Sex differences in gut microbiota modulation of aversive conditioning, open field activity, and basolateral amygdala dendritic spine density

Abstract

Gut microbiota influence numerous aspects of host biology, including brain structure and function. Growing evidence implicates gut microbiota in aversive conditioning and anxiety‐related behaviors, but research has focused almost exclusively on males. To investigate whether effects of gut dysbiosis on aversive learning and memory differ by sex, adult female and male C57BL/6N mice were orally administered a moderate dose of nonabsorbable antimicrobial medications (ATMs: neomycin, bacitracin, and pimaricin) or a control over 10 days. Changes in gut microbiome composition were analyzed by 16S rRNA sequencing. Open field behavior, cued aversive learning, context recall, and cued recall were assessed. Following behavioral testing, the morphology of basolateral amygdala (BLA) principal neuron dendrites and spines was characterized. Results revealed that ATMs induced gut dysbiosis in both sexes, with stronger effects in females. ATMs also exerted sex‐specific effects on behavior and neuroanatomy. Males were more susceptible than females to microbial modulation of locomotor activity and anxiety‐like behavior. Females were more susceptible than males to ATM‐induced impairments in aversive learning and cued recall. Context recall remained intact, as did dendritic structure of BLA principal neurons. However, ATMs exerted a sex‐specific effect on spine density. A second experiment was conducted to isolate the effects of gut perturbation to cued recall. Extinction was also examined. Results revealed no effect of ATMs on cued recall or extinction, suggesting that gut dysbiosis preferentially impacts aversive learning. These data shed new light on how gut microbiota interact with sex to influence aversive conditioning, open field behavior, and BLA dendritic spine architecture.

Sex-specific divergent maturational trajectories in the postnatal rat basolateral amygdala

“…A growing body of evidence indicates sex-differences in these functions ( Cahill et al., 2004 ; Canli et al., 2002 ; Greiner et al., 2019 ; Gruene et al., 2015 ; Lebron-Milad and Milad, 2012 ). Moreover, the BLA is implicated in the etiology of neuropsychiatric diseases including post-traumatic stress disorder, depression, and anxiety ( Daviu et al., 2019 ; Mahan and Ressler, 2012 ; Nestler et al., 2002 ), characterized by their higher prevalence in the female population ( Christiansen and Berke, 2020 ; Kuehner, 2017 ; McLean et al., 2011 ).While the study of females’ brains and sex differences in preclinical research have recently gained momentum ( Shansky and Murphy, 2021 ), sex differences in the functions of the BLA have mostly been studied in pathological rodent models ( Blume et al., 2019 ; Geary et al., 2021 ; Guadagno et al., 2020 ; Przybysz et al., 2021 ) and the physiological development of the female BLA remains partially understood.…”