Chronic adolescent stress alters GR-FKBP5 interactions in the hippocampus of adult female rats.

Chronic stress exposure during development can have lasting behavioral consequences that differ in males and females. More specifically, increased depressive behaviors in females, but not males, are observed in both humans and rodent models of chronic stress. Despite these known stress-induced outcomes, the molecular consequences of chronic adolescent stress in the adult brain are less clear. The stress hormone corticosterone activates the glucocorticoid receptor, and activity of the receptor is regulated through interactions with co-chaperones-such as the immunophilin FK506 binding proteins 5 (FKBP5). Previously, it has been reported that the adult stress response is modified by a history of chronic stress; therefore, the current study assessed the impact of chronic adolescent stress on the interactions of the glucocorticoid receptor (GR) with its regulatory co-chaperone FKBP5 in response to acute stress in adulthood. Although protein presence for FKBP5 did not differ by group, assessment of GR-FKBP5 interactions demonstrated that adult females with a history of chronic adolescent stress had elevated GR-FKBP5 interactions in the hippocampus following an acute stress challenge which could potentially contribute to a reduced translocation pattern given previous literature describing the impact of FKBP5 on GR activity. Interestingly, the altered co-chaperone interactions of the GR in the stressed female hippocampus were not coupled to an observable difference in transcription of GR-regulated genes. Together, these studies show that chronic adolescent stress causes lasting changes to co-chaperone interactions with the glucocorticoid receptor following stress exposure in adulthood and highlight the potential role that FKBP5 plays in these modifications. Understanding the long-term implications of adolescent stress exposure will provide a mechanistic framework to guide the development of interventions for adult disorders related to early life stress exposures.

Kinetics of Intermediate Release Enhances P450 11B2-Catalyzed Aldosterone Synthesis.

The mitochondrial enzyme cytochrome P450 11B2 (aldosterone synthase) catalyzes the 3 terminal transformations in the biosynthesis of aldosterone from 11-deoxycorticosterone (DOC): 11ß-hydroxylation to corticosterone, 18-hydroxylation, and 18-oxidation. Prior studies have shown that P450 11B2 produces more aldosterone from DOC than from the intermediate corticosterone and that the reaction sequence is processive, with intermediates remaining bound to the active site between oxygenation reactions. In contrast, P450 11B1 (11ß-hydroxylase), which catalyzes the terminal step in cortisol biosynthesis, shares a 93% amino acid sequence identity with P450 11B2, converts DOC to corticosterone, but cannot synthesize aldosterone from DOC. The biochemical and biophysical properties of P450 11B2, which enable its unique 18-oxygenation activity and processivity, yet are not also represented in P450 11B1, remain unknown. To understand the mechanism of aldosterone biosynthesis, we introduced point mutations at residue 320, which partially exchange the activities of P450 11B1 and P450 11B2 (V320A and A320V, respectively). We then investigated NADPH coupling efficiencies, binding kinetics and affinities, and product formation of purified P450 11B1 and P450 11B2, wild-type, and residue 320 mutations in phospholipid vesicles and nanodiscs. Coupling efficiencies for the 18-hydroxylase reaction with corticosterone as the substrate failed to correlate with aldosterone synthesis, ruling out uncoupling as a relevant mechanism. Conversely, corticosterone dissociation rates correlated inversely with aldosterone production. We conclude that intermediate dissociation kinetics, not coupling efficiency, enable P450 11B2 to synthesize aldosterone via a processive mechanism. Our kinetic data also suggest that the binding of DOC to P450 11B enzymes occurs in at least two distinct steps, favoring an induced-fit mechanism.

Sleep rebound leads to marked recovery of prolonged sleep deprivation-induced adversities in the stress response and hippocampal neuroplasticity of male rats.

