Cognitive deficits and impaired hippocampal long-term potentiation in KATP-induced DEND syndrome.

ATP-sensitive potassium (KATP) gain-of-function (GOF) mutations cause neonatal diabetes, with some individuals exhibiting developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome. Mice expressing KATP-GOF mutations pan-neuronally (nKATP-GOF) demonstrated sensorimotor and cognitive deficits, whereas hippocampus-specific hKATP-GOF mice exhibited mostly learning and memory deficiencies. Both nKATP-GOF and hKATP-GOF mice showed altered neuronal excitability and reduced hippocampal long-term potentiation (LTP). Sulfonylurea therapy, which inhibits KATP, mildly improved sensorimotor but not cognitive deficits in KATP-GOF mice. Mice expressing KATP-GOF mutations in pancreatic ß-cells developed severe diabetes but did not show learning and memory deficits, suggesting neuronal KATP-GOF as promoting these features. These findings suggest a possible origin of cognitive dysfunction in DEND and the need for novel drugs to treat neurological features induced by neuronal KATP-GOF.

Neuronal Nitric Oxide Inhibitor 7-Nitroindazole Improved Brain-Derived Neurotrophic Factor and Attenuated Brain Tissues Oxidative Damage and Learning and Memory Impairments of Hypothyroid Juvenile Rats.

Hypothyroidism-associated learning and memory impairment is reported to be connected to oxidative stress and reduced levels of brain-derived neurotrophic factor (BDNF). The effects of neuronal nitric oxide inhibitor 7-nitroindazole (7NI) on brain tissues oxidative damage, nitric oxide (NO), BDNF and memory impairments in hypothyroid juvenile rats were investigated. Male Wistar juvenile rats (20 days old) were divided into five groups, including Martinez et al. (J Neurochem 78 (5):1054-1063, 2001). Control in which vehicle was injected instead of 7NI, (Jackson in Thyroid 8 (10):951-956, 1998) Propylthiouracil (PTU) where 0.05% PTU was added in drinking water and vehicle was injected instead of 7NI, (Gong et al. in BMC Neurosci 11 (1):50, 2010; Alva-Sánchez et al. in Brain Res 1271:27-35, 2009; Anaeigoudari et al. in Pharmacol Rep 68 (2): 243-249, 2016) PTU-7NI 5, PTU-7NI 10 and PTU-7NI 20 in which 5, 10, or 20 mg/kg7NI was injected intraperitoneally (i.p.). Following 6 weeks, Morris water maze (MMW) and passive avoidance learning (PAL) tests were used to evaluate the memory. Finally, the hippocampus and the cortex of the rats were removed after anesthesia by urethane to be used for future analysis. The escape latency and traveled path in MWM test was increased in PTU group (P < 0.001). PTU also reduced the latency to enter the dark box of PAL and the time spent and the distance in the target quadrant in MWM test (P < 0.001 and P < 0.01). Treatment with 7NI attenuated all adverse effects of PTU (P < 0.05 to P < 0.001). PTU lowered BDNF and thiol content and superoxide dismutase (SOD) and catalase (CAT) activities in the brain but increased malondialdehyde (MDA) and nitric oxide (NO) metabolites. In addition, 7NI improved thiol, SOD, CAT, thiol, and BDNF but attenuated MDA and NO metabolites. The results of the current study showed that 7NI improvement in the learning and memory of the hypothyroid juvenile rats, which was accompanied with improving of BDNF and attenuation of NO and brain tissues oxidative damage.

Effect of Curcuma zedoaria hydro-alcoholic extract on learning, memory deficits and oxidative damage of brain tissue following seizures induced by pentylenetetrazole in rat.

