Biology subjects

Burghardt, N. S.

Publications and source records attributed to Burghardt, N. S..

7 recordsLinked to original sources

bioRxiv2026

Vulnerability and Resilience to Activity-Based Anorexia is Not Sex-Dependent

IntroductionAnorexia nervosa (AN) is more prevalent in women than men, although rates in men are rising. Animal models can provide insight into whether this differential prevalence is rooted in biological mechanisms, but prior studies have yielded conflicting findings. Using the activity-based anorexia (ABA) model, we previously demonstrated that female mice exhibit distinct vulnerable and resilient phenotypes. Here, we use this phenotypic framework to investigate sex differences in ABA susceptibility. MethodsWe tested young adult male C57BL/6N mice using the same ABA protocol used to test age-matched C57BL/6N females. Individual differences in daily bodyweight, food intake, water intake, and wheel running were analyzed and compared across sexes. ResultsMales exhibit the same vulnerable and resilient phenotypes as females, with no sex difference in the proportion of mice exhibiting each phenotype or the repertoire of behaviors characterizing them. In both sexes, vulnerable mice exhibit catastrophic weight loss driven by excessive light cycle running, while resilient mice exhibit weight stabilization driven by adaptive changes in consumption. Running during the feeding window revealed that vulnerability is not driven by a decision to run instead of eat in either sex. ConclusionsABA models adaptive and maladaptive responses to food restriction in both sexes. Behavioral responses to starvation are similar across sexes, suggesting that sex differences in AN prevalence may be driven by stronger sociocultural pressures faced by women to lose weight.

neuroscience↗

bioRxiv2025

Methamphetamine Conditioned Place Preference in Adolescent Mice: Interaction Between Sex and Strain

BackgroundMethamphetamine (METH) use is higher in adolescent women than men. While rodent studies support a sex difference in the reinforcing effects of METH, few have investigated sex differences in the underlying neural circuits, none of which tested rodents during adolescence. AimsInvestigate whether there are sex differences in the rewarding effects of METH in two strains of adolescent mice that are commonly used to generate transgenic lines. Identify changes in associated neural circuits. MethodsWe tested METH-induced conditioned place preference (CPP) in male and female 129Sv/Ev and C57Bl/6 mice during middle adolescence using 1mg/kg of METH. Behaviorally-induced upregulation of c-Fos protein expression was quantified in the nucleus accumbens (NAc) and area CA1 of the hippocampus following the post-conditioning test. ResultsIn C57Bl/6 mice, METH induced CPP in females, but not males. Conversely, METH-induced CPP in 129Sv/Ev males, but not females. In both strains, groups that exhibited CPP had more c-Fos+ cells in the NAc and CA1 when compared to saline-treated control groups. The number of c-Fos+ cells in these two brain regions correlated in groups exhibiting CPP, indicating increased NAc-CA1 communication during retrieval of the conditioned memory. Finally, we found evidence of behavioral sensitization in 129Sv/Ev males only. ConclusionsOur study reveals that the rewarding effects of the METH in adolescent mice are both sex- and strain-dependent, indicating that METH response may result from an interaction between sex-specific and genetic mechanisms. Our findings will be informative when selecting an appropriate background strain in future studies using genetically modified mice.

neuroscience↗

bioRxiv2024

Social Isolation During Adolescence Differentially Affects Spatial Learning in Adult Male and Female Mice

Social isolation is a risk factor for cognitive impairment. Adolescents may be particularly vulnerable to these effects, because they are in a critical period of development marked by significant physical, hormonal, and social changes. However, it is unclear if the effects of social isolation on learning and memory are similar in both sexes or if they persist into adulthood after a period of recovery. We socially isolated male and female 129Sv/Ev mice throughout adolescence (post-natal days 29-56), provided a 2-week re-socialization recovery period, and then tested spatial learning and cognitive flexibility in the active place avoidance task. After behavioral testing, mice were injected with 5-bromo-2-deoxyuridine (BrdU) so that lasting effects of social isolation on cell proliferation in the dentate gyrus could be examined. We found that in males, isolation led to a modest impairment in the rate of initial spatial learning, whereas in females, initial learning was unaffected. However, when the location of the shock zone was switched during the conflict variant of the task, cognitive flexibility was impaired in females only. Similarly, social isolation reduced cell proliferation in the ventral dentate gyrus only in females. Together, these findings indicate that social isolation during adolescence differentially impairs spatial processing in males and females, with effects that persist into adulthood.

neuroscience↗

bioRxiv2024

Chronic Social Defeat Stress Gives Rise to Social Avoidance Through Fear Learning

