Midazolam ameliorates the behavior deficits of a rat posttraumatic stress disorder model through dual 18 kDa translocator protein and central benzodiazepine receptor and neurosteroidogenesis

Chlorogenic acid improves SPS-induced PTSD-like behaviors in rats by regulating the crosstalk between Nrf2 and NF-κB signaling pathway

Post-traumatic stress disorder (PTSD) is a long-term delayed mental disorder caused by sudden, threatening or catastrophic life events. Chlorogenic acid (CGA) is a polyphenolic acid rich in Eucommia ulmoides and other plants with potential neuroprotective effects, effectively enhances learning and memory, and exerts a beneficial impact on improving mood and attention. However, the effects and mechanisms of CGA on PTSD-like behaviors remain uncertain. This study is to explore the effects and mechanisms of CGA on PTSD by using network pharmacology analysis, molecular docking and experimental validation, and try to provide new strategies for the treatment of PTSD. The results indicated that 9 core targets with a strong binding affinity with CGA were screened out, and they were mainly enriched in apoptosis, inflammation, and oxidative stress. The followed vivo experiments indicated that CGA could alleviate single prolonged stress (SPS)-induced PTSD-like behaviors, and improve hippocampal pathological damage, apoptosis and synaptic plasticity through antioxidant and anti-inflammatory effects by regulating Nrf2 and NF-κB pathways. Thus, CGA may inhibit hippocampal neuronal apoptosis, reduce neuroinflammatory and oxdiative stress response, and enhance hippocampal synaptic plasticity through regulating the crosstalk between Nrf2 and NF-κB signaling pathway, thereby improving SPS-induced PTSD-like behaviors.

Phyllanthus niruri L. Administration during pregnancy and breastfeeding: Maternal evaluation and effects on initial development and adult behavior of male rat offspring

The leaves of Phyllanthus niruri L. are used in folk medicine in many countries to treat various diseases. However, despite the enormous therapeutic potential, use of the plant is contraindicated during pregnancy and breastfeeding. Reports on the impacts of exposure to this plant on the development of the offspring of rats are still scarce and controversial. The aim of this study is to evaluate the effects of the administration of P. niruri aqueous extract, during pregnancy and lactation, on maternal toxicity, on postnatal physical development, and on behavioral aspects in adult male offspring. Pregnant rats were divided into three experimental groups (n = 8/group) and treated daily during pregnancy and lactation, (gavage), with vehicle and doses of 75 and 150 mg/kg of aqueous extract of P. niruri. To assess maternal toxicity; weight gain, feed intake, reproductive outcomes, and biochemical profiles were analyzed. The male pups were evaluated for physical development through the end of lactation and submitted to tests evaluating their behavior in adulthood. Treatment with the aqueous extract of P. niruri (AEPN) did not cause significant changes in the maternal and reproductive parameters analyzed. However, changes in the biochemical markers of liver function were observed. In the male offspring, the extract did not alter postnatal physical growth, but caused early opening of the ear canal and eyes. In the evaluation of adult male offspring, it was found that the groups exposed to AEPN presented behavioral changes predictive of anxiolytic effect. Brain malondialdehyde levels of male offspring whose mothers were treated with AEPN were significantly reduced. Our results demonstrate that exposure to P. niruri extract did not induce significant changes sufficiently to indicate occurrence of maternal or postnatal toxicity. In addition, in the male offspring exposed to the extract, anticipation of physical maturation parameters and anxiolytic-like behavior was observed.

Factors impacting prazosin efficacy for nightmares and insomnia in PTSD patients - a systematic review and meta-regression analysis

Posttraumatic stress disorder (PTSD) is a debilitating condition affecting 5.7 % of the global population in their lifetime. There is a strong association between trauma-related nightmares and insomnia with higher rates of physical illness, mental distress, and suicide among PTSD patients. Prazosin, an α1-adrenergic antagonist, has shown mixed results in treating these sleep disturbances. This study aims to evaluate the effect of prazosin compared to placebo on insomnia, nightmares, and global PTSD symptoms, and to examine variables that might influence this effect. We conducted a meta-analysis and a novel meta-regression analysis of randomized clinical trials (RCTs) comparing prazosin to placebo in samples of patients with PTSD. Data sources were MEDLINE, EMBASE, Scopus, ISI Web of Science, and PTSD Pubs. Examined variables were age, gender, military/civilian status, prazosin dose, treatment duration, baseline symptom severity, use of antidepressants, use of benzodiazepines (BDZ), prevalence of depression, and alcohol use disorder. Ten RCTs with 648 patients were included. Analysis revealed prazosin significantly improved insomnia (SMD = -0.654, p = 0.043) and nightmares (SMD = -0.641, p = 0.025), but not overall PTSD symptoms (SMD = -0.428, p = 0.077). Unexpectedly, higher BDZ use was associated with greater improvement in insomnia (β = -0.046; p = 0.01) and PTSD severity (β = -0.037; p = 0.004). These findings suggest that prazosin effectively reduces insomnia and nightmares in PTSD patients. Benzodiazepine co-administration seems to enhance prazosin's efficacy, suggesting that the addition of prazosin might allow for a reduction of BDZ doses in these patients. Further research should empirically test the efficacy of prazosin alone versus prazosin combined with BDZ to confirm these findings.

The ameliorative effect of midazolam on empathy-like behavior in old rats

Although studies suggest that cognitive functions in the elderly are impaired, elderly people tend to be more successful and wiser in solving emotional problems. In empathy-like behavior models, the observer rat rescues the distressed cage mate by displaying emotional and cognitive ability. The aim of the study was to investigate the changes in empathy-like behavior in older rats in comparison to adult rats. In addition, we wanted to determine the effects of alterations in neurochemicals (such as corticosterone, oxytocin, vasopressin, and their receptor levels) and emotional situations on this behavior. In our study, we initially completed empathy-like behavior tests and emotional tests (open field, elevated plus maze) and performed neurochemical examinations in the serum and brain tissues. In the second step of research, we applied a midazolam (benzodiazepine) treatment to examine the effect of anxiety on empathy-like behavior. In the old rats, we observed that empathy-like behavior deteriorated, and anxiety signs were more pronounced. We detected a positive correlation between the latency in empathy-like behavior and corticosterone levels and v1b receptor levels. The midazolam effect on empathy-like behavior was attenuated by flumazenil (a benzodiazepine receptor antagonist). The recordings of ultrasonic vocalization showed frequencies around 50 kHz emitted by the observer and this was associated with the expectation of social contact. Our results state that compared to adult rats, old rats were more concerned and failed during empathy-like behavior. Midazolam may improve this behavior by anxiolysis.

The effect of SSRIs on fear learning: a systematic review and meta-analysis

RATIONALE

Selective serotonin reuptake inhibitors (SSRIs) are considered first-line medication for anxiety-like disorders such as panic disorder, generalized anxiety disorder, and post-traumatic stress disorder. Fear learning plays an important role in the development and treatment of these disorders. Yet, the effect of SSRIs on fear learning are not well known.

OBJECTIVE

We aimed to systematically review the effect of six clinically effective SSRIs on acquisition, expression, and extinction of cued and contextual conditioned fear.

METHODS

We searched the Medline and Embase databases, which yielded 128 articles that met the inclusion criteria and reported on 9 human and 275 animal experiments.

RESULTS

Meta-analysis showed that SSRIs significantly reduced contextual fear expression and facilitated extinction learning to cue. Bayesian-regularized meta-regression further suggested that chronic treatment exerts a stronger anxiolytic effect on cued fear expression than acute treatment. Type of SSRI, species, disease-induction model, and type of anxiety test used did not seem to moderate the effect of SSRIs. The number of studies was relatively small, the level of heterogeneity was high, and publication bias has likely occurred which may have resulted in an overestimation of the overall effect sizes.

