Inescapable Shock Research Articles

Prenatal immune activation in rats and adult exposure to inescapable shocks reveal sex-dependent effects on fear conditioning that might be relevant for schizophrenia

Prenatal infection is considered a relevant factor for neurodevelopmental alterations and psychiatric diseases. Administration of bacterial and viral components during pregnancy in rodents results in maternal immune activation (MIA), leading to schizophrenia-like neurochemical and behavioral changes. Despite some evidence for abnormal fear conditioning in schizophrenia, only a few animal studies have focused on this issue. Therefore, we addressed the impact of the administration of the viral mimetic polyI:C to pregnant Long-Evans rats on the adult offspring response to inescapable shocks (IS) and contextual fear conditioning. In males, polyI:C induced a greater endocrine (plasma ACTH) response to IS and both polyI:C and IS enhanced fear conditioning and generalization to a completely different novel environment (hole-board), with no additive effects, probably due to a ceiling effect. In contrast, a modest impact of polyI:C and a lower impact of IS on contextual fear conditioning and generalization was observed in females. Thus, the present results demonstrate that polyI:C dramatically affected fear response to IS in adult males and support the hypothesis that males are more sensitive than females to this treatment. This model might allow to explore neurobiological mechanisms underlying abnormal responsiveness to fear conditioning and stressors in schizophrenia.

A SMARTR workflow for multi-ensemble atlas mapping and brain-wide network analysis.

In the last decade, activity-dependent strategies for labelling multiple immediate early gene (IEG) ensembles in mice have generated unprecedented insight into the mechanisms of memory encoding, storage, and retrieval. However, few strategies exist for brain-wide mapping of multiple ensembles, including their overlapping population, and none incorporate capabilities for downstream network analysis. Here, we introduce a scalable workflow to analyze traditionally coronally-sectioned datasets produced by activity-dependent tagging systems. Intrinsic to this pipeline is simple multi-ensemble atlas registration and statistical testing in R (SMARTR), an R package which wraps mapping capabilities with functions for statistical analysis and network visualization. We demonstrate the versatility of SMARTR by mapping the ensembles underlying the acquisition and expression of learned helplessness (LH), a robust stress model. Applying network analysis, we find that exposure to inescapable shock (IS), compared to context training (CT), results in decreased centrality of regions engaged in spatial and contextual processing and higher influence of regions involved in somatosensory and affective processing. During LH expression, the substantia nigra emerges as a highly influential region which shows a functional reversal following IS, indicating a possible regulatory function of motor activity during helplessness. We also report that IS results in a robust decrease in reactivation activity across a number of cortical, hippocampal, and amygdalar regions, indicating suppression of ensemble reactivation may be a neurobiological signature of LH. These results highlight the emergent insights uniquely garnered by applying our analysis approach to multiple ensemble datasets and demonstrate the strength of our workflow as a hypothesis-generating toolkit.

Programmed cell death factor 4-mediated hippocampal synaptic plasticity is involved in early life stress and susceptibility to depression

Early life stress (ELS) increases the risk of depression later in life. Programmed cell death factor 4 (PDCD4), an apoptosis-related molecule, extensively participates in tumorigenesis and inflammatory diseases. However, its involvement in a person’s susceptibility to ELS-related depression is unknown. To examine the effects and underlying mechanisms of PDCD4 on ELS vulnerability, we used a “two-hit” stress mouse model: an intraperitoneal injection of lipopolysaccharide (LPS) into neonatal mice was performed on postnatal days 7–9 (P7-P9) and inescapable foot shock (IFS) administration in adolescent was used as a later-life challenge. Our study shows that compared with mice that were only exposed to the LPS or IFS, the “two-hit” stress mice developed more severe depression/anxiety-like behaviors and social disability. We detected the levels of PDCD4 in the hippocampus of adolescent mice and found that they were significantly increased in “two-hit” stress mice. The results of immunohistochemical staining and Sholl analysis showed that the number of microglia in the hippocampus of “two-hit” stress mice significantly increased, with morphological changes, shortened branches, and decreased numbers. However, knocking down PDCD4 can prevent the number and morphological changes of microglia induced by ELS. In addition, we confirmed through the Golgi staining and immunohistochemical staining results that knocking down PDCD4 can ameliorate ELS-induced synaptic plasticity damage. Mechanically, the knockdown of PDCD4 exerts neuroprotective effects, possibly via the mediation of BDNF/AKT/CREB signaling. Combined, these results suggest that PDCD4 may play an important role in the ELS-induced susceptibility to depression and, thus, may become a therapeutic target for depressive disorders.