Chronic social defeat stress (CSDS), a widely used rodent model of stress, reliably leads to decreased social interaction in stress susceptible animals. Here, we investigate a role for fear learning in this response using 129Sv/Ev mice, a strain that is more vulnerable to CSDS than the commonly used C57BL/6 strain. We first demonstrate that defeated 129Sv/Ev mice avoid a CD-1 mouse, but not a conspecific, indicating that motivation to socialize is intact in this strain. CD-1 avoidance is characterized by approach behavior that results in running in the opposite direction, activity that is consistent with a threat response. We next test whether CD-1 avoidance is subject to the same behavioral changes found in traditional models of Pavlovian fear conditioning. We find that associative learning occurs across 10 days CSDS, with defeated mice learning to associate the color of the CD-1 coat with threat. This leads to the gradual acquisition of avoidance behavior, a conditioned response that can be extinguished with 7 days of repeated social interaction testing (5 tests/day). Pairing a CD-1 with a tone leads to second-order conditioning, resulting in avoidance of an enclosure without a social target. Finally, we show that social interaction with a conspecific is a highly variable response in defeated mice that may reflect individual differences in generalization of fear to other social targets. Our data indicate that fear conditioning to a social target is a key component of CSDS, implicating the involvement of fear circuits in social avoidance.

animal behavior and cognition↗

bioRxiv2023

Serotonergic modulation of the BNST-CeA circuit promotes sex differences in fear learning

Post-traumatic stress disorder (PTSD) is characterized by intense fear memory formation and is diagnosed more often in women than men. Here, we show that serotonin differentially affects fear learning and communication in the extended amygdala of male and female mice. Females showed higher sensitivity to the effects of pharmacologically increasing serotonin during auditory fear conditioning, which enhanced fear memory recall in both sexes. Optogenetic stimulation of dorsal raphe terminals in the anterior dorsal bed nucleus of the stria terminalis (adBNST) during fear conditioning increased c-Fos expression in the BNST and central nucleus of the amygdala (CeA), and enhanced fear memory recall via activation of adBNST 5-HT2C receptors in females only. Likewise, in females only, serotonin stimulation during learning enhanced adBNST-CeA high gamma (90-140Hz) synchrony and adBNST-to-CeA communication in high gamma during fear memory recall. We conclude that sex differences in the raphe-BNST-CeA circuit may increase risk of PTSD in women.

neuroscience↗

bioRxiv2022

Granulocyte Colony Stimulating Factor causes cerebellar deficits and anxiety in a mouse model of CSF-1 receptor-related leukoencephalopathy

Colony stimulating factor (CSF) receptor-1 (CSF-1R)-related leukoencephalopathy (CRL) is an adult-onset, demyelinating neurodegenerative disease caused by autosomal dominant mutations in CSF1R, modeled by the Csf1r+/- mouse. The expression of Csf2, encoding granulocyte- macrophage CSF (GM-CSF) and of Csf3, encoding granulocyte CSF (G-CSF), are elevated in both mouse and human CRL brains. While monoallelic targeting of Csf2 has been shown to attenuate many behavioral and histological deficits of mouse CRL, including cognitive dysfunction and demyelination, the contribution of Csf3 has not been explored. In this manuscript, we investigate the behavioral, electrophysiological and histopathological phenotypes of CRL mice following monoallelic targeting of Csf3. We show that Csf3 heterozygosity normalized the Csf3 levels in Csf1r+/- mouse brains and ameliorated anxiety-like behavior, motor coordination and social interaction deficits, but not their cognitive impairment. Consistent with this, Csf3 heterozygosity attenuated microglial activation in the cerebellum and in the ventral but not in the dorsal hippocampus. Csf3 heterozygosity also failed to prevent demyelination. Csf1r+/- mice exhibited altered synaptic activity in the deep cerebellar nuclei (DCN) associated with increased deposition of the complement factor C1q on glutamatergic synapses and with increased engulfment of glutamatergic synapses by DCN microglia. These phenotypes were significantly ameliorated by monoallelic deletion of Csf3. Our findings indicate that G-CSF and GM-CSF play non-overlapping roles in mouse CRL development and suggest that G-CSF could be an additional therapeutic target in CRL.

neuroscience↗

bioRxiv2020

PKMζ traces hippocampal LTP maintenance and spatial long-term memory

PKM{zeta} is an autonomously active PKC isoform crucial for the maintenance of synaptic long-term potentiation (LTP) and long-term memory. Unlike other protein kinases that are transiently stimulated by second messengers, PKM{zeta} is persistently activated through sustained increases in kinase protein expression. Therefore, visualizing increases in PKM{zeta} expression during long-term memory storage might reveal the sites of its persistent action and thus the location of memory-associated LTP maintenance in the brain. Using quantitative immunohistochemistry validated by the lack of staining in PKM{zeta}-null mice, we examined the amount and distribution of PKM{zeta} in subregions of the hippocampal formation of wild-type mice during LTP maintenance and spatial long-term memory storage. During LTP maintenance in hippocampal slices, PKM{zeta} increases in the pyramidal cell body and stimulated dendritic layers of CA1 for at least 2 h. During spatial memory storage, PKM{zeta} increases in CA1 pyramidal cells for at least 1 month, paralleling the persistence of the memory. The subset of CA1 pyramidal cells that are tagged by immediate early gene Arc-driven transcription of fluorescent proteins, whose expression increases during initial memory formation, also expresses the persistent increase of PKM{zeta} during memory storage. In the memory-tagged cells, the increased PKM{zeta} expression persists in dendritic compartments within stratum radiatum for 1 month, indicating the long-term storage of information in the CA3-to-CA1 pathway during remote spatial memory. We conclude that persistent increases in PKM{zeta} trace the molecular mechanism of LTP maintenance and thus the sites of information storage within brain circuitry during long-term memory.

neuroscience↗