CONCLUSIONS

This review suggests that the efficacy of SSRIs may be related to their effects on contextual fear expression and extinction to cue, rather than fear acquisition. However, these effects of SSRIs may be due to a more general inhibition of fear-related emotions. Therefore, additional meta-analyses on the effects of SSRIs on unconditioned fear responses may provide further insight into the actions of SSRIs.

Sex differences in acetylcholinesterase modulation during spatial and fear memory extinction in the amygdala; an animal study in the single prolonged stress model of PTSD

Background and purpose

Men and women show different reactions to trauma and that is believed to be the reason behind the higher prevalence of post-traumatic stress disorder (PTSD) in women. Cholinergic signaling has long been known to be involved in the processing of fear-related information and the amygdala is a critical center for fear modulation. The main goal of the current research was to find (a) whether trauma results in different learning/extinction of fear or spatial-related information among male and female rats and (b) if trauma is associated with different acetylcholinesterase (AchE) activity in the amygdala.

Experimental approach

We used single prolonged stress (SPS) as a PTSD model in this study. Normal and SPS animals of both sexes were tested in contextual and spatial tasks (learning and extinction). AchE activity in the amygdala was also measured during each process.

Findings / Results

Results indicated that fear and spatial learning were impaired in SPS animals. SPS animals also had deficits in fear and spatial memory extinction and the effect was significantly higher in female- SPS than in the male-SPS group. In the enzymatic tests, AchE activity was increased during the fear extinction test and incremental changes were more significant in the female-SPS group.

Conclusion and implications

Collectively, these findings provided evidence that sex differences in response to trauma were at least partly related to less fear extinction potential in female subjects. It also indicated that the extinction deficit was associated with reduced cholinergic activity in the amygdala of female animals.

Intra-mPFC injection of sodium butyrate promotes BDNF expression and ameliorates extinction recall impairment in an experimental paradigm of post-traumatic stress disorder

Objectives

Therapeutic strategies that facilitate extinction are promising in the treatment of post-traumatic stress disorder (PTSD). Brain-derived neurotrophic factor (BDNF) has a crucial role in neural plasticity, a process needed for the retention of fear extinction. In this study, we investigated the effects of local administration of a histone deacetylase (HDAC) inhibitor, sodium butyrate (NaBu), on BDNF transcription and behavioral markers of extinction in the single prolonged stress (SPS) model of PTSD.

Materials and Methods

NaBu was infused into the infralimbic (IL) subregion of the medial prefrontal cortex (mPFC) of male rats. The freezing response was recorded as the criterion to assess fear strength on the day of extinction as well as 24 hr later in the retention test. Other behavioral tests were also measured to evaluate the anxiety level, locomotor activity, and working memory on the retention day. HDAC activity and BDNF mRNA expression were evaluated after the behavioral experiments.

Results

NaBu facilitated the recall of fear extinction in SPS rats (P<0.0001). SPS rats had higher HDAC activity (P<0.0001) and lower BDNF expression (P<0.05) than non-SPS animals. Also, anxiety was higher in the SPS group (P<0.0001), but locomotor activity (P=0.61) and working memory (P=0.36) were not different between SPS and Non-SPS groups.

Conclusion

Our findings provide evidence that the mechanism of action of NaBu in the improvement of extinction recall is mediated, in part, by enhancing histone acetylation and reviving BDNF expression in IL.

Pharmacological strategies for post-traumatic stress disorder (PTSD): From animal to clinical studies

Post-traumatic stress disorder (PTSD) is a disabling psychiatric condition with a critical familiar, personal, and social impact. Patients diagnosed with PTSD show various symptoms, including anxiety, depression, psychotic episodes, and sleep disturbances, complicating their therapeutic management. Only sertraline and paroxetine, two selective serotonin reuptake inhibitors, are approved by different international agencies to treat PTSD. In addition, these drugs are generally combined with psychotherapy to achieve positive results. However, these pharmacological strategies present limited efficacy. Nearly half of the PTSD patients do not experience remission of symptoms, possibly due to the high prevalence of psychiatric comorbidities. Therefore, in clinical practice, other off-label medications are common, even though the effectiveness of these drugs needs to be further investigated. In this line, antipsychotics, antiepileptics, adrenergic blockers, benzodiazepines, and other emerging pharmacological agents have aroused interest as potential therapeutic tools to improve some specific symptoms of PTSD. Thus, this review is focused on the most widely used drugs for the pharmacological treatment of PTSD with a translational approach, including clinical and preclinical studies, to emphasize the need to develop safer and more effective medications.

Translocator protein (18kDa) TSPO: a new diagnostic or therapeutic target for stress-related disorders?

Efficient treatment of stress-related disorders, such as depression, is still a major challenge. The onset of antidepressant drug action is generally quite slow, while the anxiolytic action of benzodiazepines is considerably faster. However, their long-term use is impaired by tolerance development, abuse liability and cognitive impairment. Benzodiazepines act as positive allosteric modulators of ɣ-aminobutyric acid type A (GABA_A) receptors. 3α-reduced neurosteroids such as allopregnanolone also are positive allosteric GABA_A receptor modulators, however, through a site different from that targeted by benzodiazepines. Recently, the administration of neurosteroids such as brexanolone or zuranolone has been shown to rapidly ameliorate symptoms in post-partum depression or major depressive disorder. An attractive alternative to the administration of exogenous neurosteroids is promoting endogenous neurosteroidogenesis via the translocator protein 18k Da (TSPO). TSPO is a transmembrane protein located primarily in mitochondria, which mediates numerous biological functions, e.g., steroidogenesis and mitochondrial bioenergetics. TSPO ligands have been used in positron emission tomography (PET) studies as putative markers of microglia activation and neuroinflammation in stress-related disorders. Moreover, TSPO ligands have been shown to modulate neuroplasticity and to elicit antidepressant and anxiolytic therapeutic effects in animals and humans. As such, TSPO may open new avenues for understanding the pathophysiology of stress-related disorders and for the development of novel treatment options.

Allopregnanolone: An overview on its synthesis and effects

Allopregnanolone, a 3α,5α-progesterone metabolite, acts as a potent allosteric modulator of the γ-aminobutyric acid type A receptor. In the present review, the synthesis of this neuroactive steroid occurring in the nervous system is discussed with respect to physiological and pathological conditions. In addition, its physiological and neuroprotective effects are also reported. Interestingly, the levels of this neuroactive steroid, as well as its effects, are sex-dimorphic, suggesting a possible gender medicine based on this neuroactive steroid for neurological disorders. However, allopregnanolone presents low bioavailability and extensive hepatic metabolism, limiting its use as a drug. Therefore, synthetic analogues or a different therapeutic strategy able to increase allopregnanolone levels have been proposed to overcome any pharmacokinetic issues.

A network pharmacology study with molecular docking to investigate the possibility of licorice against posttraumatic stress disorder

Post traumatic stress disorder (PTSD) is a mental health condition that has a debilitating effect on a person's quality of life and leads to a high socioeconomic burden. Licorice has been demonstrated to have neuroprotective and antidepressant-like effects, but little is known about its effects for the treatment of PTSD. The present study aimed to explore the potential of licorice for PTSD therapy using a network pharmacology approach with molecular docking studies. The compounds of licorice were obtained from databases with screening by absorption, distribution, metabolism and excretion (ADME) evaluation. Genes associated with compounds or PTSD were obtained from public databases, and the genes overlapping between licorice compounds and PTSD were compared by Venn diagram. A network of medicine-ingredients-targets-disease was constructed, visualized, and analyzed using cytoscape software. Protein-protein interactions, gene ontology, pathway enrichment and molecular docking were performed to evaluate the effect of licorice for the treatment of PTSD. 69 potential compounds were screened after ADME evaluation. A total of 81 compound-related genes and 566 PTSD-related genes were identified in the databases with 27 overlapping genes. Licorice compounds (e.g., medicarpin, 7-methoxy-2-methyl isoflavone, shinpterocarpin, formononetin, licochalcone a) and target proteins (e.g., ESR1, PTGS2, NOS2, and ADRB2) with high degree in the network were involved in G protein-coupled receptor signaling pathways at the postsynaptic/synaptic membrane. Moreover, neuroactive ligand-receptor interactions, calcium signaling, cholinergic synapse, serotonergic synapse and adrenergic signaling in cardiomyocytes may play important roles in the treatment of PTSD by licorice. This study provides molecular evidence of the beneficial effects of licorice for the treatment of PTSD.