GABAergic interneurons in the hippocampal CA1 mediate contextual fear generalization in PTSD rats.

Fear overgeneralization is widely accepted as a pathogenic marker of post-traumatic stress disorder (PTSD). Recently, GABAergic interneurons have been regarded as key players in the regulation of fear memory. The role of hippocampal GABAergic interneurons in contextual fear generalization of PTSD remains incompletely understood. In the present study, we established a rat model of PTSD with inescapable foot shocks (IFS) and observed the loss of GABAergic interneuron phenotype in the hippocampal cornu ammonis-1 (CA1) subfield. To determine whether the loss of GABAergic interneuron phenotype was associated with fear generalization in PTSD rats, we used adeno-associated virus (AAV) to reduce the expression of GAD67 in CA1 and observed its effect on fear generalization. The results showed that the reduction of GAD67 in CA1 enhanced contextual fear generalization in rats. We investigated whether the PERK pathway was involved in the GABAergic interneuron injury. Increased expression of p-PERK, CHOP, and Caspase12 in GABAergic interneurons of PTSD rats was observed. Then, we used salubrinal, an endoplasmic reticulum stress inhibitor, to modulate the PERK pathway. The salubrinal treatment significantly protected the GABAergic interneurons and relieved fear generalization in PTSD rats. In addition, the results showed that salubrinal down-regulated the expression of CHOP and Caspase12 in GABAergic interneurons of PTSD rats. In conclusion, this study provided evidence that the loss of GABAergic interneuron phenotype in CA1 may contribute to contextual fear generalization in PTSD. The PERK pathway is involved in the GABAergic interneuron injury of PTSD rats and modulating it can protect GABAergic interneurons and constrain contextual fear generalization.

Inescapable foot shock induces a PTSD-like phenotype and negatively impacts adult murine bone.

Post-traumatic stress disorder (PTSD) is associated with osteopenia, osteoporosis and increased fracture risk in the clinical population. Yet, the development of preclinical models to study PTSD-induced bone loss remains limited. In this study, we present a previously unreported model of PTSD in adult female C57BL/6 mice, by employing inescapable foot shock and social isolation, that demonstrates high face and construct validity. A subset of mice exposed to this paradigm (i.e. PTSD mice) display long-term alterations in behavioral and inflammatory indices. Using three-dimensional morphometric calculations, cyclic reference point indentation (cRPI) testing and histological analyses, we find that PTSD mice exhibit loss of trabecular bone, altered bone material quality, and aberrant changes in bone tissue architecture and cellular activity. This adult murine model of PTSD exhibits clinically relevant changes in bone physiology and provides a valuable tool for investigating the cellular and molecular mechanisms underlying PTSD-induced bone loss.

Hippocampal parvalbumin and perineuronal nets: Possible involvement in anxiety-like behavior in rats.

