Biology subjects

Packard, B. A.

Publications and source records attributed to Packard, B. A..

5 recordsLinked to original sources

bioRxiv2026

Adolescent Stress Exposure: Behavioral Consequences and Molecular Mechanisms in Corticolimbic Networks

IntroductionAdolescence is a sensitive developmental period during which chronic stress can induce lasting adaptations in corticolimbic circuits involved in stress regulation, cognition, and emotional behavior. We examined the long-term behavioral, endocrine, and molecular consequences of adolescent chronic variable stress (CVS) in male and female rats, focusing on the infralimbic cortex (IL) and basolateral amygdala (BLA) MethodsSprague Dawley rats of both sexes were exposed to CVS during late adolescence and evaluated in adulthood after an extensive recovery period. Behavioral testing included cued fear conditioning and extinction recall, delayed spatial win-shift, novel object recognition, Morris water maze, three-chamber social behavior, and passive avoidance. HPA-axis reactivity to acute restraint was assessed. Targeted qPCR was used to measure stress-related gene expression in the IL and BLA immediately after stress or after a 5-week recovery period ResultsAdolescent CVS did not cause generalized cognitive impairment, but instead produced selective, sex-specific effects. Females had reduced HPA responses to acute stress and mild deficits in delayed spatial win-shift performance, together with long-term IL changes in genes related to adrenergic signaling, plasticity, and GABA clearance. Males showed enhanced Morris water maze probe retention, weaker novel object discrimination, altered passive avoidance with marked inter-individual variability, and enhanced social preference. At the molecular level, males exhibited long-term upregulation of Fkbp5 in IL and downregulation of PACAP, 1D adrenergic receptor, and proenkephalin in BLA, whereas females showed delayed PACAP upregulation in BLA DiscussionAdolescent CVS induces persistent, sex- and region-specific recalibration of corticolimbic function, supporting distinct patterns of vulnerability and resilience, rather than uniform stress pathology.

animal behavior and cognition↗

bioRxiv2024

Sex-Specific Regulation of Behavioral Responses to Single Prolonged Stress: Role of PACAP

Post-Traumatic Stress Disorder (PTSD) is a debilitating condition in which a traumatic experience triggers symptoms related to re-experiencing, avoidance, arousal, and mood dysregulation. PTSD negatively impacts 6% of people during their lifetime, with women being disproportionally affected and exhibiting different, more severe symptoms than men. Despite this widespread impact, the molecular mechanisms underlying PTSD and its sex differences remain poorly understood. Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is a neuropeptide which participates in fine-tuning circuitry throughout the brain and has been associated with PTSD in humans, especially in women. Here, we use Single Prolonged Stress (SPS), an animal model of PTSD, to explore the roles of PACAP and sex in PTSD-like behaviors. Specifically, a PACAP agonist or antagonist was infused into the infralimbic (IL) prefrontal cortex, a region key to regulating fear- and anxiety-related behaviors, prior to SPS in male and female rats. One week later, rats were tested in open field/novel object, elevated plus maze, and social interaction. Utilizing a behavioral indexing method, we were able to uncover SPS effects in PTSD-related behavioral domains that were differentially impacted by PACAP manipulations in males and females. While both sexes exhibited increased threat avoidance and decreased threat assessment following SPS, females increased sociability while males decreased sociability. Males also appeared to be protected by IL PACAP antagonism while female SPS phenotypes were exacerbated by IL PACAP agonism. Furthermore, RNAscope revealed that PACAP in the prefrontal cortex responds differently to SPS in males and females. Together, these findings suggest complex relationships between SPS, sex, and IL PACAP which may have important implications for treating PTSD in men and women. HIGHLIGHTSO_LISPS induces different PTSD-like phenotypes in male and female rats C_LIO_LISPS increases threat avoidance and decreases threat appraisal in both sexes C_LIO_LISociability is decreased in males but increased in females following SPS C_LIO_LIIL PACAP manipulation exerts diverging SPS behavioral effects in males and females C_LIO_LIPrefrontal PACAP signaling plays a sex-specific role in SPS molecular mechanisms C_LI