Antidepressant-like effects of Z-ligustilide on chronic unpredictable mild stress-induced depression in rats

Depression is a significant public health issue and its neuropathogenesis is associated with the dysfunction of progesterone and allopregnanolone biosynthesis. Z-ligustilide (LIG), one of the main components of the herb Angelica sinensis (Oliv.) Diels (AS), is reported to have antidepressant activities. The present study aimed to evaluate the antidepressant-like effects of LIG via behavioral tests and to measure the levels of progesterone and allopregnanolone in the prefrontal cortex and hippocampus. The results demonstrated that LIG (20 and 40 mg/kg) exerted antidepressant-like effects, confirmed by increased mobility, locomotion, rearing frequency and preference to sucrose. Furthermore, the levels of progesterone and allopregnanolone in the prefrontal cortex and hippocampus were markedly increased following treatment with LIG (20 and 40 mg/kg), indicating that both neurosteroids could serve a significant role in the antidepressant-like effects of LIG.

Systematic Review and Methodological Considerations for the Use of Single Prolonged Stress and Fear Extinction Retention in Rodents

Posttraumatic stress disorder (PTSD) is a mental health condition triggered by experiencing or witnessing a terrifying event that can lead to lifelong burden that increases mortality and adverse health outcomes. Yet, no new treatments have reached the market in two decades. Thus, screening potential interventions for PTSD is of high priority. Animal models often serve as a critical translational tool to bring new therapeutics from bench to bedside. However, the lack of concordance of some human clinical trial outcomes with preclinical animal efficacy findings has led to a questioning of the methods of how animal studies are conducted and translational validity established. Thus, we conducted a systematic review to determine methodological variability in studies that applied a prominent animal model of trauma-like stress, single prolonged stress (SPS). The SPS model has been utilized to evaluate a myriad of PTSD-relevant outcomes including extinction retention. Rodents exposed to SPS express an extinction retention deficit, a phenotype identified in humans with PTSD, in which fear memory is aberrantly retained after fear memory extinction. The current systematic review examines methodological variation across all phases of the SPS paradigm, as well as strategies for behavioral coding, data processing, statistical approach, and the depiction of data. Solutions for key challenges and sources of variation within these domains are discussed. In response to methodological variation in SPS studies, an expert panel was convened to generate methodological considerations to guide researchers in the application of SPS and the evaluation of extinction retention as a test for a PTSD-like phenotype. Many of these guidelines are applicable to all rodent paradigms developed to model trauma effects or learned fear processes relevant to PTSD, and not limited to SPS. Efforts toward optimizing preclinical model application are essential for enhancing the reproducibility and translational validity of preclinical findings, and should be conducted for all preclinical psychiatric research models.

Effects of Selective Serotonin Reuptake Inhibitors on Depression-Like Behavior in a Laser-Induced Shock Wave Model

Primary blast injury can result in depression-like behavior in the long-term. However, the effects of the selective serotonin reuptake inhibitor (SSRI) on the depression induced by mild blast traumatic brain injury (bTBI) in the long-term remain unclear. We generated a mouse model of mild bTBI using laser-induced shock wave (LISW) and administered an SSRI to mice by oral gavage for 14 days after LISW exposure. This study aimed to investigate the mechanisms of SSRI-mediated alleviation of depression-like behavior induced by mild bTBI. Animals were divided into three groups: sham, LISW-Vehicle, and LISW-SSRI. LISW was applied to the head of anesthetized mice at 0.5 J/cm². Twenty-eight days after the LISW, mice in the LISW-SSRI group exhibited reduced depression-like behavior, a significant increase in the number of cells co-stained for 5-bromo-2'-deoxyuridine (Brd-U) and doublecortin (DCX) in the dentate gyrus (DG) as well as increased brain-derived neurotrophic factor (BDNF) and serotonin levels in the hippocampus compared to the sham and LISW-Vehicle groups. Additionally, levels of phosphorylated cAMP response element binding protein (pCREB) in the DG were significantly decreased in the LISW-Vehicle group compared to that in the sham group. Importantly, pCREB levels were not significantly different between LISW-SSRI and sham groups suggesting that SSRI treatment may limit the downregulation of pCREB induced by mild bTBI. In conclusion, recovery from depression-like behavior after mild bTBI may be mediated by hippocampal neurogenesis induced by increased BDNF and serotonin levels as well as the inhibition of pCREB downregulation in the hippocampus.

Sex-divergent long-term effects of single prolonged stress in adult rats

Single prolonged stress (SPS) is an experimental model that recapitulates in rodents some of the core symptoms of post-traumatic stress disorder (PTSD). Although women have a two-fold greater risk to develop PTSD, most preclinical studies have been carried out in males. Furthermore, the long-term effects of behavioral alterations induced by SPS have been rarely investigated. Here, we evaluated the long-term effects of SPS on PTSD-relevant behavioral domains in rats and whether these effects were sex-dependent. To this aim, separate cohorts of male and female adult rats were subjected to SPS and, 30 days later, long-term effects were assessed. We found that SPS exposure reduced locomotor activity in both sexes in an open field task. Males only showed increased anxiety-like behavior in the elevated plus maze and marble burying tests, enhanced acoustic startle response and impaired spatial memory retention while females were unaffected. SPS exposure did not alter auditory fear memory dynamics in males, but it did alter extinction retrieval in females. We provide the first evidence that SPS reproduces long-term emotional alterations in male, but not in female, rats which were observed 30 days following trauma exposure, thus resembling some of the hallmark symptoms of PTSD. Furthermore, our results show for the first time a long-term SPS-induced alteration of cued fear extinction in females. Our findings are relevant to future research on trauma-related disorders and may help develop sex-specific interventions to treat PTSD.

Beta-hydroxybutyrate, an endogenous NLRP3 inflammasome inhibitor, attenuates anxiety-related behavior in a rodent post-traumatic stress disorder model

Accumulating evidence suggests that elevated inflammation contributes to the pathophysiology of post-traumatic stress disorder (PTSD) and that anti-inflammatory drugs might be a new treatment strategy for PTSD. It has been reported that beta-hydroxybutyrate (BHB), one of the main ketone bodies produced, can have an anti-inflammatory and antidepressant effect. Here, we investigated the potential anti-anxiety and anti-inflammatory effects of BHB using a rodent PTSD model, induced by single prolonged stress (SPS). Male, Sprague–Dawley rats were employed in this study. Repeated administration of BHB attenuated SPS-induced anxiety-related behaviors evaluated by the elevated plus maze test. SPS increased the serum levels of TNF-α and IL-1β. In contrast, BHB administration partially attenuated the increase of serum TNF-α. These findings demonstrate that BHB exerts its anxiolytic effects, possibly by inhibiting systemic TNF-α. Hence, BHB may be a novel therapeutic candidate for the treatment of PTSD.