BACKGROUND: Sleep disturbances are not only frequent symptoms, but also risk factors for major depressive disorder. We previously reported that depressed patients who experienced "Hypersomnia" showed a higher and more rapid response rate under paroxetine treatment, but the underlying mechanism remains unclear. The present study was conducted to clarify the beneficial effects of sleep rebound through an experimental "Hypersomnia" rat model on glucocorticoid and hippocampal neuroplasticity associated with antidepressive potency. METHODS: Thirty-four male Sprague-Dawley rats were subjected to sham treatment, 72-h sleep deprivation, or sleep deprivation and subsequent follow-up for one week. Approximately half of the animals were sacrificed to evaluate adrenal weight, plasma corticosterone level, hippocampal content of mRNA isoforms, and protein of the brain-derived neurotrophic factor (Bdnf) gene. In the other half of the rats, Ki-67- and doublecortin (DCX)-positive cells in the hippocampus were counted via immunostaining to quantify adult neurogenesis. RESULTS: Prolonged sleep deprivation led to adrenal hypertrophy and an increase in the plasma corticosterone level, which had returned to normal after one week follow-up. Of note, sleep deprivation-induced decreases in hippocampal Bdnf transcripts containing exons II, IV, VI, and IX and BDNF protein levels, Ki-67-(+)-proliferating cells, and DCX-(+)-newly-born neurons were not merely reversed, but overshot their normal levels with sleep rebound. LIMITATIONS: The present study did not record electroencephalogram or assess behavioral changes of the sleep-deprived rats. CONCLUSIONS: The present study demonstrated that prolonged sleep deprivation-induced adversities are reversed or recovered by sleep rebound, which supports "Hypersomnia" in depressed patients as having a beneficial pharmacological effect.

Class I histone deacetylases inhibition reverses memory impairment induced by acute stress in mice.

While chronic stress induces learning and memory impairments, acute stress may facilitate or prevent memory consolidation depending on whether it occurs during the learning event or before it, respectively. On the other hand, it has been shown that histone acetylation regulates long-term memory formation. This study aimed to evaluate the effect of two inhibitors of class I histone deacetylases (HDACs), 4-phenylbutyrate (PB) and IN14 (100 mg/kg/day, ip for 2 days), on memory performance in mice exposed to a single 15-min forced swimming stress session. Plasma corticosterone levels were determined 30 minutes after acute swim stress in one group of mice. In another experimental series, independent groups of mice were trained in one of three different memory tasks: Object recognition test, Elevated T maze, and Buried food location test. Subsequently, the hippocampi were removed to perform ELISA assays for histone deacetylase 2 (HDAC2) expression. Acute stress induced an increase in plasma corticosterone levels, as well as hippocampal HDAC2 content, along with an impaired performance in memory tests. Moreover, PB and IN14 treatment prevented memory loss in stressed mice. These findings suggest that HDAC2 is involved in acute stress-induced cognitive impairment. None of the drugs improved memory in non-stressed animals, indicating that HDACs inhibitors are not cognitive boosters, but rather potentially useful drugs for mitigating memory deficits.

Association between social dominance hierarchy and PACAP expression in the extended amygdala, corticosterone, and behavior in C57BL/6 male mice.

The natural alignment of animals into social dominance hierarchies produces adaptive, and potentially maladaptive, changes in the brain that influence health and behavior. Aggressive and submissive behaviors assumed by animals through dominance interactions engage stress-dependent neural and hormonal systems that have been shown to correspond with social rank. Here, we examined the association between social dominance hierarchy status established within cages of group-housed mice and the expression of the stress peptide PACAP in the bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA). We also examined the relationship between social dominance rank and blood corticosterone (CORT) levels, body weight, motor coordination (rotorod) and acoustic startle. Male C57BL/6 mice were ranked as either Dominant, Submissive, or Intermediate based on counts of aggressive/submissive encounters assessed at 12 weeks-old following a change in homecage conditions. PACAP expression was significantly higher in the BNST, but not the CeA, of Submissive mice compared to the other groups. CORT levels were lowest in Submissive mice and appeared to reflect a blunted response following events where dominance status is recapitulated. Together, these data reveal changes in specific neural/neuroendocrine systems that are predominant in animals of lowest social dominance rank, and implicate PACAP in brain adaptations that occur through the development of social dominance hierarchies.

[Restraint stress induces blood-brain barrier injury in rat amygdala by activating the Rho/ROCK signaling pathway].