The excitatory-inhibitory imbalance has been considered an important mechanism underlying stress-related psychiatric disorders. In the present study, rats were exposed to 6 days of inescapable foot shock (IFS) to induce stress. The open field test and elevated plus maze test showed that IFS-exposed rats exhibited increased anxiety-like behavior. Immunofluorescence showed that IFS rats had a decreased density of GAD67-immunoreactive interneurons in the dorsal hippocampal CA1 region, while no significant change in the density of CaMKIIα-immunoreactive glutamatergic neurons was seen. We investigated the expression of different interneuron subtype markers, including parvalbumin (PV), somatostatin (SST), and calretinin (CR), and noted a marked decline in the density of PV-immunoreactive interneurons in the dorsal CA1 region of IFS rats. The perineuronal net (PNN) is a specialized extracellular matrix structure primarily around PV interneurons. We used Wisteria floribunda agglutinin lectin to label the PNNs and observed that IFS rats had an increased proportion of PNN-coated PV-positive interneurons in CA1. The number of PSD95-positive excitatory synaptic puncta on the soma of PNN-free PV-positive interneurons was significantly higher than that of PNN-coated PV-positive interneurons. Our findings suggest that the effect of IFS on the hippocampal GABAergic interneurons could be cell-type-specific. Loss of PV phenotype in the dorsal hippocampal CA1 region may contribute to anxiety in rats. The dysregulated PV-PNN relationship in CA1 after traumatic stress exposure might represent one of the neurobiological correlates of the observed anxiety-like behavior.

Inhibition of nitric oxide synthase modulates learned helplessness response in female rats

Learned helplessness is the condition of humans or animals that have learned to behave helplessly, failing to respond even though there are opportunities to help themselves by avoiding unpleasant circumstances. It was investigated the participation of nitric oxide (NO) in female Wistar rats in learned helplessness tests. The animals received acute treatment with N–nitro-l-arginine methyl ester (L-NAME, 10 mg/kg or 100 mg/kg), an inhibitor of NO synthase, 30 minutes before random inescapable shock sessions lasting 25 minutes. On the test day, the animals that received L-NAME of 10 mg/kg or 100 mg/kg 24 hours beforehand, demonstrated reduced difference between stress and non-stress groups compared with control groups. The activity of the neuronal nitric oxide synthase was lower in animals pretreated with L-NAME, especially at a dose of 100 mg/kg. These results indicate that acute inhibition of NO synthase improved learned helplessness response, suggesting that NO is involved with stress and depression.

Reduction of claudin-5 and aquaporin-4 in the rat hippocampal CA-1 and CA-3 regions of a learned helplessness model of depression

BackgroundAlthough findings from both animal and clinical research indicate that the blood-brain barrier (BBB) contributes to the pathogenesis of various psychiatric disorders (including depression), the underlying mechanisms are unknown. We investigated the levels of the tight-junction proteins claudin-5 and aquaporin-4 (AQP-4) in astrocytes of learned helplessness (LH) rats (an animal model of depression) and non-LH rats (a model of resilience). MethodsWe administered inescapable mild electric shock to rats and then identified the LH and non-LH rats by a post-shock test. The expressions of claudin-5 and AQP-4 in several brain regions of the LH and non-LH rats were then evaluated by a western blot analysis. ResultsThe levels of both claudin-5 and AQP-4 in the CA-1 and CA-3 hippocampal areas of the LH group were significantly lower than those of the control group, whereas those of the non-LH rats were not significantly different from those of the control and LH rats. ConclusionsThese results suggest that LH rats but not non-LH rats experienced down-regulations of claudin-5 and AQP-4 in the CA-1 and CA-3. It is possible that a region-specific modulation of claudin-5 and AQP-4 is involved in the mechanisms of vulnerability but not resilience in depression.

Preventing Post-Traumatic Stress Disorder (PTSD) in rats with pulsed 810 nm laser transcranial phototherapy

Post-traumatic stress disorder (PTSD) is a debilitating condition that occurs following exposure to traumatic events. Current treatments, such as psychological debriefing and pharmacotherapy, often have limited efficacy and may result in unwanted side effects, making early intervention is a more desirable strategy. In this study, we investigated the efficacy of a single dose of pulsed (10 Hz) 810 nm laser-phototherapy (P-PT) as an early intervention for preventing PTSD-like comorbidities in rats induced by single inescapable electric foot shock following the single prolonged stress (SPS&S). As indicated by the results of the open filed test, elevated plus maze test, and contextual fear conditioning test, P-PT prevented the development of anxiety and freezing behaviors in rats exposed to the SPS&S. We also compared the effects of P-PT and continuous wave 810 nm laser-phototherapy (CW-PT) in preventing PTSD-like comorbidities in rats. The results revealed that P-PT was effective in preventing both freezing and anxiety behavior in stressed rats. In contrast, CW-PT only had a preventive effect on freezing behavior but not anxiety. Additionally, P-PT significantly reduced the c-fos expression in cingulate cortex area 1(Cg1) and infralimbic cortex (IL) of stressed rats, while CW-PT had no significant effects on c-fos expression. Taken together, our results demonstrate that P-PT is a highly effective strategy for preventing the occurrence of PTSD-like comorbidities in rats.