A Comparison of Hematological, Immunological, and Stress Responses to Capture and Transport in Wild White Rhinoceros Bulls (Ceratotherium simum simum) Supplemented With Azaperone or Midazolam

Capture and transport are essential procedures for the management and conservation of southern white rhinoceroses (Ceratotherium simum simum), but are associated with stress-induced morbidity and mortality. To improve conservation efforts, it is crucial to understand the pathophysiology of rhinoceros stress responses and investigate drug combinations that could reduce these responses. In this study we measured rhinoceros stress responses to capture and transport by quantifying hematological and immunological changes together with adrenal hormone concentrations. We investigated whether the potent anxiolytic drug midazolam was able to mitigate these responses compared to azaperone, which is more commonly used during rhinoceros transport. Twenty three wild white rhinoceros bulls were transported for 6 h (280 km) within the Kruger National Park for reasons unrelated to this study. Rhinoceroses were immobilized with either etorphine-azaperone (group A, n = 11) or etorphine-midazolam (group M, n = 12) intramuscularly by darting from a helicopter. Azaperone (group A) or midazolam (group M) were re-administered intramuscularly every 2 h during transport. Serial blood samples were collected at capture (TC), the start of transport (T0) and after 6 h of transport (T6). Changes in hematological and immunological variables over time and between groups were compared using general mixed models. Increases in plasma epinephrine and serum cortisol concentrations indicated that rhinoceroses mounted a stress response to capture and transport. Packed cell volume decreased from TC to T6 indicating that stress hemoconcentration occurred at TC. Neutrophils progressively increased and lymphocytes and eosinophils progressively decreased from T0 to T6, resulting in an increase in neutrophil to lymphocyte ratio; a characteristic leukocyte response to circulating glucocorticoids. A reduction in serum iron concentrations may suggest the mounting of an acute phase response. Rhinoceroses experienced a decrease in unsaturated fatty acids and an increase in lipid peroxidation products at capture and toward the end of transport indicating oxidative stress. Midazolam, at the dose used in this study, was not able to mitigate adrenal responses to stress and appeared to directly influence leukocyte responses.

Beneficial role of central anticholinergic agent in preventing the development of symptoms in mouse model of post-traumatic stress disorder

Objectives The present study was designed to investigate the effectiveness of trihexyphenidyl, a central anticholinergic drug, in preventing the post-traumatic stress disorder (PTSD) symptoms in a mouse model. Methods Mice were subjected to underwater trauma stress for 30 s on day 1 followed by three situational reminders (3rd, 7th and 14th day). Thereafter, the behavioral alterations including freezing behavior were noted on 21st day. The serum corticosterone levels were measured as a biochemical marker of trauma. Elevated plus maze test was done on day 1 and day 2 to assess the memory formation following exposure to trauma. Results Trauma and situational reminders were associated with a significant development of behavioral changes and freezing behavior on the 21st day. Moreover, there was also a significant decrease in the serum corticosterone levels. A single administration of trihexyphenidyl (2 and 5 mg/kg) significantly restored trauma associated-behavioral changes and serum corticosterone levels. Moreover, it significantly increased the transfer latency time on day 2 following stress exposure in comparison to normal mice suggesting the inhibition of memory formation during trauma exposure. Trihexyphenidyl also led to significant reduction in freezing behavior in response to situational reminders again suggesting the inhibition of formation of aversive fear memory. Conclusion The blockade of central muscarinic receptors may block the formation of aversive memory during the traumatic event, which may be manifested in form of decreased contextual fear response during situational reminders. Central anticholinergic agents may be potentially useful as prophylactic agents in preventing the development of PTSD symptoms.

Environmental enrichment increases cue-dependent freezing and behavioral despair but decreases anxiety-like behavior in rats

While post-traumatic stress disorder (PTSD) can develop after exposure to severe traumatic events, data have shown that individuals with high sensation-seeking personality traits are less prone to developing PTSD. The current study used the rodent environmental enrichment preclinical model of sensation-seeking to determine if similar sensation seeking effects in animal models of PTSD-like behaviors were found. The study also attempted to determine whether environmental enrichment altered the effects of midazolam on these PTSD-like behaviors. Male Sprague-Dawley rats were received at postnatal day (PND) 21 and placed into either an enriched (EC), isolated (IC), or social (SC) condition. Beginning on PND 51, the animals underwent 3 fear conditioning trials where a tone was paired with a 2 s 0.7 mA footshock. Twenty-four hours later, rats were given 15-min i.p. pretreatments of 0, 0.5, or 1.5 mg/kg midazolam, before being placed into fear conditioning chambers for a test of expression of conditioned fear response in a novel context. Following fear conditioning, rodents were also tested in the elevated plus maze (EPM) and the forced swim task (FST) following pretreatments of midazolam. Results from fear conditioning indicated IC rats showed a significant decrease in freezing during acquisition compared to EC and SC rats. Also, during expression, IC rats had lower freezing following saline injections and 0.5 mg/kg midazolam but were equal in time freezing to EC and SC rats following 1.5 mg/kg midazolam. In the EPM there were no effects of midazolam and IC rats showed decreased time spent in the open arms compared to EC and SC rats. In FST, IC rats spent less time immobile and more time swimming compared to EC and SC rats. Overall, results suggest that the rodent environmental enrichment model of sensation-seeking seems to parallel the effects of sensation-seeking on likelihood of PTSD symptoms seen in humans.

Translocator protein 18 kDa: a potential therapeutic biomarker for post traumatic stress disorder

Post traumatic stress disorder (PTSD) is widely regarded as a stress-related and trauma disorder. The symptoms of PTSD are characterized as a spectrum of vulnerabilities after the exposure to an extremely traumatic stressor. Considering as one of complex mental disorders, little progress has been made toward its diagnostic biomarkers, despite the involvement of PTSD has been studied. Many studies into the underlying neurobiology of PTSD implicated the dysfunction of neurosteroids biosynthesis and neuorinflammatory processes. Translocator protein 18 kDa (TSPO) has been considered as one of the promising therapeutic biomarkers for neurological stress disorders (like PTSD, depression, anxiety, et al) without the benzodiazepine-like side effects. This protein participates in the formation of neurosteroids and modulation of neuroinflammation. The review outlines current knowledge involving the role of TSPO in the neuropathology of PTSD and the anti-PTSD-like effects of TSPO ligands.

Antidepressant-Like Effects of Hesperidin in Animal Model of Post-Traumatic Stress Disorder

OBJECTIVE

Post-traumatic stress disorder (PTSD) is a psychiatric disorder characterized by depression and anxiety, that arises due to an imbalance of neurotransmitters in response to excessive stress. Hesperidin (HSD) is a naturally occurring flavonoid shown to exert a variety of biological activities, including antioxidant, anti-inflammatory, and neuroprotective effects.

METHODS

This study was used the open field test (OFT) and forced swimming test (FST) to examine the effects of HSD on the depression-like response of rats after exposure to a single prolonged stress (SPS) leading to the dysregulation of the serotonergic activation system. Male rats were given HSD (20, 50, and 100 mg/kg, intraperitoneal injection, n=6-7 per group) once daily for 14 days after exposure to SPS. The influence of administration of HSD on SPS-induced behavioral responses and concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and monoamine oxidase-A (MAO-A) in the rat brain were also investigated using enzyme-linked immunoassays (ELISAs).

RESULTS

Daily HSD administration signifificantly improved depression-like behaviors in the FST (P0.05), increased the number of lines crossed in the central zone of the OFT (P0.01), and reduced freezing behavior both in contextual and cued fear conditioning. HSD treatment also attenuated the reduction in SPS-induced 5-HT concentrations in the hippocampus and amygdala. This increase in 5-HT concentrations during HSD treatment was partially attributed to a decrease in the 5-HIAA/5-HT ratio in the hippocampus of rats with PTSD. Furthermore, HSD treatment inhibited activity of MAO-A and decreases of tryptophan hydroxylase-1 expression in the hippocampus.