BACKGROUND: Previous studies have shown that seizures can cause cognitive disorders. On the other hand, the Curcuma zedoaria (CZ) has beneficial effects on the nervous system. However, there is little information on the possible effects of the CZ extract on seizures. The aim of this study was to investigate the possible effects of CZ extract on cognitive impairment and oxidative stress induced by epilepsy in rats. METHODS: Rats were randomly divided into different groups. In all rats (except the sham group), kindling was performed by intraperitoneal injection of pentylenetetrazol (PTZ) at a dose of 35 mg/kg every 48 h for 14 days. Positive group received 2 mg/kg diazepam + PTZ; treatment groups received 100, 200 or 400 mg/kg CZ extract + PTZ; and one group received 0.5 mg/kg flumazenil and CZ extract + PTZ. Shuttle box and Morris Water Maze tests were used to measure memory and learning. On the last day of treatments PTZ injection was at dose of 60 mg/kg, tonic seizure threshold and mortality rate were recorded in each group. After deep anesthesia, blood was drawn from the rats' hearts and the hippocampus of all rats was removed. RESULTS: Statistical analysis of the data showed that the CZ extract significantly increased the tonic seizure threshold and reduced the pentylenetetrazol-induced mortality and the extract dose of 400 mg/kg was selected as the most effective dose compared to the other doses. It was also found that flumazenil (a GABAA receptor antagonist) reduced the tonic seizure threshold compared to the effective dose of the extract. The results of shuttle box and Morris water maze behavioral tests showed that memory and learning decreased in the negative control group and the CZ extract treatment improved memory and learning in rats. The CZ extract also increased antioxidant capacity, decreased MDA and NO in the brain and serum of pre-treated groups in compared to the negative control group. CONCLUSION: It is concluded that the CZ extract has beneficial effects on learning and memory impairment in PTZ-induced epilepsy model, which has been associated with antioxidant effects in the brain or possibly exerts its effects through the GABAergic system.

Rescue of Learning and Memory Deficits in the Human Nonsyndromic Intellectual Disability Cereblon Knock-Out Mouse Model by Targeting the AMP-Activated Protein Kinase-mTORC1 Translational Pathway.

A homozygous nonsense mutation in the cereblon (CRBN) gene results in autosomal recessive, nonsyndromic intellectual disability that is devoid of other phenotypic features, suggesting a critical role of CRBN in mediating learning and memory. In this study, we demonstrate that adult male Crbn knock-out (CrbnKO) mice exhibit deficits in hippocampal-dependent learning and memory tasks that are recapitulated by focal knock-out of Crbn in the adult dorsal hippocampus, with no changes in social or repetitive behavior. Cellular studies identify deficits in long-term potentiation at Schaffer collateral CA1 synapses. We further show that Crbn is robustly expressed in the mouse hippocampus and CrbnKO mice exhibit hyperphosphorylated levels of AMPKα (Thr172). Examination of processes downstream of AMP-activated protein kinase (AMPK) finds that CrbnKO mice have a selective impairment in mediators of the mTORC1 translation initiation pathway in parallel with lower protein levels of postsynaptic density glutamatergic proteins and higher levels of excitatory presynaptic markers in the hippocampus with no change in markers of the unfolded protein response or autophagy pathways. Acute pharmacological inhibition of AMPK activity in adult CrbnKO mice rescues learning and memory deficits and normalizes hippocampal mTORC1 activity and postsynaptic glutamatergic proteins without altering excitatory presynaptic markers. Thus, this study identifies that loss of Crbn results in learning, memory, and synaptic defects as a consequence of exaggerated AMPK activity, inhibition of mTORC1 signaling, and decreased glutamatergic synaptic proteins. Thus, CrbnKO mice serve as an ideal model of intellectual disability to further explore molecular mechanisms of learning and memory.SIGNIFICANCE STATEMENT Intellectual disability (ID) is one of the most common neurodevelopmental disorders. The cereblon (CRBN) gene has been linked to autosomal recessive, nonsyndromic ID, characterized by an intelligence quotient between 50 and 70 but devoid of other phenotypic features, making cereblon an ideal protein for the study of the fundamental aspects of learning and memory. Here, using the cereblon knock-out mouse model, we show that cereblon deficiency disrupts learning, memory, and synaptic function via AMP-activated protein kinase hyperactivity, downregulation of mTORC1, and dysregulation of excitatory synapses, with no changes in social or repetitive behaviors, consistent with findings in the human population. This establishes the cereblon knock-out mouse as a model of pure ID without the confounding behavioral phenotypes associated with other current models of ID.

Fluoxetine reverses brain radiation and temozolomide-induced anxiety and spatial learning and memory defect in mice.