Controllable Stress Increases Rapid Eye Movement Sleep in Rats: Regulation by the Central Nucleus of the Amygdala.

Training with inescapable shock (IS; uncontrollable stressor) is followed by significant decreases in rapid eye movement sleep (REM). However, controllability is important in the effects of stress. We examined the effects of escapable shock (ES; controllable stressor) on sleep and whether the central nucleus of the amygdala (CNA) plays a role in regulating these effects. Six Wistar rats implanted with a cannula located in CNA underwent two days of ES training (20 shock presentations; 0.5 mA; 5.0 s maximum duration; 1.0 min interstimulus interval). Five days later, they were re-exposed to the shock context. Following shock training, REM was significantly increased in both light and dark periods. Non-REM (NREM) and total sleep (TS) duration were decreased during the light period. Similar effects on REM and NREM were observed following re-exposure to the training context alone. Microinjections of saline into CNA immediately following ES also produced similar increases in REM, whereas microinjections of muscimol (MUS; GABAA (γ-aminobutyric acid) antagonist) subsequent to ES blocked the increases in REM. These data, along with previous work with ES and IS, demonstrate that stressor controllability is important in determining how stress impacts sleep. Moreover, the results of the microinjection study indicate that the effects of ES on REM are regulated through the CNA.

Effects of environmental and pharmacological manipulations on cocaine-vs-negative reinforcer choice in male and female rats.

The adverse consequences of human addictive drug use could be the result of either addictive drug consumption resulting in punishment (e.g., incarceration) or failure to engage in negative-reinforced behaviors that might compete with drug-maintained behaviors (e.g., contingency management strategies that reset payment amounts for drug free urines). The goal of the present study was to establish a discrete-trial cocaine-vs-negative reinforcer (SNR) choice procedure where rats were presented with a simplified model of this conflict: choose negative reinforcement (i.e., escape or avoid foot shock) or choose an intravenous (IV) cocaine infusion followed by an inescapable shock. Responding was maintained in male and female rats by IV cocaine infusions (0.32-1.8 mg/kg/inf) and a SNR (0.1-0.7 mA shock) under a discrete-trial concurrent"choice" schedule during daily sessions. Following parametric reinforcer magnitude and response requirement experiments, the effects of 12 h extended access cocaine self-administration and acute diazepam (0.32-10 mg/kg, IP) pretreatment were determined on cocaine-vs-SNR choice. Negative reinforcement was chosen over all cocaine doses. Lowering shock magnitude or increasing SNR response requirement failed to promote behavioral reallocation towards cocaine. Extended access cocaine self-administration sessions resulted in high daily cocaine intakes but failed to significantly increase cocaine choice in all (19) but one rat. Acute diazepam pretreatment also did not alter choice behavior up to doses that produced behavioral depression. These results suggest that SNRs may be a source of reinforcement that effectively compete with and mitigate maladaptive addictive drug-maintained behaviors in the general population.