CONCLUSION

HSD was shown to exert antidepressant effects in rats exposed to SPS, suggesting that this natural flflavonoid may be an effective medicine for PTSD.

Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites

The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Variation in the onset of CO2-induced anxiety in female Sprague Dawley rats

Carbon dioxide (CO₂) is commonly used to kill laboratory rats. Rats find CO₂ aversive and aversion varies between individuals, indicating that rats vary in CO₂ sensitivity. Healthy humans experience feelings of anxiety at concentrations similar to those avoided by rats, and these feelings are diminished by the administration of benzodiazepines. Our aim was to assess the effects of the benzodiazepine midazolam on individual thresholds of rat aversion to CO₂. Six female Sprague Dawley rats were repeatedly exposed to CO₂ gradual-fill in approach-avoidance testing. The first three exposures were to a control-treatment followed by three exposures to midazolam (0.375 mg/kg). Within each treatment aversion to CO₂ was not affected by exposure number; however, tolerance increased from an average of 10.7% CO₂ avoided during control sessions, to 15.5% CO₂ avoided when treated with midazolam. These results indicate that rats experience anxiety when exposed to CO₂, and that variation in rat CO₂ sensitivity is driven by individual differences in the onset of these feelings of anxiety. No rat tolerated CO₂ concentrations required to induce loss of consciousness.

The anxiolytic-like effects of ginsenoside Rg2 on an animal model of PTSD

Post traumatic stress disorder (PTSD) is one of the mental illness. The antidepressant-like properties of ginsenoside Rg2 (GRg2) have been shown, while little is known about its anti-PTSD-like effects. In the present study, the PTSD-associated behavioral deficits in rats were induced following exposure to single prolonged stress (SPS). The results showed that the decreased time and entries in the open arms in elevated plus maze test (EPMT) and increased freezing duration in contextual fear paradigm (CFP) were reversed by GRg2 (10 and 20 mg/kg) without affecting the locomotor activity. In addition, GRg2 (10 and 20 mg/kg) could block the decreased levels of progesterone, allopregnanolone, serotonin (5-HT), 5-Hydroxyindoleacetic acid (5-HIAA), corticotropin releasing hormone (CRH), corticosterone (Cort) and adrenocorticotropic hormone (ACTH) in the brain or serum. In summary, GRg2 alleviated the PTSD-associated behavioral deficits with biosynthesis of neurosteroids, normalization of serotonergic system and HPA axis dysfunction.

The anxiolytic-like effects of puerarin on an animal model of PTSD

Post traumatic stress disorder (PTSD) is a mental illness that affected numerous people. The anti-PTSD-like effects of puerarin is unknown, although the antidepressant- and anxiolytic- like effects of puerarin have been reported. The PTSD behavioral deficits in rats were induced by single prolonged stress (SPS), mainly including the reduced time/entries in the open arms and the elevated time/entries in the closed arms in elevated plus maze test, increased freezing duration in contextual fear paradigm and lowered time/entries in the central zone in open field test. However, the behavioral deficits were attenuated by puerarin (50 and 100 mg/kg) without affecting the locomotor activity. For the evaluation of mechanism, the decreased levels of progesterone, allopregnanolone, and the increased levels of corticosterone, corticotropin releasing hormone, and adrenocorticotropic hormone in the brain or serum were induced by SPS, which is blocked by puerarin. In summary, the anti-PTSD-like effects of puerarin were associated with biosynthesis of neurosteroids and normalized levels of stress hormones in HPA axis.

New neurons restore structural and behavioral abnormalities in a rat model of PTSD

Post-traumatic stress disorder (PTSD) has been associated with anxiety, memory impairments, enhanced fear, and hippocampal volume loss, although the relationship between these changes remain unknown. Single-prolonged stress (SPS) is a model for PTSD combining three forms of stress (restraint, swim, and anesthesia) in a single session that results in prolonged behavioral effects. Using pharmacogenetic ablation of adult neurogenesis in rats, we investigated the role of new neurons in the hippocampus in the long-lasting structural and behavioral effects of SPS. Two weeks after SPS, stressed rats displayed increased anxiety-like behavior and decreased preference for objects in novel locations regardless of the presence or absence of new neurons. Chronic stress produced by daily restraint for 2 or 6 hr produced similar behavioral effects that were also independent of ongoing neurogenesis. At a longer recovery time point, 1 month after SPS, rats with intact neurogenesis had normalized, showing control levels of anxiety-like behavior. However, GFAP-TK rats, which lacked new neurons, continued to show elevated anxiety-like behavior and enhanced serum corticosterone response to anxiogenic experience. Volume loss in ventral CA1 region of the hippocampus paralleled increases in anxiety-like behavior, occurring in all rats exposed to SPS at the early time point and only rats lacking adult neurogenesis at the later time point. In chronic stress experiments, volume loss occurred broadly throughout the dentate gyrus and CA1 after 6-hr daily stress but was not apparent in any hippocampal subregion after 2-hr daily stress. No effect of SPS was seen on cell proliferation in the dentate gyrus, but the survival of young neurons born a week after stress was decreased. Together, these data suggest that new neurons are important for recovery of normal behavior and hippocampal structure following a strong acute stress and point to the ventral CA1 region as a potential key mediator of stress-induced anxiety-like behavior.

Animal models of PTSD: a challenge to be met

Recent years have seen increased interest in psychopathologies related to trauma exposure. Specifically, there has been a growing awareness to posttraumatic stress disorder (PTSD) in part due to terrorism, climate change-associated natural disasters, the global refugee crisis, and increased violence in overpopulated urban areas. However, notwithstanding the increased awareness to the disorder, the increasing number of patients, and the devastating impact on the lives of patients and their families, the efficacy of available treatments remains limited and highly unsatisfactory. A major scientific effort is therefore devoted to unravel the neural mechanisms underlying PTSD with the aim of paving the way to developing novel or improved treatment approaches and drugs to treat PTSD. One of the major scientific tools used to gain insight into understanding physiological and neuronal mechanisms underlying diseases and for treatment development is the use of animal models of human diseases. While much progress has been made using these models in understanding mechanisms of conditioned fear and fear memory, the gained knowledge has not yet led to better treatment options for PTSD patients. This poor translational outcome has already led some scientists and pharmaceutical companies, who do not in general hold opinions against animal models, to propose that those models should be abandoned. Here, we critically examine aspects of animal models of PTSD that may have contributed to the relative lack of translatability, including the focus on the exposure to trauma, overlooking individual and sex differences, and the contribution of risk factors. Based on findings from recent years, we propose research-based modifications that we believe are required in order to overcome some of the shortcomings of previous practice. These modifications include the usage of animal models of PTSD which incorporate risk factors and of the behavioral profiling analysis of individuals in a sample. These modifications are aimed to address factors such as individual predisposition and resilience, thus taking into consideration the fact that only a fraction of individuals exposed to trauma develop PTSD. We suggest that with an appropriate shift of practice, animal models are not only a valuable tool to enhance our understanding of fear and memory processes, but could serve as effective platforms for understanding PTSD, for PTSD drug development and drug testing.