OBJECTIVE: To investigate the role of Rho/ROCK signaling pathway in mediating restraint stress-induced blood-brain barrier (BBB) injury in the amygdala of rats. METHODS: Sixty male SD rats were randomized equally into control group (with food and water deprivation for 6 h per day), restraint stress group (with restraint for 6 h per day), stress + fasudil treatment (administered by intraperitoneal injection at 1 mg/100 g 30 min before the 6-h restraint) group, and fasudil treatment alone group. The elevated plus-maze test was used to detect behavioral changes of the rats, serum corticosterone and S100B levels were determined with ELISA, and Evans Blue leakage in the brain tissue was examined to evaluate the changes in BBB permeability. The changes in expression levels of tight junction proteins in the amygdala were detected using immunofluorescence assay and Western blotting, and Rho/ROCK pathway activation was detected by Pull-down test and Western blotting. Ultrastructural changes of the cerebral microvascular endothelial cells were observed using transmission electron microscopy. RESULTS: Compared with those in the control group, the rats in restrain stress group and stress+fasudil group showed obvious anxiety-like behavior with significantly increased serum corticosterone level (P<0.001). Compared with those in the control group and stress+fasudil group, the rat models of restrain stress showed more obvious Evans Blue leakage and higher S100B expression (P<0.01) but lower expressions of tight junction proteins in the amygdala. Pull-down test and Western blotting confirmed that the expression levels of RhoA-GTP, ROCK2 and P-MLC 2 were significantly higher in stress group than in the control group and stress + fasudil group (P<0.05). Transmission electron microscopy revealed obvious ultrastructural changes in the cerebral microvascular endothelial cells in the rat models of restrain stress. CONCLUSION: Restraint stress induces BBB injury in the amygdala of rats by activating the Rho/ROCK signaling pathway.

[Saikosaponin a alleviates pentylenetetrazol-induced acute epileptic seizures in mouse models of depression by suppressing microglia activation-mediated inflammation].

OBJECTIVE: To explore the inhibitory effect of saikosonin a (SSa) on pentylenetetrazol-induced acute epilepsy seizures in a mouse model of depression and explore the mechanism mediating this effect. METHODS: Male C57BL/6J mouse models of depression was established by oral administration of corticosterone via drinking water for 3 weeks, and acute epileptic seizures were induced by intraperitoneal injection of a single dose of pentylenetetrazole. The effect of intraperitoneal injection of SSa prior to the treatment on depressive symptoms and epileptic seizures were assessed using behavioral tests, epileptic seizure grading and hippocampal morphology observation. ELISA was used to detect blood corticosterone levels of the mice, and RTqPCR was performed to detect the pro- and anti-inflammatory factors. Microglia activation in the mice was observed using immunofluorescence staining. RESULTS: The mouse model of corticosterone-induced depression showed body weight loss and obvious depressive behaviors with significantly increased serum corticosterone level (all P < 0.05). Compared with those with pentylenetetrazole-induced epilepsy alone, the epileptic mice with comorbid depression showed significantly shorter latency of epileptic seizures, increased number, grade and duration of of seizures, reduced Nissl bodies in hippocampal CA1 and CA3 neurons, increased number of Iba1-positive cells, and significantly enhanced hippocampal expressions of IL-1ß, IL-10, TNF-α and IFN-γ. Pretreatment of the epileptic mice with SSa significantly prolonged the latency of epileptic seizures, reduced the number, duration, and severity of seizures, increased the number of Nissl bodies, decreased the number of Iba1-positive cells, and reduced the expression levels of IL-1ß, IL-10, TNF-α, and IFN-γ in the hippocampus (P < 0.05). CONCLUSION: Depressive state aggravates epileptic seizures, increases microglia activation, and elevates inflammation levels. SSA treatment can alleviate acute epileptic seizures in mouse models of depression possibly by suppressing microglia activation-mediated inflammation.

Puberty Blocker, Leuprolide, Reduces Sex Differences in Rough-and-Tumble Play and Anxiety-like Behavior in Juvenile Rats.

