0.9%) respectively, at approximately 0800 and 1600. Intermittent cocaine-treated dams received the same dose and volume of cocaine as the CC dams, except that their injections only occurred on two consecutive days, every five days during gestation (GD 2,3,8,9,14,15,20) and on the same respective days during the postpartum period. Intermittent saline-treated dams received normal saline (0.9%) on the same injection schedule as the IC dams.…”

“…Though the intact medial preoptic area (MPOA) is essential for postpartum and pup-induced maternal behavior in adult rats [13,41,43], large lesions of the MPOA in adolescents impair retrieval and nest-building behaviors only, rather than all elements of maternal behavior and gender does not seem to play as important a role [24]. Whereas adult females typically exhibit pup-induced maternal behavior faster than adult males, the reverse is true in juveniles, with males typically taking fewer days to exhibit pup-induced maternal behavior compared to females and juveniles of both sexes generally perform it several days faster than adults [2][3][4]14,23,30,45,54].…”