The 18 kDa Translocator Protein (TSPO) Overexpression in Hippocampal Dentate Gyrus Elicits Anxiolytic-Like Effects in a Mouse Model of Post-traumatic Stress Disorder

The translocator protein (18 kDa) (TSPO) recently attracted increasing attention in the pathogenesis of post-traumatic stress disorder (PTSD). This study is testing the hypothesis that the overexpression of TSPO in hippocampus dentate gyrus (DG) could alleviate the anxiogenic-like response in the mice model of PTSD induced by foot-shock. In this study, hippocampal DG overexpression of TSPO significantly reversed the increase of the contextual freezing response, the decrease of the percentage of both entries into and time spent in the open arms in elevated plus maze test and the decrease of the account of crossings from the dark to light compartments in light–dark transition test induced by electric foot-shocks procedure. It was further showed that the behavioral effects of TSPO overexpression were blocked by PK11195, a selective TSPO antagonist. In addition, the expression of TSPO and level of allopregnanolone (Allo) decreased in the mouse model of PTSD, which was blocked by overexpression of TSPO in hippocampal dentate gyrus. The difference of neurogenesis among groups was consistent with the changes of TSPO and Allo, as evidenced by bromodeoxyuridine (BrdU)- positive cells in the hippocampal dentate gyrus. These results firstly suggested that TSPO in hippocampal dentate gyrus could exert a great effect on the occurrence and recovery of PTSD in this animal model, and the anti-PTSD-like effect of hippocampal TSPO over-expression could be at least partially mediated by up-regulation of Allo and subsequent stimulation of the adult hippocampal neurogenesis.

Effects of Epigallocatechin Gallate on Behavioral and Cognitive Impairments, Hypothalamic-Pituitary-Adrenal Axis Dysfunction, and Alternations in Hippocampal BDNF Expression Under Single Prolonged Stress

Post-traumatic stress disorder (PTSD) is a traumatic stress-related psychiatric disorder stimulated by experience. Green tea has potent antioxidative properties, due, in part, to the catechin (-) epigallocatechin-3-gallate (EGCG). EGCG is an important polyphenol with advantageous effects on anxiety and depression. Nevertheless, the mechanism about the inhibition of PTSD-like symptoms of EGCG is still unidentified. We examined whether EGCG improved learning and memory deficit stimulated in rats after single prolonged stress (SPS). Rats were administrated intraperitoneally (i.p.) with EGCG for 14 successive days after the SPS process. The SPS procedure stimulated cognitive deficit in the Morris water maze test and the object recognition task, and this impairment was improved by EGCG (25 mg/kg, i.p.). Daily EGCG administration significantly decreased the freezing response to contextual fear conditioning. The administration of EGCG also significantly moderated memory-related decreases in the alternation of cAMP-response element-binding protein and brain-derived neurotrophic factor in the hippocampus. Our results suggest that EGCG alleviated SPS-stimulated learning and memory deficit by inhibiting the increase of neuroinflammation in the rat brain. In addition, EGCG reversed the alternation of allopregnanolone and progesterone in the brain, and diminished simultaneously the hypothalamic-pituitary-adrenal axis dysfunction. Thus, EGCG reversed learning and memory-related behavioral dysfunction and molecular alternation accelerated by traumatic stress and may be a useful therapeutic material for PTSD.

Anxiolytic-like effects of paeoniflorin in an animal model of post traumatic stress disorder

Post-traumatic stress disorder (PTSD) is the serious psychiatric disorder. Paeoniflorin (PF) produces the antidepressant-like properties. However, few studies are concerned about its anti-PTSD-like effects and mechanisms. To investigate these, the single prolonged stress (SPS) model was utilized. PTSD-like behavioral deficits in rats after exposure to SPS were improved by PF (10 and 20 mg/kg, i.p.), evidenced by blocking increased freezing time in contextual fear paradigm (CFP) and increased time and entries in open arms in elevated plus maze (EPM) test without affecting the locomotor activity in open field (OF) test. We also found that increased levels of corticosterone (Cort), corticotropin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) after exposure to SPS were reversed by PF (10 and 20 mg/kg, i.p.) in serum, respectively. Moreover, the decreased levels of serotonin (5-HT) and 5-Hydroxyindoleacetic acid (5-HIAA) in prefrontal cortex and hippocampus were reversed by PF (10 and 20 mg/kg, i.p.), respectively. In summary, the anti-PTSD-like activities of PF were associated with the modulation of HPA axis and 5-HT system activation.

Different effects of dexmedetomidine and midazolam on the expression of NR2B and GABAA-α1 following peripheral nerve injury in rats

Neuropathic pain is a complex, chronic pain condition and the treatment is a major clinical challenge. Recent studies have shown that two FDA approved drugs dexmedetomidine (DEX) and midazolam (MZL), may be useful in treating neuropathic pain, but the mechanism is not fully dementated. Here, we investigated the effects and mechanisms of DEX and MZL treatment in the peripheral nerve injury model. Intramuscular injection with DEX and MZL attenuated the development of mechanical allodynia and thermal hyperalgesia in rats with chronic constriction injury (CCI). Concurrently, the expression of NMDA receptor subunit 2B (NR2B), GABA (A) receptor subunit alpha1 (GABAA-α1), and Sonic Hedgehog (SHH) displayed different temporal patterns in the thalamus and the ipsilateral dorsal horn of the spinal cord after CCI. Such that (1) NR2B expression was decreased on day 1 and 14, whereas GABAA-α1 expression was increased on day 1 in the thalamus, and NR2B expression was decreased on day 1, whereas GABAA-α1 expression was increased on day 1 and day 30 in the ipsilateral spinal cord dorsal horn after DEX treatment. (2) NR2B expression was increased on day 1, then decreased on day 14 and returned to baseline on day30, whereas GABAA-α1 expression was no significant changes on day 1, 14, 30 in the thalamus, and NR2B expression was decreased on day 14 and 30, whereas GABAA-α1 expression was no changes on day 1 and 14 but increased on day 30 after MZL treatment. Furthermore, the mechanical allodynia was significantly attenuated after PUR administration. Meanwhile the expression of NR2B was significantly decreased, and the expression of GABAA-α1 was significantly increased, in the thalamus and in the ipsilateral spinal cord dorsal horn when detected on postoperative day 1, 7, and 14. Our findings indicate that DEX and MZL have different mechanisms in CCI rats, suggesting different strategies could be considered in managing neuropathic pain in different individuals. © 2018 IUBMB Life, 70(2):143-152, 2018.

Single-Prolonged Stress: A Review of Two Decades of Progress in a Rodent Model of Post-traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a common, costly, and often debilitating psychiatric condition. However, the biological mechanisms underlying this disease are still largely unknown or poorly understood. Considerable evidence indicates that PTSD results from dysfunction in highly-conserved brain systems involved in stress, anxiety, fear, and reward. Pre-clinical models of traumatic stress exposure are critical in defining the neurobiological mechanisms of PTSD, which will ultimately aid in the development of new treatments for PTSD. Single prolonged stress (SPS) is a pre-clinical model that displays behavioral, molecular, and physiological alterations that recapitulate many of the same alterations observed in PTSD, illustrating its validity and giving it utility as a model for investigating post-traumatic adaptations and pre-trauma risk and protective factors. In this manuscript, we review the present state of research using the SPS model, with the goals of (1) describing the utility of the SPS model as a tool for investigating post-trauma adaptations, (2) relating findings using the SPS model to findings in patients with PTSD, and (3) indicating research gaps and strategies to address them in order to improve our understanding of the pathophysiology of PTSD.

Effects of GABAa receptor antagonists on motor behavior in pharmacological Parkinson's disease model in mice

The aim of this study was to evaluate the effects of two gamma‐amino butyric acid (GABA)a receptor antagonists on motor behavioral tasks in a pharmacological model of Parkinson disease (PD) in rodents. Ninety‐six Swiss mice received intraperitoneal injection of Haloperidol (1 mg/kg) to block dopaminergic receptors. GABAa receptors antagonists Bicuculline (1 and 5 mg/kg) and Flumazenil (3 and 6 mg/kg) were used for the assessment of the interaction among these neurotransmitters, in this PD model. The motor behavior of the animals was evaluated in the catalepsy test (30, 60, and 90 min after drugs application), through open field test (after 60 min) and trough functional gait assessment (after 60 min). Both Bicuculline and Flumazenil were able to partially reverse catalepsy induced by Haloperidol. In the open field test, Haloperidol reduced the number of horizontal and vertical exploration of the animals, which was not reversed trough application of GABAa antagonists. Furthermore, the functional gait assessment was not sensitive enough to detect motor changes in this animal model of PD. There is an interaction between dopamine and GABA in the basal ganglia and the blocking GABAa receptors may have therapeutic potential in the treatment of PD.