We examined the effect of the puberty blocker, leuprolide acetate, on sex differences in juvenile rough-and-tumble play behavior and anxiety-like behavior in adolescent male and female rats. We also evaluated leuprolide treatment on gonadal and pituitary hormone levels and activity-regulated cytoskeleton-protein messenger RNA levels within the adolescent amygdala, a region important both for rough-and-tumble play and anxiety-like behavior. Our findings suggest that leuprolide treatment lowered anxiety-like behavior during adolescent development, suggesting that the maturation of gonadotropin-releasing hormone systems may be linked to increased anxiety. These data provide a potential new model to understand the emergence of increased anxiety triggered around puberty. Leuprolide also reduced masculinized levels of rough-and-tumble play behavior, lowered follicle-stimulating hormone, and produced a consistent pattern of reducing or halting sex differences of hormone levels, including testosterone, growth hormone, thyrotropin, and corticosterone levels. Therefore, leuprolide treatment not only pauses sexual development of peripheral tissues, but also reduces sex differences in hormones, brain, and behavior, allowing for better harmonization of these systems following gender-affirming hormone treatment. These data contribute to the intended use of puberty blockers in stopping sex differences from developing further with the potential benefit of lowering anxiety-like behavior.

Melatonin alleviates chronic stress-induced hippocampal microglia pyroptosis and subsequent depression-like behaviors by inhibiting Cathepsin B/NLRP3 signaling pathway in rats.

Melatonin improves chronic stress-induced hippocampal damage and depression-like behaviors, but the mechanism needs further study. This study was to explore the mechanism of melatonin inhibiting microglia pyroptosis. In virtro experiments, melatonin improved corticosterone-induced the ultrastructure and microstructure damage of HAPI cells by inhibiting pyroptosis, thereby increasing cell survival rate. Protein-protein interaction network and molecular autodocking predicted that Cathespin B might be the target of melatonin inhibition of NLRP3-mediated pyroptosis. Melatonin inhibited corticosterone-induced Cathespin B expression. Both Cathepsin B inhibitor CA-074Me and NLRP3 knockout inhibited the HAPI cells pyroptosis. Similarly, melatonin inhibited Cathepsin B agonist Pazopanib-induced activation of Cathepsin B/NLRP3 signaling pathway and HAPI cells pyroptosis. In vivo studies, melatonin inhibited chronic restraint stress (CRS)-induced activation of Cathepsin B/NLRP3 signaling pathway and alleviated hippocampal microglia pyroptosis in rats. Inhibition of microglia pyroptosis improved CRS-induced depression-like behaviors of rats. In addition, inhibition of Cathepsin B and NLRP3 alleviated hippocampal pyroptosis. Melatonin inhibited Pazopanib-induced activation of Cathepsin B/NLRP3 signaling pathway and hippocampal pyroptosis. These results demonstrated that melatonin could alleviate CRS-induced hippocampal microglia pyroptosis by inhibiting Cathepsin B/NLRP3 signaling pathway, thereby improving depression-like behaviors in rats. This study reveals the molecular mechanism of melatonin in the prevention and treatment of chronic stress-related encephalopathy.

Mice lacking DIO3 exhibit sex-specific alterations in circadian patterns of corticosterone and gene expression in metabolic tissues.

Disruption of circadian rhythms is associated with neurological, endocrine and metabolic pathologies. We have recently shown that mice lacking functional type 3 deiodinase (DIO3), the enzyme that clears thyroid hormones, exhibit a phase shift in locomotor activity, suggesting altered circadian rhythm. To better understand the physiological and molecular basis of this phenotype, we used Dio3+/+ and Dio3-/- mice of both sexes at different zeitgeber times (ZTs) and analyzed corticosterone and thyroxine (T4) levels, hypothalamic, hepatic, and adipose tissue expression of clock genes, as well as genes involved in the thyroid hormone action or physiology of liver and adipose tissues. Wild type mice exhibited sexually dimorphic circadian patterns of genes controlling thyroid hormone action, including Dio3. Dio3-/- mice exhibited altered hypothalamic expression of several clock genes at ZT12, but did not disrupt the overall circadian profile. Expression of clock genes in peripheral tissues was not disrupted by Dio3 deficiency. However, Dio3 loss in liver and adipose tissues disrupted circadian profiles of genes that determine tissue thyroid hormone action and physiology. We also observed circadian-specific changes in serum T4 and corticosterone as a result of DIO3 deficiency. The circadian alterations manifested sexual dimorphism. Most notable, the time curve of serum corticosterone was flattened in Dio3-/- females. We conclude that Dio3 exhibits circadian variations, influencing the circadian rhythmicity of thyroid hormone action and physiology in liver and adipose tissues in a sex-specific manner. Circadian disruptions in tissue physiology may then contribute to the metabolic phenotypes of DIO3-deficient mice.