Pharmacological Evaluation of Benincasa Hispida Cogn. Fruit on Chronic Foot Shock Induced Stress in Mice

Stress can be defined as a brain-body reaction towards stimuli arising from the environment or from internal cues that are interpreted as a disruption of homeostasis. A number of reports indicated that treatment with herbal plant extracts could lead to a significant reduction in stress. The aim of this study was to evaluate the antistress activity through Inescapable electric chronic foot shock model in mice and to assess the effect of extract on stress induced behavioral changes in animals and to determine the efficiency of Benincasa hispida Cogn. Extract on Motor activity and Elevated plus maze to assess anxiety. In this study, mice were divided into five groups with five animals each. The first group received ip dose of the vehicle saline (2ml/kg). The second group received diazepam 1mg/kg ip along with foot shock. Third, fourth, and fifth groups received oral dose of 100, 200, and 400 mg /kg of fruit extract of Benincasa hispida along with foot shock. Inescapable electricFoot-shocks (intensity 0.8mA, interval: 10sec, duration:10sec) were delivered through a grid floor once daily for 21 days. The results showed that Benincasa hispida extract (200 and 400mg/kg) was found to have an antistress effect. The dose of Benincasa hispida extract (200 and 400mg/kg), increased entries into open arm and the time spend in open arm on the elevated plus maze test indicate that extract reduced the stress level and it significantly reduced the spontaneous motor activity and decreased the anxiety. The results suggest that the ethanolic extract of Benincasa hispida has potential antistress effect that can be explored for therapeutic advantage as an alternative treatment in medical conditions.

Effects of PTSD-Dependent Neurogenic Hypertension and Inflammation on Thoracic Aortic Wall Homeostasis

Objective: Post-traumatic stress disorder (PTSD) in patients is associated with hypertension, increased heart rate, and elevated plasma proinflammatory cytokines, which also are risk factors for the development of cardiovascular conditions, such as thoracic aortic aneurysm (TAA). Although the association between stress and aortic pathology has been suggested, the exact mechanism linking the two is unknown. Our hypothesis is that PTSD-induced changes in mechanical and inflammatory signaling alter thoracic aortic wall homeostasis, which can predispose to aortic disease. Methods: Adult male and female C57BL/6 mice (n=7) underwent PTSD induction consisting of inescapable foot shock (five x 1 sec, 1 mA foot shocks over 6 min paired with a 20 sec 80 db tone (conditioned stimulus)) followed by single prolonged stress events. Mice were subjected to behavioral testing at 4-week intervals over a 16-week paradigm to determine their PTSD-like phenotype. The behavioral tests were chosen to assess for each of the human criteria of PTSD based on the DSM-5. A composite t-score was generated for each mouse derived from their mean individual z-score for each parameter, of each behavioral test. Mice with a composite t-score above 1.96 were considered to have a PTSD-like phenotype. Blood pressure was measured (CODA, tail-cuff) at baseline and at 4-week intervals. At terminal study, thoracic aortic diameter was measured by digital microscopy. Plasma was collected to measure circulating cytokines and aortic tissue was harvested for biochemistry and histology. Aortic structure was examined for changes in elastic lamellae, collagen deposition, and cellular content. Control mice (n=8) underwent the same procedures except for PTSD induction. Results: Our protocol generated a PTSD-like phenotype in 71% (5 of 7) of the mice. PTSD mice had significantly higher systolic blood pressures following a conditioned stimulus (PTSD (n=5), 153 ± 8mmHg; control (n=8), 129 ± 7mmHg, p<0.05). PTSD mice also had increased plasma proinflammatory cytokines (IL1-α, IL-3, IL-5, IL-7, IL-9, all p<0.05), enhanced extracellular matrix remodeling (ECM), and larger aortic diameters than control mice (PTSD (n=5), 712.9 ± 97.6μm; control (n=8), 584.2 ± 102.7μm, p <0.05). Conclusion: Our PTSD-like mouse model recapitulated the human phenotype showing elevated systolic blood pressure and increased circulating proinflammatory cytokines. Increase thoracic aortic diameter and changes in the ECM suggest that PTSD can alter structural homeostasis in the aortic wall, predisposing the thoracic aorta to development of further pathology. Future studies will examine PTSD effects on TAA progression in a mouse model. NIH-NCATS TL1 TR00145-08 & UL1TR001450-08 (HH) and VA Merit Award I01-BX000904-08A1 (JAJ) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