Regulation of Mitochondrial, Cellular, and Organismal Functions by TSPO

In 1999, the enigma of the 18kDa mitochondrial translocator protein (TSPO), also known as the peripheral-type benzodiazepine receptor, was the seeming disparity of the many functions attributed to TSPO, ranging from the potential of TSPO acting as a housekeeping gene at molecular biological levels to adaptations to stress, and even involvement in higher emotional and cognitive functioning, such as anxiety and depression. In the years since then, knowledge regarding the many functions modulated by TSPO has expanded, and understanding has deepened. In addition, new functions could be firmly associated with TSPO, such as regulation of programmed cell death and modulation of gene expression. Interestingly, control by the mitochondrial TSPO over both of these life and death functions appears to include Ca⁺⁺ homeostasis, generation of reactive oxygen species (ROS), and ATP production. Other mitochondrial functions under TSPO control are considered to be steroidogenesis and tetrapyrrole metabolism. As TSPO effects on gene expression and on programmed cell death can be related to the wide range of functions that can be associated with TSPO, several of these five elements of Ca⁺⁺, ROS, ATP, steroids, and tetrapyrroles may indeed form the basis of TSPO's capability to operate as a multifunctional housekeeping gene to maintain homeostasis of the cell and of the whole multicellular organism.

A perspective on the contribution of animal models to the pharmacological treatment of posttraumatic stress disorder

OBJECTIVES

Posttraumatic stress disorder (PTSD) is a prevalent, chronic, disabling disorder that may develop following exposure to a traumatic event. This review summarizes currently used animal models of PTSD and their potential role in the development of better therapeutics. Heterogeneity is one of the main characteristics of PTSD with the consequence that many pharmacological approaches are used to relieve symptoms of PTSD. To address the translational properties of the animal models, we discuss the types of stressors used, the rodent correlates of human PTSD (DSM-5) symptoms, and the efficacy of approved, recommended and off-label drugs used to treat PTSD in 'PTSD-animals'.

CONCLUSIONS

Currently available animal models reproduce most PTSD symptoms and are validated by existing therapeutics. However, novel therapeutics are needed for this disorder as not one drug alleviates all symptoms and many have side effects that lead to non-compliance among PTSD patients. The true translational power of animal models of PTSD will only be demonstrated when new therapeutics acting through novel mechanisms become available for clinical practice.

Overexpression of the 18 kDa translocator protein (TSPO) in the hippocampal dentate gyrus produced anxiolytic and antidepressant-like behavioural effects

The 18 kDa translocator protein (TSPO) is a five transmembrane domain protein that plays a crucial role in neurosteroid (e.g., allopregnanolone) synthesis by promoting the transport of cholesterol to the inner mitochondrial membrane. This protein is predominantly expressed in steroid-synthesizing tissues, including the central and peripheral nervous system, affecting stress-related disorders such as anxiety and depression. Recent studies have focused on the hippocampal dentate gyrus, which is very important for involvement of anxiety and depression. However, the exact role that TSPO plays in the pathophysiology of anxiety and depression and the involvement of the hippocampal dentate gyrus in regulating these behavioural effects remain elusive. This study used the lentiviral vectors mediating TPSO overexpression to assess the effects of TPSO overexpression in the hippocampal dentate gyrus on anxiolytic and antidepressant-like behavioural effects in mice. The expression of TSPO and the concentration of allopregnanolone in hippocampus tissues (3 mm in diameter around the injection site on both sides) were measured by Western blot and ELISA, respectively. The results indicated that microinjection of the LV-TSPO resulted in a significant increase in TSPO expression and allopregnanolone concentration in the hippocampus. Moreover, TSPO overexpression of the mouse hippocampal dentate gyrus generated significant anxiolytic and antidepressant-like behavioural effects in a series of behavioural models. These effects were completely blocked by the TSPO antagonist PK11195 (3 mg/kg, intraperitoneally) and the 5α-reductase inhibitor finasteride (5 mg/kg,intraperitoneally). Meanwhile, the increased allopregnanolone was also reversed by PK11195 and finasteride. In addition, neither PK11195 nor finasteride had an effect on the expression of TSPO. Overall, our results are the first to suggest that the overexpression of TSPO in the hippocampal dentate gyrus produced anxiolytic and antidepressant-like behavioural effects that are partially mediated by downstream allopregnanolone biosynthesis. Our results suggest that TSPO would be a potential anxiolytic and antidepressant therapeutic target.

Anti-PTSD-like effects of albiflorin extracted from Radix paeoniae Alba

ETHNOPHARMACOLOGY RELEVANCE

Post-traumatic stress disorder (PTSD) is a severe psychiatric disorder that is characterized by symptoms of re-experiencing, avoidance and hyperarousal, as well as social and professional dysfunction at least one month after the exposure to a traumatic event. Biosynthesis of allopregnanolone has been suggested as one of the important contributors to PTSD. Albiflorin (AF) extracted from Radix paeoniae Alba had been shown to be effective in the therapy of depression. However, few studies were concerned about the anti-PTSD-like effects of AF.

AIM OF THE STUDY

The current study aimed to evaluate the anti-PTSD-like effects of AF in an animal model and its possible mechanism.

MATERIALS AND METHODS

To evaluate this, the single prolonged stress (SPS) model was used in the present study. The SPS rats were administered by AF (at doses of 3.5, 7 and 14.0mg/kg, i.g.) after induction of SPS from days 2-13. After the exposure to SPS, behavioral assessments were conducted, including contextual fear paradigm (CFP), elevated plus-maze test (EPMT), open-field test (OFT). The rats were decapitated at the end of the behavioral tests and levels of allopregnanolone in prefrontal cortex, hippocampus and amygdala were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

It had been shown that behavioral deficits of SPS rats were reversed by AF (7.0 and 14.0mg/kg, i.g.), which attenuated the PTSD-like associated contextual freezing behavior in CFP and improved PTSD-like associated anxiogenic behavior in EPMT without affecting locomotor activity in OFT. Moreover, decreased levels of allopregnanolone in prefrontal cortex, hippocampus, and amygdala were reversed by AF (7.0 and 14.0mg/kg, i.g.), respectively.

CONCLUSION

In summary, the present study indicated that AF exerted the anti-PTSD-like effects, which maybe associated with allopregnanolone biosynthesis in the brain.

The antidepressant-like activity of AC-5216, a ligand for 18KDa translocator protein (TSPO), in an animal model of diabetes mellitus

Diabetes mellitus is a chronic disease that is associated with depression. Also, depression is common in adults with type 2 diabetes mellitus (T2DM). Translocator protein (18kDa) (TSPO) and allopregnanolone play an important role in the depression treatment. However, few studies have evaluated TSPO and allopregnanolone in the treatment of depression in T2DM. AC-5216, a ligand for TSPO, produces anxiolytic- and antidepressant-like effects in animal models. The present study aimed to explore antidepressant-like effects of AC-5216 on diabetic rats. Following the development of diabetic model induced by high fat diet (HFD) feeding and streptozotocin (STZ), AC-5216 (0.3 and 1 mg/kg, i.g.) elicited the antidepressant-like effects in behavioral tests while these activities were blocked by TSPO antagonist PK11195 (3 mg/kg, i.p.). The levels of allopregnanolone in the prefrontal cortex and hippocampus were increased by AC-5216 (0.3 and 1 mg/kg, i.g.), which was antagonized by PK11195 (3 mg/kg, i.p.). The increased plasma glucose (PG) and decreased insulin (INS) in HFD-STZ rats were reversed by AC-5216 (0.3 and 1 mg/kg, i.g.). This study indicates that the antidepressant-like effects of AC-5216 on HFD-STZ rats, suggesting that TSPO may represent a novel therapeutic target for depression in T2DM.