Corticosterone Impairs Hippocampal Neurogenesis and Behaviors through p21-Mediated ROS Accumulation.

Stress is known to induce a reduction in adult hippocampal neurogenesis (AHN) and anxiety-like behaviors. Glucocorticoids (GCs) are secreted in response to stress, and the hippocampus possesses the greatest levels of GC receptors, highlighting the potential of GCs in mediating stress-induced hippocampal alterations and behavior deficits. Herein, RNA-sequencing (RNA-seq) analysis of the hippocampus following corticosterone (CORT) exposure revealed the central regulatory role of the p21 (Cdkna1a) gene, which exhibited interactions with oxidative stress-related differentially expressed genes (DEGs), suggesting a potential link between p21 and oxidative stress-related pathways. Remarkably, p21-overexpression in the hippocampal dentate gyrus partially recapitulated CORT-induced phenotypes, including reactive oxygen species (ROS) accumulation, diminished AHN, dendritic atrophy, and the onset of anxiety-like behaviors. Significantly, inhibiting ROS exhibited a partial rescue of anxiety-like behaviors and hippocampal alterations induced by p21-overexpression, as well as those induced by CORT, underscoring the therapeutic potential of targeting ROS or p21 in the hippocampus as a promising avenue for mitigating anxiety disorders provoked by chronic stress.

Prenatal treatment with corticosterone via maternal injection induces learning and memory impairments via delaying postsynaptic development in hippocampal CA1 neurons of rats.

Previously, we reported that prenatal exposure to high corticosterone induced attention-deficit hyperactivity disorder (ADHD)-like behaviors with cognitive deficits after weaning. In the present study, cellular mechanisms underlying cortisol-induced cognitive dysfunction were investigated using rat pups (Corti.Pups) born from rat mothers that were repetitively injected with corticosterone during pregnancy. In results, Corti.Pups exhibited the failure of behavioral memory formation in the Morris water maze (MWM) test and the incomplete long-term potentiation (LTP) of hippocampal CA1 neurons. Additionally, glutamatergic excitatory postsynaptic currents (EPSCs) were remarkably suppressed in Corti.Pups compared to normal rat pups. Incomplete LTP and weaker EPSCs in Corti.Pups were attributed to the delayed postsynaptic development of CA1 neurons, showing a higher expression of NR2B subunits and lower expression of PSD-95 and BDNF. These results indicated that the prenatal treatment with corticosterone to elevate cortisol level might potently downregulate the BDNF-mediated signaling critical for the synaptic development of hippocampal CA1 neurons during brain development, and subsequently, induce learning and memory impairment. Our findings suggest a possibility that the prenatal dysregulation of cortisol triggers the epigenetic pathogenesis of neurodevelopmental psychiatric disorders, such as ADHD and autism.

The impact of prenatal alcohol, synthetic cannabinoid and co-exposure on behavioral adaptations in adolescent offspring and alcohol self-administration in adulthood.

Prenatal exposure to alcohol or cannabinoids can produce enduring neurobiological, cognitive, and behavioral changes in the offspring. Furthermore, prenatal co-exposure to alcohol and cannabinoids induces malformations in brain regions associated with reward and stress-related circuitry. This study examined the effects of co-exposure to alcohol and the synthetic cannabinoid (SCB) CP55,940 throughout gastrulation and neurulation in rats on basal corticosterone levels and a battery of behavioral tests during adolescence and alcohol self-administration in adulthood. Importantly, we find that prenatal alcohol exposure (PAE) caused lower baseline corticosterone levels in adolescent males and females. Co-exposure to alcohol + CP produced hyperactivity during open field test in males, but not females. During the two-bottle choice alcohol-drinking procedure, prenatal cannabinoid exposed male and female adolescent rats drank more alcohol than their vehicle-exposed controls. In adulthood, female rats treated with prenatal cannabinoid exposure (PCE), showed an overall total increase in alcohol intake during alcohol self-administration; but this was not found in males. When the reinforcer was changed to a 1% sucrose solution, male rats exposed to PCE, showed a reduced self-administration compared to vehicle-exposed males, potentially indicative of an anhedonic response. This lower self-administration persisted when 20% alcohol was reintroduced to the sucrose solution. Lastly, following an abstinence period, there were no changes due to prenatal drug exposure in either males or females. Overall, these data suggest lasting consequences of prenatal alcohol and cannabinoid exposure during adolescence and adulthood in male and female rats.

