Abstract
Rodent pups use vocalizations to communicate with one or both parents in biparental species, such as California mice (Peromyscus californicus). Previous studies have shown California mice developmentally exposed to endocrine disrupting chemicals, bisphenol A (BPA) or ethinyl estradiol (EE), demonstrate later compromised parental behaviors. Reductions in F1 parental behaviors might also be due to decreased emissions of F2 pup vocalizations. Thus, vocalizations of F2 male and female California mice pups born to F1 parents developmentally exposed to BPA, EE, or controls were examined. Postnatal days (PND) 2–4 were considered early postnatal period, PND 7 and 14 were defined as mid-postnatal period, and PND 21 and 28 were classified as late postnatal period. EE pups showed increased latency to emit the first syllable compared to controls. BPA female pups had decreased syllable duration compared to control and EE female pups during the early postnatal period but enhanced responses compared to controls at late postnatal period; whereas, male BPA and EE pups showed greater syllable duration compared to controls during early postnatal period. In mid-postnatal period, F2 BPA and EE pups emitted greater number of phrases than F2 control pups. Results indicate aspects of vocalizations were disrupted in F2 pups born to F1 parents developmentally exposed to BPA or EE, but their responses were not always identical, suggesting BPA might not activate estrogen receptors to the same extent as EE. Changes in vocalization patterns by F2 pups may be due to multigenerational exposure to BPA or EE and/or reduced parental care received.
Highlights
Diverse rodent species primarily communicate by ultrasonic vocalizations (USVs, sounds above 20 kHz)
We have shown that male and female California mice developmentally exposed to the endocrine disrupting chemicals (EDCs), bisphenol A (BPA), which can exhibit weak estrogenic activity or ethinyl estradiol (EE, estrogen present in birth control pills and estrogen receptor positive control for the current studies) demonstrate reduced biparental care, including duration of time female spent nursing the pups, time spent in the nest for both parents, and time spent grooming the pups [15]
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 weight 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 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 [29, 30], and 3) AIN93G diet supplemented with 0.1 parts per billion of EE, as the FDA required positive control for BPA studies based on the fact that BPA is considered a weak estrogen [31]
Summary
Diverse rodent species primarily communicate by ultrasonic vocalizations (USVs, sounds above 20 kHz). Pup vocalizations may be essential in triggering parental care [2, 5, 8] This may be especially important in those that are unable to regulate their own body temperature until later in life, which includes neotropical singing mice (Scotinomys spp.) [4] and California mice [9,10,11]. The latter species are monogamous and biparental [10, 12,13,14], and while the dam is foraging, her male partner will huddle over the pups to prevent a decline in pup body temperature [9, 10]. We have previously shown that California mice pup vocalizations begin to decline around the time, postnatal day (PND) 15, they can regulate their own body temperature
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