340 The Effects of PTSD-Dependent Neurogenic Hypertension and Inflammation on Thoracic Aortic Aneurysm Progression

OBJECTIVES/GOALS: Nearly all thoracic aortic aneurysm patients suffer from hypertension leading to elevated wall tension and abnormal extracellular matrix remodeling. PTSD patients have higher blood pressure both at rest and in response to stimuli. Although stress is associated with cardiovascular disease, the exact mechanism linking the two is still unknown. METHODS/STUDY POPULATION: Adult C57BL/6 mice underwent a PTSD induction protocol consisting of inescapable foot shock followed by single prolonged stress. The mice were assessed incrementally for their PTSD-like phenotype using specific behavioral tests chosen to assess for each of the human criteria of PTSD according to the DSM-V. Tail cuff blood pressure measurements were taken serially throughout the 16-week protocol. At terminal study, thoracic aortic diameter measurements were obtained through digital microscopy and plasma was harvested for cytokine analysis. Thoracic aortic aneurysms (TAA) were induced through periadventitial application of a calcium chloride solution on the descending thoracic aorta in BPH/2J and BPN/3J adult mice. The thoracic aortic diameter was measured at terminal study through digital microscopy. RESULTS/ANTICIPATED RESULTS: Using our PTSD-like mouse model we have demonstrated that PTSD-like mice have significantly higher systolic blood pressure following a reminder of the traumatic event than control mice recapitulating the human phenotype. They also had increased plasma proinflammatory cytokines and larger thoracic aortic diameters than control mice. Although the increased thoracic aortic diameter is not an aneurysm, it suggests ECM remodeling is occurring predisposing the aorta to aneurysm formation. Finally, we have shown that in neurogenic hypertensive mice, TAA formation was accelerated by 12 weeks with roughly 70% dilation at 4 weeks post-TAA induction surgery as compared to roughly a 20% dilation in control mice. DISCUSSION/SIGNIFICANCE: Altogether, these studies reinforce the link between stress and TAA development, and our mouse model will allow for the underlying mechanism to be elucidated. Better understanding of the mechanism linking PTSD and TAA will allow for the creation of novel therapeutics to treat PTSD symptoms while also delaying TAA progression.

Abnormal compositions of gut microbiota and metabolites are associated with susceptibility versus resilience in rats to inescapable electric stress

BackgroundIncreasing evidence suggests the role of gut microbiota in resilience versus vulnerability after stress. However, the role of gut microbiota and microbiome-derived metabolites in resilience versus susceptibility in rodents exposed to stress remains unclear. MethodsAdult male rats were exposed to inescapable electric stress under the learned helplessness (LH) paradigm. The composition of gut microbiota and metabolites in the brain and blood from control (no stress) rats, LH resilient rats, and LH susceptible rats were examined. ResultsAt the genus level, the relative abundances of Asaccharobacter, Eisenbergiella, and Klebsiella in LH susceptible rats were significantly higher than that of LH resilient rats. At the species level, the relative abundances of several microbiome were significantly altered between LH susceptible rats and LH resilient rats. Furthermore, there were several metabolites in the brain and blood altered between LH susceptible rats and LH resilient rats. A network analysis showed correlations between the abundance of several microbiome and metabolites in the brain (or blood). LimitationsDetailed roles of microbiome and metabolites are unclear. ConclusionsThese findings suggest that abnormal compositions of the gut microbiota and metabolites might contribute to susceptibility versus resilience in rats subjected to inescapable electric foot shock.

Synergistic effects of combined therapy with cerebrolysin and enriched environment on anxiety-like behavior and spatial cognitive deficits in posttraumatic stress disorder-like mouse model.