Midazolam and ropivacaine act synergistically to inhibit bone cancer pain with different mechanisms in rats

Analgesic strategy of a single drug analgesia in bone cancer pain (BCP) has shifted to combined analgesia with different drugs which have different mechanism. After tumor cell inculation, the activation of signal transducer and activator of transcription (STAT3) and extracellular signal-regulated kinase (ERK) signaling pathway are involved in the development and maintenance of BCP, whereas a decrease in the expression of spinal STAT3 and ERK through using their specific blocker, lead to attenuation of BCP. Hence, in this study, we clarified that intrathecal (i.t.) injection of midazolam (MZL) and ropivacaine (Ropi) induces synergistic analgesia on BCP and is accompanied with different mechanisms of these analgesic effect. Hargreaves heat test was used to detect the analgesic effect of single dose of i.t. MZL, Ropi and their combination on the BCP rats. At consecutive daily administration experiment, thermal hyperalgesia was recorded, and immunohistochemical staining was used to detect the expression of c-Fos, spinal glial fibrillary acidic protein (GFAP) and ionized calcium binding adapter molecule-1 (IBA-1). Then, western blot analysis was used to examine spinal TSPO, GFAP, IBA-1, pERK/ERK and pSTAT3/STAT3 levels on day 14 after tumor cell inoculation. i.t. MZL or Ropi showed a short-term analgesia dose-dependently, and MZL displayed better effect on inhibition of pSTAT3 expression than pERK, but Ropi was just the reverse, then consecutive daily administrations of their combination acted synergistically to attenuate thermal hyperalgesia with downregulated spinal 'neuron-astrocytic activation' in the BCP rats. i.t. co-delivery of MZL and Ropi shows synergistic analgesia on the BCP with the inhibition of spinal 'neuron-astrocytic activation'. Spinal different signaling pathway inhibition for MZL and Ropi may be involved in this process.

The inulin-type oligosaccharides extract from morinda officinalis, a traditional Chinese herb, ameliorated behavioral deficits in an animal model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a severe psychiatric condition. The allopregnanolone biosynthesis has been implicated as one of the possible contributors to PTSD. Inulin-type oligosaccharides of morinda officinalis (IOMO) had been shown to be effective in the therapy of depression. However, few studies concern the anti-PTSD-like effects of IOMO. To evaluate this, the single prolonged stress (SPS) model was used in the present study. It had been shown that the behavioral deficits of SPS-treated rats were reversed by IOMO (25.0 and 50.0 mg/kg, i.p.), which reversed the increased freezing time in contextual fear paradigm (CFP) and the decreased time and entries in open arms in the elevated plus maze (EPM) test without affecting the locomotor activity in the open field (OF) test. In addition, the decreased allopregnanolone in the prefrontal cortex, hippocampus, and amygdala was reversed by IOMO (25.0 and 50.0 mg/kg, i.p.), respectively. In summary, the present study indicated that the IOMO exert anti-PTSD-like behaviors, which maybe associated with the brain allopregnanolone biosynthesis.

TSPO: kaleidoscopic 18-kDa amid biochemical pharmacology, control and targeting of mitochondria

The 18-kDa translocator protein (TSPO) localizes in the outer mitochondrial membrane (OMM) of cells and is readily up-regulated under various pathological conditions such as cancer, inflammation, mechanical lesions and neurological diseases. Able to bind with high affinity synthetic and endogenous ligands, its core biochemical function resides in the translocation of cholesterol into the mitochondria influencing the subsequent steps of (neuro-)steroid synthesis and systemic endocrine regulation. Over the years, however, TSPO has also been linked to core cellular processes such as apoptosis and autophagy. It interacts and forms complexes with other mitochondrial proteins such as the voltage-dependent anion channel (VDAC) via which signalling and regulatory transduction of these core cellular events may be influenced. Despite nearly 40 years of study, the precise functional role of TSPO beyond cholesterol trafficking remains elusive even though the recent breakthroughs on its high-resolution crystal structure and contribution to quality-control signalling of mitochondria. All this along with a captivating pharmacological profile provides novel opportunities to investigate and understand the significance of this highly conserved protein as well as contribute the development of specific therapeutics as presented and discussed in the present review.

Acute Stress Decreases but Chronic Stress Increases Myocardial Sensitivity to Ischemic Injury in Rodents

Cardiovascular disease (CVD) is the largest cause of mortality worldwide, and stress is a significant contributor to the development of CVD. The relationship between acute and chronic stress and CVD is well evidenced. Acute stress can lead to arrhythmias and ischemic injury. However, recent evidence in rodent models suggests that acute stress can decrease sensitivity to myocardial ischemia-reperfusion injury (IRI). Conversely, chronic stress is arrhythmogenic and increases sensitivity to myocardial IRI. Few studies have examined the impact of validated animal models of stress-related psychological disorders on the ischemic heart. This review examines the work that has been completed using rat models to study the effects of stress on myocardial sensitivity to ischemic injury. Utilization of animal models of stress-related psychological disorders is critical in the prevention and treatment of cardiovascular disorders in patients experiencing stress-related psychiatric conditions.

Translocator protein mediates the anxiolytic and antidepressant effects of midazolam

The translocator protein (18 kDa) (TSPO) plays an important role in stress-related disorders, such as anxiety, depression and post-traumatic stress disorder (PTSD), caused by neurosteroids (e.g. allopregnanolone). The present study sought to evaluate the significance of TSPO in anxiolytic and antidepressant effects induced by midazolam. The animals were administrated midazolam (0.25, 0.5 and 1 mg/kg, i.p.) and subjected to behavioral tests, including Vogel-type conflict test, elevated plus-maze test, forced swimming test. Midazolam produced anxiolytic- and antidepressant-like effects Vogel-type conflict test (1 mg/kg, i.p.), elevated plus-maze test (0.5 and 1 mg/kg, i.p.), and forced swimming test (0.5 and 1 mg/kg, i.p.). These effects of Midazolam were totally blocked by the TSPO antagonist PK11195 (3 mg/kg, i.p.). To evaluate the role of allopregnanolone in the anxiolytic- and antidepressant-like effects of midazolam, the animals were decapitated at the end of the behavioral tests. The allopregnanolone levels of the prefrontal cortex and hippocampus were measured by enzyme-linked immunosorbent assay (ELISA). The allopregnanolone level of the prefrontal cortex and hippocampus was increased by midazolam (0.5, 1 mg/kg, i.p.) and the increase was reversed by PK11195 (3 mg/kg, i.p.). Overall, the results indicated that the anxiolytic- and antidepressant-like effects of midazolam were mediated by TSPO, via stimulation of allopregnanolone biosynthesis.

Neuroactive steroids and the peripheral nervous system: An update

In the present review we summarize observations to date supporting the concept that neuroactive steroids are synthesized in the peripheral nervous system, regulate the physiology of peripheral nerves and exert notable neuroprotective actions. Indeed, neuroactive steroids have been recently proposed as therapies for different types of peripheral neuropathy, like for instance those occurring during aging, chemotherapy, physical injury and diabetes. Moreover, pharmacological tools able to increase the synthesis of neuroactive steroids might represent new interesting therapeutic strategy to be applied in case of peripheral neuropathy.