Differences in maternal behavior of rats and the sociosexual development of the offspring

Abstract

This paper describes experiments designed to investigate long-term behavioral consequences for offspring of changes in maternal behavior directed toward them as pups. Specifically, the hypothesis was considered that experimentally induced alterations in maternal behavior would result in general and wide-ranging effects on offspring development, including effects on later social and sexual behavior. The first experiment looked at the effects of changing pup odors on maternal responsiveness toward the pups, and showed that the application of perfume, particularly to the anogenital region, resulted in significant lowering of maternal anogenital licking of pups. Non-pup-directed behavior did not differ between groups. The behavior of those pups that had thus differed in infant experience was then followed in three subsequent experiments. In Experiment 2, social behavior during the juvenile period was investigated, focusing particularly on the expression of social play. The most noticeable difference to emerge in this experiment was that male pups that had been anogenitally perfumed as infants showed much higher levels of social play than male or female pups from other treatment groups. The last two experiments considered adult behavior. Experiment 3 showed that there are no lasting effects of the neonatal treatment on the attractiveness an animal has for its conspecifics. In the final experiment, "masculine" sexual behavior of males (mounts with intromission), and "feminine" sexual behavior of females (i.e., lordosis and proceptive behavior) were investigated. This confirmed previous reports by Moore (1984) (Moore, C. L. (1984). Maternal contributions to the development of masculine sexual behavior in laboratory rats. Dev. Psychobiol., 17:347-363) that those male pups that had received lower rates of anogenital licking as pups showed longer intermount intervals, when tested as adults. The results are discussed in relation to the development of sexually differentiated behavior.

Variation in maternal care and individual differences in play, exploration, and grooming of juvenile Norway rat offspring

“…Similar results were previously obtained by lining the nasal passages with polyethylene tubing (Moore, 1984; a less satisfactory procedure because it can lead to secondary problems from blocked tubes), and by applying masking odors (perfumes) to the pups (Birke & Sadler, 1987;Moore, 1981). Although sharply reduced, AGL was not eliminated by zinc sulfate treatment in the present study.…”

“…The results obtained for rearing and defecation in the open field and for grooming behavior during the play sessions are consistent with these predictions. However, as noted by Birke and Sadler (1987) in their previous study, the results for play were contrary to predictions.…”

“…Although the details of the developmental pathways are not known, it has been established that when present, sex differences originate with perinatal androgen differences (Meaney & Stewart, 1981). Whatever the complete developmental explanation of sex differences in propensity to play, it is apparent from the present study and from the prior work of Birke and Sadler (1987) that the typical maternal bias in anogenital licking does not account for sex differences in play behavior.…”

The Meaning of Weaning: Influence of the Weaning Period on Behavioral Development in Mice

“…This behavior was observed most often immediately after pups would seek nipple contacts, would continue for several minutes during which time a female would switch her mounting between different pups. Though we were not able to discern whether male or female pups were mounted more frequently, this would certainly be interesting to investigate further given that other forms of tactile stimulation such as maternal LG have previously been demonstrated to be preferentially given to males in the latter periods of lactation and to perhaps lead to the development of sex differences in behavior [Birke and Sadler, 1987;Moore, 1984]. Given that female mounting behavior is often considered to be related to the establishment of dominant-subordinate relationships [Fang and Clemens, 1999], and that this behavior was observed immediately following nipple contact solicitations by pups, it appears as if maternal mounting may be an active component of the weaning process undertaken by the dams.…”

The influence of natural variations in maternal care on play fighting in the rat

“…Mothers whose pups were treated with either zinc sulfate, saline (Moore & Power, 1992) or perfume (Birke & Sadler, 1987) engage in significantly less AGL of pups. Interestingly, the reduced level of pup AGL is associated with increased play during the juvenile phase of development in males (Birke & Sadler, 1987;Moore & Power, 1992).…”