A Brief Guide to Studying Fear in Developing Rodents: Important Considerations and Common Pitfalls

Cowan, Caitlin S. M.; Richardson, Rick

doi:10.1002/cpns.44

Cited by 11 publications

(7 citation statements)

References 73 publications

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“…A maximum of two animals from the same litter were used in any given group. Where two rats of the same sex from the same litter were included, the data were averaged and treated as a single data point for the statistical analyses (Cowan & Richardson, ). All animals were treated in accordance with The Australian Code of Practice for the Care and Use of Animals for Scientific Purposes 7th Edition (2004), and all procedures were approved by the Animal Care and Ethics Committee at the University of New South Wales.…”

Section: Methodsmentioning

confidence: 99%

Early‐life stress leads to sex‐dependent changes in pubertal timing in rats that are reversed by a probiotic formulation

Cowan

Richardson

2018

Developmental Psychobiology

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Puberty marks the beginning of a period of dramatic physical, hormonal, and social change. This instability has made adolescence infamous as a time of "storm and stress" and it is well-established that stress during adolescence can be particularly damaging. However, prior stress may also shape the adolescent experience. In the present series of experiments, we observed sex-specific effects of early-life maternal separation stress on the timing of puberty onset in the rat. Specifically, stressed females exhibited earlier pubertal onset compared to standard-reared females, whereas stressed males matured later than their standard-reared counterparts. Further, we demonstrated that a probiotic treatment restores the normative timing of puberty onset in rodents of both sexes. These results are in keeping with previous findings that probiotics reverse stress-induced changes in learned fear behaviors and stress hormone levels, highlighting the remarkable and wide-ranging restorative effects of probiotics in the context of early-life stress.

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Section: Methodsmentioning

confidence: 99%

Early‐life stress leads to sex‐dependent changes in pubertal timing in rats that are reversed by a probiotic formulation

Cowan

Richardson

2018

Developmental Psychobiology

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“…During juvenility (often noted as ∼P18‐29; Bell, 2018; Cowan & Richardson, 2018), mice and rats venture out of the nest more frequently, thereby increasing encounters with threatening stimuli (Bell, 2018; Brust et al., 2015). As a result, this is a crucial time for fear‐related systems to come online and ensure survival.…”

Section: Developmental Differences In Fear Processing In Rodentsmentioning

confidence: 99%

“…Infant and juvenile rodents are initially kept with the dam in large groups of up to 14 pups, at an average of 6‐8 in a lab setting (Jalali et al., 2016). Some studies cull litters to a certain size shortly after parturition—e.g., 8‐10 pups (Brasser & Spear, 2004; Kreiker et al., 2021), 9 pups (Carew & Rudy, 1991), or 10 pups (Revillo, Castello, et al., 2014)—in order to better control for litter effects (for a recommendation to standardize litter sizes as early as possible, see Cowan & Richardson, 2018). Following weaning, the standard procedure in animal facilities is to house same‐sex littermates together in groups of 3‐5 (with considerable variation, see below).…”

Section: Breeding and Housing Conditionsmentioning

confidence: 99%

“…The confluence of these factors imposes serious challenges and potentially confounds the study of fear processing during early life. Here we provide a brief overview of developmental differences in fear processing in rodents, followed by a discussion of some potential underlying factors, providing recommendations aimed at minimizing experimental variability, with a focus on mouse studies (also see the exemplary overview by Cowan & Richardson, 2018). NOTE: All protocols involving live animals must be reviewed and approved by an Institutional Animal Care and Use Committee (IACUC) and must conform to government regulations for the care and use of laboratory animals.…”

Section: Introductionmentioning

confidence: 99%

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Minimizing Variability in Developmental Fear Studies in Mice: Toward Improved Replicability in the Field

Premachandran,

Wilkin,

Arruda‐Carvalho

2024

Current Protocols

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In rodents, the first weeks of postnatal life feature remarkable changes in fear memory acquisition, retention, extinction, and discrimination. Early development is also marked by profound changes in brain circuits underlying fear memory processing, with heightened sensitivity to environmental influences and stress, providing a powerful model to study the intersection between brain structure, function, and the impacts of stress. Nevertheless, difficulties related to breeding and housing young rodents, preweaning manipulations, and potential increased variability within that population pose considerable challenges to developmental fear research. Here we discuss several factors that may promote variability in studies examining fear conditioning in young rodents and provide recommendations to increase replicability. We focus primarily on experimental conditions, design, and analysis of rodent fear data, with an emphasis on mouse studies. The convergence of anatomical, synaptic, physiological, and behavioral changes during early life may increase variability, but careful practice and transparency in reporting may improve rigor and consensus in the field. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC.

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“…The functional relevance of these alterations is unknown, but results in mammals and lizards suggests that defective differentiation of hippocampal neurons and the seminiferous cord causes cognitive and reproductive problems (see above). Studies in rodents suggest that males are more vulnerable to developmental disruption (Dimatelis et al, 2015;Cowan and Richardson, 2018;de Melo et al, 2018), but in ectotherms some studies associate better phenotypes with maleproducing environmental conditions (Freedberg et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Negative Effects on Neurogenesis, Ovariogenesis, and Fitness in Sea Turtle Hatchlings Associated to ex situ Incubation Management

et al. 2022

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Sea turtle egg relocation and hatchery incubation (hereafter termed ex situ incubation) is an effective strategy to protect clutches when in situ egg incubation is not viable. Nevertheless, it negatively affects the ontogenesis of male gonads and brain areas homologous to the mammalian hippocampus, as well as body size and fitness. Thus, it is imperative to analyze the effects of ex situ incubation on other developmental aspects and extend these observations to females. This work evaluated the effect of ex situ management on neurogenesis (cell proliferation in the dorsal and medial ventricular zones, neuronal integration in the dorsomedial and medial cortices), ovary cell proliferation, body size (mass and length) and self-righting ability. Additionally, this study examined if the incubation microenvironment is different between in situ and ex situ nests and whether it could contribute to explain the biological traits. An analysis of principal components showed differences in biological variables of hatchlings between in situ and ex situ clutches, driven by contrasting temperatures and silt composition. Each biological variable was also analyzed with linear mixed models using in situ vs. ex situ clutches, abiotic variables and their interaction. Turtles from ex situ clutches showed: (1) fewer proliferating cells in the dorsal and medial ventricular zones; (2) less mature neurons in the dorsomedial and medial cortices; (3) ovaries with a lesser number of proliferating cells; (4) lower body mass and length at emergence; and (5) slower self-righting time. Together, the results suggest that ex situ incubation in hatcheries is related to a slowing down of neurogenesis, ovariogenesis, body size and self-righting ability in hatchlings. Future studies should evaluate the effect of ex situ incubation on cognitive and reproductive performance to understand the long-term consequences of altered organogenesis. These studies should also disentangle the differential contribution of egg movement, reburial, nesting environment and parental origin to development. This information would likely result in better conservation strategies for sea turtles.

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A Brief Guide to Studying Fear in Developing Rodents: Important Considerations and Common Pitfalls

Cited by 11 publications

References 73 publications

Early‐life stress leads to sex‐dependent changes in pubertal timing in rats that are reversed by a probiotic formulation

Early‐life stress leads to sex‐dependent changes in pubertal timing in rats that are reversed by a probiotic formulation

Minimizing Variability in Developmental Fear Studies in Mice: Toward Improved Replicability in the Field

Negative Effects on Neurogenesis, Ovariogenesis, and Fitness in Sea Turtle Hatchlings Associated to ex situ Incubation Management

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