Amelioration by Withania somnifera of neurobehavioural and immunological markers in time dependent sensitization induced post traumatic stress disorder in rats.

AIMS AND OBJECTIVES: Posttraumatic stress disorder (PTSD) is a complex neuropsychiatric pathophysiology with an unmet need for safe, effective, and sustainable therapeutic modalities. Thus, the present study evaluated the effects of Withaniasomnifera (WS, Ashwagandha) on an experimental model of PTSD in rats. MATERIALS AND METHODS: Wistar rats (200-250 g) were used and time-dependent sensitization (TDS) was used as the experimental model of PTSD. Standardized WS root extract (100 and 300 mg/kg, p.o. for 15 days) was administered with TDS and their effects were observed on neurobehavioral (anxiety) and brain cytokines, corticosterone, and oxidative stress markers. RESULTS: Exposure to TDS resulted in anxiogenic behavior in the elevated plus maze (EPM) test, i.e., reductions in open arm entries and open arm time, as compared to the control group. Pretreatment with WS extract (100 and 300 mg/kg × 14 days) attenuated the TDS-induced anxiogenic activity in a dose-related manner, and these WS effects were comparable to those seen after the comparator drug fluoxetine (10 mg/kg). Assay of brain homogenates showed that TDS also resulted in elevations in brain interleukin-6 and reduction in corticosterone levels in both the hippocampus and prefrontal cortex (PFC), which were reversed after WS pretreatments. Further, WS pretreatment also reversed the TDS-induced changes in brain oxidative stress markers, namely elevated malondialdehyde and reduced glutathione levels in both the hippocampus and PFC. CONCLUSION: These results suggest that WS could have potential as a therapeutic agent for treating PTSD by attenuating anxiogenesis, neuroimmune axis activation, and oxidative stress.

Protective effect of hygrolansamycin C against corticosterone-induced toxicity and oxidative stress-mediated via autophagy and the MAPK signaling pathway.

BACKGROUND: Excessive stress, a major problem in modern societies, affects people of all ages worldwide. Corticosterone is one of the most abundant hormones secreted during stressful conditions and is associated with various dysfunctions in the body. In particular, we aimed to investigate the protective effects of hygrolansamycin C (HYGC) against corticosterone-induced cellular stress, a manifestation of excessive stress prevalent in contemporary societies. METHODS: We isolated HYGC from Streptomyces sp. KCB17JA11 and subjected PC12 cells to corticosterone-induced stress. The effects of HYGC were assessed by measuring autophagy and the expression of mitogen-activated protein kinase (MAPK) phosphorylation-related genes. We used established cellular and molecular techniques to analyze protein levels and pathways. RESULTS: HYGC effectively protected cells against corticosterone-induced injury. Specifically, it significantly reduced corticosterone-induced oxidative stress and inhibited the expression of autophagy-related proteins induced by corticosterone, which provided mechanistic insight into the protective effects of HYGC. At the signaling level, HYGC suppressed c-Jun N-terminal kinase and extracellular signal-regulated kinase phosphorylation and p38 activation. CONCLUSIONS: HYGC is a promising candidate to counteract corticosterone-induced apoptosis and oxidative stress. Autophagy and MAPK pathway inhibition contribute to the protective effects of HYGC. Our findings highlight the potential of HYGC as a therapeutic agent for stress-related disorders and serve as a stepping stone for further exploration and development of stress management strategies.

Time-dependent antidepressant-like effects of reelin and ketamine in the repeated-corticosterone model of chronic stress.

