2026 ECNP Congress

PS01-1143

Neonatal limited bedding and nesting experience drives sex-specific panic-like defensive behaviours and microglial phenotypic alterations in mice

Helio Zangrossi Jr. — J. Nascimento-Silva, A. Rocha-Gomes, V. Mosienko · University of Sao Paulo, Department of Pharmacology- School of Medicine of Ribeirao Preto, Ribeirão Preto, Brazil

2026 ECNP Congress

Introduction

Panic Disorder (PD) is a chronic and disabling psychiatric condition characterised by recurrent and unexpected panic attacks. Human epidemiological evidence indicates that exposure to childhood adversity represents a significant risk factor for mental health disorders, including anxiety and PD. The limited bedding and nesting (LBN) protocol, which models neonatal adversity through environmental resource scarcity, is a widely used animal paradigm associated with increased vulnerability to aversive stimuli in adulthood [1]. LBN experience may also drive long-lasting alterations in microglial phenotype, a phenomenon associated with behavioural changes observed in adulthood [2]. However, it remains unclear whether these microglial alterations contribute to PD susceptibility and how they manifest across brain regions implicated in its pathophysiology, such as the periaqueductal grey (PAG) and the dorsal raphe nucleus (DRN) [3].

Objectives

We here investigated the consequences of prior LBN experience for the expression of anxiety- and panic-like behaviours in male and female offspring in adulthood. We also investigated whether microglial morphological alterations within the PAG and DRN were associated with the behavioural outcomes evaluated.

Methods

C57BL/6J lactating dams and their offspring were submitted to the LBN protocol between postnatal days (PND) 2-9. In adulthood (PND90-94), we assessed anxiety-like behaviour in male and female offspring using the elevated plus maze, open field, and light-dark box tests, followed by exposure to 20% CO₂, a well-known panicogenic stimulus that elicits panic attacks in humans and panic-like escape responses in rodents. Iba-1 immunofluorescence and confocal microscopy were used to analyse microglial morphology within the PAG subregions, i.e., dorsomedial, dorsolateral, lateral and ventral PAG (dmPAG, dlPAG, lPAG, and vlPAG, respectively); as well as the DRN subareas: dorsal nucleus and lateral wings (DRD and lwDRD, respectively).

Results

Male offspring exposed to LBN exhibited reduced time spent in the light compartment (p<0.05), suggesting an anxiogenic effect, along with increased locomotor activity, an effect also observed in females. During CO₂ exposure, LBN males showed a significant increase (p<0.05) in the number of jumps, indicative of a panicogenic effect. Morphological analysis of microglia in LBN-exposed males revealed region-specific alterations, including increased soma size in the dmPAG, vlPAG, and lwDRN, and reduced process length in the dlPAG and lPAG, consistent with a shift towards an amoeboid and more immunoresponsive phenotype. In LBN-exposed females, increased process length was observed in the dmPAG, dlPAG, and DRD compared to controls, suggestive of a rod-shaped microglial morphology potentially associated with a more regulatory or adaptive phenotype.

Conclusions:These results show that neonatal LBN experience has sex-specific consequences for the expression of anxiety- and panic-like behaviours, with males showing greater susceptibility. The immunoresponsive amoeboid microglial phenotype observed in LBN males, in contrast to a more transitional morphology in females, may be related to distinct behavioural profiles between the sexes. Together, these findings suggest that LBN experience induces long-lasting, sex-dependent alterations in microglial phenotype, indicating a potential role for these cells in PD pathophysiology.

References

  1. Vilela-Costa, H.H., Hernandes, P.M., Nascimento-Silva, J.M., Frias, A.T., Almada, R. C., Lovick, T.A., Zangrossi Jr, H., 2024. Neonatal limited bedding and nesting experience may lead to a sex-dependent increase in panic-like defensive behaviours in adult mice. Eur. J. Neurosci. 60, 5900–5911.
  2. Hoeijmakers, L., Ruigrok, S.R., Amelianckhi, A., Ivan, D., van Dam, A., Lucassen, P.J., Korosi, A., 2017. Early-life stress lastingly alters the neuroinflammatory response to amyloid pathology in an Alzheimer’s disease mouse model. Brain Behav. Immun. 63, 160–175 (2017).
  3. Graeff, F. G., 2017. Translational approach to the pathophysiology of panic disorder: Focus on serotonin and endogenous opioids. Neurosci. Biobehav. Rev. 76, 48–55.