Posttraumatic stress disorder (PTSD) is a serious neuropsychiatric disorder that occurs after exposure to stressful, fearful, or troubling events. Cerebrolysin (CBL), consists of low molecular weights neurotrophic factors and amino acids obtained from purified porcine brain proteins. This study aimed to evaluate the possible therapeutic effects of enriched environment (EE) and CBL alone or combined for reducing anxiety and cognitive deficits in PTSD-like mouse models. For this purpose, inescapable electric foot shocks were delivered to Balb/c mice for two consecutive days. Then mice were treated with CBL (2.5 mL/kg) and/or were kept in EE (2 h per day) or received their combination for 14 consecutive days. The hole-board test and Lashley III paradigm were used to assess anxiety and spatial learning and memory, respectively. Changes in the serum corticosterone level and expression of synaptic elements, including; growth-associated protein 43, post-synaptic density 95, and synaptophysin were assessed in the hippocampus. This model caused anxiety and spatial memory impairment associated with increased serum corticosterone levels and decreased synaptic elements. Nevertheless, CBL and/or combination treatment could reverse behavioral and molecular alterations. Our findings indicated that CBL, separately or in combination with EE, is effective in reducing anxiety and spatial memory impairment in PTSD-like mice.

Effects of Semax in the Models of Acute Stress

Acute stress exposure causes a cascade of neurochemical reactions, leading, in particular, to a change in behavior and increased tolerance to pain in humans and animals. ACTH/MSH-like peptides play an important role in regulating the body’s response to stressful exposures. The aim of the present study was to assess the effects of the ACTH4–10 analogue heptapeptide Semax in various models of acute stress. The effect of intraperitoneal Semax administration at doses of 0.05 and 0.5 mg/kg on changes in behavior and pain sensitivity of Wistar rats in models of inescapable intermittent foot shock stress and forced cold-water swim stress was investigated. To assess the involvement of the endogenous opioid system in the effects of stress, an impact of pretreatment with opioid receptor antagonist naloxone (1 mg/kg) was studied. The stressors used led to an increase in the pain threshold in the paw-pressure test, which indicates the development of stress-induced analgesia (SIA). In addition, rats exposed to stress had an decrease in exploratory behavior and an increase in the anxiety-like behavior in the hole board test. Both Semax and naloxone attenuated SIA in the model of inescapable foot shock stress, but did not affect the value of the pain threshold in the model of forced cold swim stress. Both studied drugs did not affect the behavior of rats in the models of acute stress used. It can be concluded that Semax blocks the opioid form of stress-induced analgesia, but does not affect the behavioral alterations in rats exposed to acute stress.

Photobiomodulation attenuates oligodendrocyte dysfunction and prevents adverse neurological consequences in a rat model of early life adversity.

Rationale: Adverse experiences in early life including abuse, trauma and neglect, have been linked to poor physical and mental health outcomes. Emerging evidence implies that those who experienced early life adversity (ELA) are more likely to develop cognitive dysfunction and depressive-like symptoms in adulthood. The molecular mechanisms responsible for the negative consequences of ELA, however, remain unclear. In the absence of effective management options, anticipatory guidance is the mainstay of ELA prevention. Furthermore, there is no available treatment that prevents or alleviates the neurologic sequelae of ELA, especially traumatic stress. Hence, the present study aims to investigate the mechanisms for these associations and evaluate whether photobiomodulation (PBM), a non-invasive therapeutic procedure, can prevent the negative cognitive and behavioral manifestations of ELA in later life. Methods: ELA was induced by repeated inescapable electric foot shock of rats from postnatal day 21 to 26. On the day immediately following the last foot shock, 2-min daily PBM treatment was applied transcranially for 7 consecutive days. Cognitive dysfunction and depression-like behaviors were measured by a battery of behavioral tests in adulthood. Subsequently, oligodendrocyte progenitor cells (OPCs) differentiation, the proliferation and apoptosis of oligodendrocyte lineage cells (OLs), mature oligodendrocyte, myelinating oligodendrocyte, the level of oxidative damage, reactive oxygen species (ROS) and total antioxidant capacity were measured and analyzed using immunofluorescence staining, capillary-based immunoassay (ProteinSimple®) and antioxidant assay kit. Results: The rats exposed to ELA exhibited obvious oligodendrocyte dysfunction, including a reduction in OPCs differentiation, diminished generation and survival of OLs, decreased OLs, and decreased matured oligodendrocyte. Furthermore, a deficit in myelinating oligodendrocytes was observed, in conjunction with an imbalance in redox homeostasis and accumulated oxidative damage. These alternations were concomitant with cognitive dysfunction and depression-like behaviors. Importantly, we found that early PBM treatment largely prevented these pathologies and reversed the neurologic sequelae resulting from ELA. Conclusions: Collectively, these findings provide new insights into the mechanism by which ELA affects neurological outcomes. Moreover, our findings support that PBM may be a promising strategy to prevent ELA-induced neurologic sequelae that develops later in life.

