Postnatal experiences influence the behavior in adult male and female Fischer and Lewis rats

Abstract

The postnatal environment with the rat pups' dam as the most important regulator, plays a central role in determining developmental processes of the offspring. Early disturbances of the dam-pup-dyade, like separation from the dam for hours (maternal deprivation, MD), or a short period of separation, and exposure to novelty, like the handling stimulation (HA), might induce long-lasting changes within the individual. To further investigate the susceptibility to these postnatal manipulations with regard to both, sex and genetic background, we used male and female Fischer (F344) and Lewis (LEW) rats. F344 and LEW rats were daily subjected to either HA, MD, or were left undisturbed until weaning. The immediate effects of these manipulations were studied using the mother-pup-interaction-test on postnatal days 3-7. At the age of 4 months, animals were subjected to a behavioral test battery, determining activity, exploration, and anxiety-like behavioral parameters. Postnatal manipulations induced significant alterations of the mother-pup-interaction patterns that were more pronounced in F344 dams. MD and HA F344 dams were longer off pups than LEW dams. MD F344 pups were longer groomed than MD LEW pups and HA F344 pups were longer passive nursed than HA LEW pups. In adulthood, F344 rats showed increased anxiety-like behavior compared to LEW rats. Furthermore, females of both strains exhibited more anxiety-like behavior than males. Test independently, MD led to more anxiety-like behavior and less exploratory responses, while handled rats exhibited an anxiolytic-like behavior and increased exploratory responses. In conclusion, postnatal experiences specifically altered the behavioral phenotype in adulthood. While these changes were co-directional in the two strains and in both sexes, the degree of susceptibility varied.

The interaction of disrupted Type II Neuregulin 1 and chronic adolescent stress on adult anxiety- and fear-related behaviors

“…In control groups, disruption of Nrg1 resulted in a trend toward increased anxiety-like behavior in males and significantly decreased anxiety-like behavior in females compared to WT animals. These genotype differences resulted in opposite sex differences, with CON WT females exhibiting greater anxiety-like behavior than CON WT males, which is consistent with the findings of others in different assays of anxiety-like behavior in Fischer 344 rats (Skripuletz et al, 2010). On the other hand, in CON Nrg1 Tn animals, males demonstrated significantly greater anxiety-like behavior than females.…”

Parent behaviors moderate the relationship between neonatal pain and internalizing behaviors at 18 months corrected age in children born very prematurely

“…Our finding that parent sensitivity and nonhostility moderate the relationship between neonatal pain and internalizing behavior at 18 months CA in children born very preterm, is supported by animal models that have demonstrated mother-infant interactive behaviors can protect against effects of early stress on later behavior [16, 22]. It should be noted, however, that unlike animal models of early stress and behavior [7, 40, 62, 64], in the present study we did not find gender differences in behavior of children born very preterm or full-term. Offspring of low licking and grooming dams are fearful in response to novelty in adulthood [16].…”

Effects of cross-fostering on play and anxiety in juvenile Fischer 344 and Lewis rats

“…In addition to being consistently less playful than other strains, rats of the F344 strain are hyper-responsive to stress [20–24] and while some studies report the F344 strain to be more anxious than other strains [25–29] other studies have found the F344 strain to be either less anxious [30, 31] or to not differ in anxiety [60, 61]. Given this ambiguity and since these earlier studies assessed anxiety in adults, we considered the possibility that play in the juvenile F344 rat may be dampened due to enhanced anxiety in this strain.…”

“…In addition to being consistently less playful than other strains, rats of the F344 strain are also hyper-responsive to stress [20–24] and while some studies have reported higher levels of anxiety in F344 rats [25–29] others have reported F344 rats to be less anxious than other strains [30, 31]. In either case, given the extent to which anxiety and stress can negatively impact play in the rat [32] it is possible that play in the F344 rat may be dampened due to altered levels of anxiety in this strain.…”