neuroscience↗

bioRxiv2019

Prefrontal Cortex Regulates Chronic Stress-Induced Cardiovascular Susceptibility

The medial prefrontal cortex (mPFC) is necessary for appropriate appraisal of stressful information, as well as coordinating visceral and behavioral processes. However, prolonged stress impairs mPFC function and prefrontal-dependent behaviors. Additionally, chronic stress induces sympathetic predominance, contributing to health detriments associated with autonomic imbalance. Previous studies identified a subregion of rodent prefrontal cortex, infralimbic cortex (IL), as a key regulator of neuroendocrine-autonomic integration after chronic stress, suggesting that IL output may prevent chronic stress-induced autonomic imbalance. In the current study, we tested the hypothesis that the IL regulates hemodynamic, vascular, and cardiac responses to chronic stress. To address this hypothesis, a viral-packaged siRNA construct was used to knockdown vesicular glutamate transporter 1 (vGluT1) and reduce glutamate packaging and release from IL projection neurons. Male rats were injected with a vGluT1 siRNA-expressing construct or GFP control into the IL and then remained as unstressed controls or were exposed to chronic variable stress (CVS). IL vGluT1 knockdown increased heart rate and mean arterial pressure (MAP) reactivity, while CVS increased chronic MAP only in siRNA-treated rats. In a separate cohort, CVS and vGluT1 knockdown interacted to impair both endothelial-dependent and endothelial-independent vasoreactivity ex vivo. Furthermore, vGluT1 knockdown and CVS increased histological markers of fibrosis and hypertrophy. Thus, knockdown of glutamate release from IL projection neurons indicates that these cells are necessary to prevent the enhanced physiological responses to stress that promote susceptibility to cardiovascular pathophysiology. Ultimately, these findings provide evidence for a neurobiological mechanism mediating the relationship between stress and poor cardiovascular health outcomes.\n\nClinical perspectiveWhat is new? O_LIKnockdown of glutamate release from infralimbic cortex increases heart rate and arterial pressure reactivity\nC_LIO_LIDecreased infralimbic glutamate output leads to vascular dysfunction after chronic stress\nC_LIO_LIThese functional changes associate with histological indicators of cardiac hypertrophy, as well as vascular hypertrophy and fibrosis\nC_LI\n\nWhat are the clinical implications? O_LIThese studies provide a neurobiological mechanism that may account for the link between long-term stress and increased cardiovascular disease risk\nC_LI

neuroscience↗

bioRxiv2019

Selective modulation of the glucocorticoid receptor with CORT108297 during chronic adolescent stress evokes sex specific effects in adulthood.

Adolescent animals are vulnerable to the effects of stress on brain development. We hypothesized that long-term effects of adolescent chronic stress are mediated by glucocorticoid receptor (GR) signaling. We used a specific GR modulator (CORT108297) to pharmacologically disrupt GR signaling in adolescent rats during exposure chronic variable stress (CVS). Male and female rats received 30mg/kg of drug concomitantly with a 2-week CVS protocol starting at PND46. Emotional reactivity (open field) and coping behaviors (forced swim test (FST)) were then tested in adulthood, 5 weeks after the end of the CVS protocol. Blood samples were collected two days before FST and serial samples after the onset of the swim test to determine baseline and stress response levels of HPA hormones respectively.\n\nOur results support differential behavioral, physiological and stress circuit reactivity to adolescent chronic stress exposure in males vs. females, with variable involvement of GR signaling. In response to adolescent stress, males had heightened reactivity to novelty and exhibited marked reduction in neuronal excitation following swim stress in adulthood, whereas females developed a passive coping strategy and enhanced HPA axis stress reactivity. Only the latter effect was attenuated by treatment with the GR modulator C108297. Our data suggest that adolescent stress differentially affects emotional behavior and circuit development in females, and that GR plays a role in driving some but not all sequelae of adolescent stress.

neuroscience↗

bioRxiv2019

Use of CRISPR/Cas9 Gene Targeting to Conditionally Delete Glucocorticoid Receptors in Rat Brain

Glucocorticoid receptors (GR) have diverse functions relevant to maintenance of homeostasis and adaptation to environmental challenges. Understanding the importance of tissue-specific GR function in physiology and behavior has been hampered by near-ubiquitous localization in brain and body. Here we use CRISPR/Cas9 gene editing to create a conditional GR knockout in Sprague Dawley rats. To test the impact of cell-and region-specific GR deletion on physiology and behavior, we targeted GR knockout to output neurons of the prelimbic cortex. Prelimbic deletion of GR in females caused deficits in acquisition and extinction of fear memory during auditory fear conditioning, whereas males exhibit enhanced active-coping behavior during forced swim. Our data support the utility of this conditional knockout rat to afford high-precision deletion of GR across a variety of contexts, ranging from neuronal depletion to circuit-wide manipulations, leveraging the behavioral tractability and enhanced brain size of the rat as a model organism.

neuroscience↗