There is an urgent need for novel antidepressants, given that approximately 30% of those diagnosed with depression do not respond adequately to first-line treatment. Additionally, monoaminergic-based antidepressants have a substantial therapeutic time-lag, often taking months to reach full therapeutic effect. Ketamine, an N-methyl-d-aspartate receptor (NMDAR) antagonist is the only current effective rapid-acting antidepressant, demonstrating efficacy within hours and lasting up to two weeks with an acute dose. Reelin, an extracellular matrix glycoprotein, has demonstrated rapid-acting antidepressant-like effects at 24 h, however the exact timescale of these effects has not been investigated. To determine the short and long-term effects of reelin, female Long Evans rats (n = 120) underwent a chronic corticosterone (CORT; or vehicle) paradigm (40 mg/kg, 21 days). On day 21, rats were treated with reelin (3µg; i.v.), ketamine (10 mg/kg; i.p.), both reelin and ketamine (same doses), or vehicle (saline). Behavioural and biological effects were then evaluated at 1 h, 6 h, 12 h, and 1 week after treatment. The 1-week cohort continued CORT injections to ensure the effect of chronic stress was not lost. Individually, both reelin and ketamine significantly rescued CORT-induced behaviour and hippocampal reelin expression at all timepoints. Ketamine rescued a decrease in dendritic maturity as induced by CORT. Synergistic effects of reelin and ketamine appeared at 1-week, suggesting a potential additive effect of the antidepressant-like actions. Taken together, this study provides further support for reelin-based therapeutics to develop rapid-acting antidepressant.

Intranasal delivery of paroxetine: A preclinical study on pharmacokinetics, depressive-like behaviour, and neurochemical sex differences.

Treatment of major depressive disorder remains a major unmet clinical need. Given the advantages of intranasal administration for targeted brain delivery, the present study aimed at investigating the pharmacokinetics of paroxetine, after its intranasal instillation and assessing its potential therapeutic effect on female and male mice subjected to unpredictable chronic mild stress (UCMS) protocol. IN administration revealed direct nose-to-brain paroxetine delivery but dose- and sex-dependent differences. Pharmacokinetics was nonlinear and paroxetine concentrations were consistently higher in plasma and brain of male mice. Additionally, UCMS decreased animal preference for sucrose in both male and female mice following acute (p < 0.01) and chronic stress (p < 0.05), suggesting anhedonia. Both male and female mice exhibited depressive-like behavior in the forced swimming test. UCMS females displayed a significantly longer immobility time and shorter climbing time than the control group (p < 0.05), while no differences were found between male mice. Two weeks of paroxetine intranasal administration reduced immobility time and lengthened climbing and swimming time, approaching values similar to those observed in the healthy control group. The therapeutic effect was stronger on female mice. Importantly, melatonin plasma levels were significantly decreased in female mice following UCMS (p < 0.05), while males exhibited heightened corticosterone levels. On the other hand, treatment with IN paroxetine significantly increased corticosterone and melatonin levels in both sexes compared to healthy mice (p < 0.05). Intranasal paroxetine delivery undoubtedly ameliorated the behavioral despair, characteristic of depressive-like animals. Despite its efficiency in male and female mice subjected to UCMS, females were more prone to this novel therapeutic strategy.

Sumatriptan attenuates fear-learning despair induced by social isolation stress in mice: Mediating role of hypothalamic-pituitary-adrenal axis.

OBJECTIVES: Research has demonstrated that chronic stress experienced early in life can lead to impairments in memory and learning. These deficits are attributed to an imbalance in the interaction between glucocorticoids, the end product of the hypothalamic-pituitary-adrenal (HPA) axis, and glucocorticoid receptors in brain regions responsible for mediating memory, such as the hippocampus. This imbalance can result in detrimental conditions like neuroinflammation. The aim of this study was to assess the impact of sumatriptan, a selective agonist for 5-HT 1B/1D receptors, on fear learning capabilities in a chronic social isolation stress model in mice, with a particular focus on the role of the HPA axis. METHODS: Mice were assigned to two opposing conditions, including social condition (SC) and isolated condition (IC) for a duration of five weeks. All mice underwent passive avoidance test, with their subsequent freezing behavior serving as an indicator of fear retrieval. Mice in the IC group were administered either a vehicle, sumatriptan, GR-127935 (a selective antagonist for 5-HT 1B/1D receptors), or a combination of sumatriptan and GR-127935 during the testing sessions. At the end, all mice were sacrificed and samples of their serum and hippocampus were collected for further analysis. RESULTS: Isolation was found to significantly reduce freezing behavior (p<0.001). An increase in the freezing response among IC mice was observed following the administration of varying doses of sumatriptan, as indicated by a one-way ANOVA analysis (p<0.001). However, the mitigating effects of sumatriptan were reversed upon the administration of GR-127935. An ELISA assay conducted before and after the passive avoidance test revealed no significant change in serum corticosterone levels among SC mice. In contrast, a significant increase was observed among IC mice, suggesting hyper-responsiveness of the HPA axis in isolated animals. This hyper-responsiveness was ameliorated following the administration of sumatriptan. Furthermore, both the sumatriptan and SC groups exhibited a similar trend, showing a significant increase in the expression of hippocampal glucocorticoid receptors following the stress of the passive avoidance test. Lastly, the elevated production of inflammatory cytokines (TNF-α, IL-1ß) observed following social isolation was attenuated in the sumatriptan group. CONCLUSION: Sumatriptan improved fear learning probably through modulation of HPA axis and hippocampus neuroinflammation.

