Abstract
The nature and extent of care received by an infant can affect social, emotional and cognitive development, features that endure into adulthood. Here we employed the monogamous, California mouse (Peromyscus californicus), a species, like the human, where both parents invest in offspring care, to determine whether early exposure to endocrine disrupting chemicals (EDC: bisphenol A, BPA; ethinyl estradiol, EE) of one or both parents altered their behaviors towards their pups. Females exposed to either compound spent less time nursing, grooming and being associated with their pups than controls, although there was little consequence on their weight gain. Care of pups by males was less affected by exposure to BPA and EE, but control, non-exposed females appeared able to “sense” a male partner previously exposed to either compound and, as a consequence, reduced their own parental investment in offspring from such pairings. The data emphasize the potential vulnerability of pups born to parents that had been exposed during their own early development to EDC, and that effects on the male, although subtle, also have consequences on overall parental care due to lack of full acceptance of the male by the female partner.
Highlights
Biparental care of offspring occurs in only a minority of mammals [1] and is generally encountered in species that are socially monogamous and where the male remains bonded to the female during the period in which the offspring are conceived, suckled and weaned [2]
Two weeks prior to breeding, virgin P0 females, 8 to 12 wks of age were randomly assigned to receive one of three diets: 1) a low phytoestrogen AIN 93G diet supplemented with 7% by wt corn oil to minimize potential phytoestrogenic contamination that would otherwise be present with inclusion of soybean oil in the diet, 2) this diet supplemented with 50 mg bisphenol A (BPA)/kg feed weight, which we have documented to lead to internal serum concentrations close to those measured in pregnant women unknowingly exposed to this chemical [21, 22], and 3) AIN93G diet supplemented with 0.1 parts per billion of ethinyl estradiol (EE), as the FDA required positive control for BPA studies [23]
When the animals reached adulthood (~90 days of age), males and females from each groups were randomly paired (4 to 7 pairs/combination) with either controls or breeding partners developmental exposed to the same endocrine disrupting chemicals (EDC) such that the pairings included controls, BPA-exposed females to control males (BPAF), control females bred to BPA-exposed males (BPAM), BPA-exposed females mated to a BPA-exposed males (BPAMF), EE-exposed females mated to control males (EEF), control females bred to EE-exposed males (EEM), and EE-exposed females mated to EE-exposed males (EEFM)
Summary
Biparental care of offspring occurs in only a minority of mammals [1] and is generally encountered in species that are socially monogamous and where the male remains bonded to the female during the period in which the offspring are conceived, suckled and weaned [2]. It occurs in primates, including humans [3], and in some rodents, but not in laboratory rats and mice, which are the most commonly used species for behavioral studies. Impaired parental care can have dramatic epigenetic and phenotypic consequences on the young [11] and likely contributes to maladjusted social behaviors [12,13,14]
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