Aberrant ventral dentate gyrus structure and function in trauma susceptible mice

Post-traumatic stress disorder (PTSD) is a psychiatric disorder vulnerable individuals can develop following a traumatic event, whereas others are resilient. Enhanced insight into the mechanistic underpinnings contributing to these inter-individual differences in trauma susceptibility is key to improved treatment and prevention. Aberrant function of the hippocampal dentate gyrus (DG) may contribute to its psychopathology, with the dorsal DG potentially encoding trauma memory generalization and the ventral DG anxiety. Using a mouse model, we hypothesized that susceptibility to develop PTSD-like symptoms following trauma will be underpinned by aberrant DG structure and function. Mice were exposed to a traumatic event (unpredictable, inescapable foot shocks) and tested for PTSD-like symptomatology following recovery. In four independent experiments, DG neuronal morphology, synaptic protein gene and protein expression, and neuronal activity during trauma encoding and recall were assessed. Behaviorally, trauma-susceptible animals displayed increased anxiety-like behavior already prior to trauma, increased novelty-induced freezing, but no clear differences in remote trauma memory recall. Comparison of the ventral DG of trauma susceptible vs resilient mice revealed lower spine density, reduced expression of the postsynaptic protein homer1b/c gene and protein, a larger population of neurons active during trauma encoding, and a greater presence of somatostatin neurons. In contrast, the dorsal DG of trauma-susceptible animals did not differ in terms of spine density or gene expression but displayed more active neurons during trauma encoding and a lower amount of somatostatin neurons. Collectively, we here report on specific structural and functional changes in the ventral DG in trauma susceptible male mice.

A Protocol for the Induction of Posttraumatic Stress-Disorder (PTSD)-like Behavior in Mice.

Post-traumatic stress disorder (PTSD) is a debilitating psychiatric condition that precipitates in ~10% of individuals exposed to a traumatic event (TE). Symptoms include recurrent and intrusive thoughts, sleep disturbance, hypervigilance, exaggerated startle, and reckless or destructive behavior. Given the complex and heterogeneous nature of the disease, animal models for PTSD-like symptomatology are of increasing interest to the field of PTSD research. Because resilience to PTSD-like symptomatology is an important epidemiologic aspect of PTSD, animal models that resolve vulnerable and resilient animals are of particular value. Due to the complex nature of the PTSD phenotype and the potential overlaps between PTSD-like behavior and behaviors associated with other stress-induced psychopathologies such as anxiety or depression, animal models that utilize multiple readouts for PTSD-like behavior are also of increasing value. We utilize a paradigm developed by Lebow et al. 2012 for the induction and identification of PTSD-like symptomatology in mice. This paradigm utilizes inescapable electric foot shock, administered in two decontextualized sessions over two consecutive days. Stressed mice perform four behavioral tests - dark/light transfer, marble burying, acoustic startle, and home cage activity - to generate five behavioral readouts of PTSD-like behavior: % risk assessment (%RA), % marbles buried (%MB), % prepulse inhibition (%PPI), latency to peak startle amplitude (LPSA), and % light phase activity (%LPA). PTSD-like symptomatology is characterized by decreased %RA, increased %MB, decreased %PPI, decreased LPSA, and increased %LPA. The 20% of animals displaying the most PTSD-like behavior in each test are awarded a certain number of points depending on the test, and animals scoring sufficient points are designated as PTSD-like, while animals scoring no points are designated PTSD-resilient. This paradigm identifies PTSD-like behavior in ~15% of animals, a rate comparable to that observed in humans. This protocol represents a robust and reproducible paradigm for the induction of PTSD-like behavior in mice.