Early life nutrient restriction affects hypothalamic-pituitary-interrenal axis gene expression in a diet type-specific manner.

Stressful experiences in early life can alter phenotypic expression later in life. For instance, in vertebrates, early life nutrient restriction can modify later life activity of the hypothalamic-pituitary-adrenal/interrenal axis (the HPI in amphibians), including the up- and downstream regulatory components of glucocorticoid signaling. Early life nutrient restriction can also influence later life behavior and metabolism (e.g., fat accumulation). Yet, less is known about whether nutrient stress-induced carryover effects on HPA/HPI axis regulation can vary across environmental contexts, such as the type of diet on which nutrient restriction occurs. Here, we experimentally address this question using the plains spadefoot toad (Spea bombifrons), whose larvae develop in ephemeral habitats that impose intense competition over access to two qualitatively distinct diet types: detritus and live shrimp prey. Consistent with diet type-specific carryover effects of early life nutrient restriction on later life HPI axis regulation, we found that temporary nutrient restriction at the larval stage reduced juvenile (i.e., post-metamorphic) brain gene expression of an upstream glucocorticoid regulator (corticotropin-releasing hormone) and two downstream regulators (glucocorticoid and mineralocorticoid receptors) only on the shrimp diet. These patterns are consistent with known diet type-specific effects of larval nutrient restriction on juvenile corticosterone and behavior. Additionally, larval nutrient restriction increased juvenile body fat levels. Our study indicates that HPA/HPI axis regulatory responses to nutrient restriction can vary remarkably across diet types. Such diet type-specific regulation of the HPA/HPI axis might provide a basis for developmental or evolutionary decoupling of stress-induced carryover effects.

Father's Absence in the Mongolian gerbil (Meriones unguiculatus) is associated with alterations in paternal behavior, T, cort, presence of ERα, and AR in mPOA/ BNST.

Testosterone (T), estrogen receptor alpha (ERα), and androgen receptor (AR) play a significant role in the regulation of paternal behavior. We determined the effects of deprivation of paternal care on alterations in paternal behavior, T concentrations in plasma, and the presence of ERα and AR in the medial preoptic area (mPOA), bed nucleus of the stria terminalis (BNST), medial amygdala (MeA), and olfactory bulb (OB), as well as the corticosterone (CORT) concentrations in plasma caused by deprivation of paternal care in the Mongolian gerbil (Meriones unguiculatus). Twenty pairs of gerbils were formed; the pups were deprived of paternal care (DPC) in 10 pairs. In another 10 pairs, the pups received paternal care (PC). Ten males raised in DPC condition and 10 males raised in PC conditions were mated with virgin females. When they became fathers, each DPC male and PC male was subjected to tests of paternal behavior on day three postpartum. Blood samples were obtained to quantify T and CORT concentrations, and the brains were removed for ERα and AR immunohistochemistry analyses. DPC males gave less care to their pups than PC males, and they had significantly lower T concentrations and levels of ERα and AR in the mPOA and BNST than PC males. DPC males also had higher CORT concentrations than PC males. These results suggest that in the Mongolian gerbil father's absence causes a decrease in paternal care in the offspring, which is associated with alterations in the neuroendocrine mechanisms that regulate it.