Radiation therapy and concomitant temozolomide chemotherapy are commonly used in treatment of brain tumors, but they may also result in behavioral impairments such as anxiety and cognitive deficit. The present study sought to investigate the effect of fluoxetine on the behavioral impairments caused by radiation and temozolomide treatment. C57BL/6J mice were subjected to a single cranial radiation followed by 6-wk cyclic temozolomide administration and were then treated with chronic administration of fluoxetine. Behavioral tests were carried out to determine the anxiety-like behavior and cognition function of these animals. Long-term potentiation (LTP) in the hippocampus was measured by electrophysiology, and neurogenesis in the dentate gyrus was evaluated by immunohistochemistry. Mice treated with radiation and temozolomide showed increased anxiety-like behavior and cognitive impairment, along with LTP impairment and neurogenesis deficit. Chronic fluoxetine administration could reverse the behavioral dysfunction, enhance LTP, and increase neurogenesis in the hippocampus. NEW & NOTEWORTHY Mice treated with radiation and temozolomide showed increased anxiety-like behavior and cognitive impairment. Chronic fluoxetine administration could reverse the behavioral dysfunction. The effect of fluoxetine might be via rescuing the neurogenesis deficit caused by radiation and temozolomide treatment.

Inhibition of c-Jun N-Terminal Kinase Protects Against Brain Damage and Improves Learning and Memory After Traumatic Brain Injury in Adult Mice.

Traumatic brain injury (TBI) is a global risk factor that leads to long-term cognitive impairments. To date, the disease remains without effective therapeutics because of the multifactorial nature of the disease. Here, we demonstrated that activation of the c-Jun N-terminal kinase (JNK) is involved in multiple pathological features of TBI. Therefore, we investigated the disease-modifying therapeutic potential of JNK-specific inhibitor (SP600125) in TBI mice. Treating 2 different models of TBI mice with SP600125 for 7 days dramatically inhibited activated JNK, resulting in marked reductions of amyloid precursor protein (APP) expression level and in amyloid beta production and hyperphosphorylated tau and regulation of the abnormal expression of secretases. Furthermore, SP600125 strongly inhibited inflammatory responses, blood-brain barrier breakdown, apoptotic neurodegeneration, and synaptic protein loss, regulated prosurvival processes and improved motor function and behavioral outcomes in TBI mice. More interestingly, we found that SP600125 treatment ameliorated amyloidogenic APP processing and promoted the nonamyloidogenic pathway in TBI mouse brains. Our findings strongly suggest that active JNK is critically involved in disease development after TBI and that inhibition of JNK with SP600125 is highly efficient for slowing disease progression by reducing multiple pathological features in TBI mouse brains and regulating cognitive dysfunction.

Surgical incision induces learning impairment in mice partially through inhibition of the brain-derived neurotrophic factor signaling pathway in the hippocampus and amygdala.

Surgical incision-induced nociception contributes to the occurrence of postoperative cognitive dysfunction. However, the exact mechanisms involved remain unclear. Brain-derived neurotrophic factor (BDNF) has been demonstrated to improve fear learning ability. In addition, BDNF expression is influenced by the peripheral nociceptive stimulation. Therefore, we hypothesized that surgical incision-induced nociception may cause learning impairment by inhibiting the BDNF/tropomyosin-related kinase B (TrkB) signaling pathway. The fear conditioning test, enzyme-linked immunosorbent assay, and Western blot analyses were used to confirm our hypothesis and determine the effect of a plantar incision on the fear learning and the BDNF/TrkB signaling pathway in the hippocampus and amygdala. The freezing times in the context test and the tone test were decreased after the plantar incision. A eutectic mixture of local anesthetics attenuated plantar incision-induced postoperative pain and fear learning impairment. ANA-12, a selective TrkB antagonist, abolished the improvement in fear learning and the activation of the BDNF signaling pathway induced by eutectic mixture of local anesthetics. Based on these results, surgical incision-induced postoperative pain, which was attenuated by postoperative analgesia, caused learning impairment in mice partially by inhibiting the BDNF signaling pathway. These findings provide insights into the mechanism underlying surgical incision-induced postoperative cognitive function impairment.

Combined effect of non-bacteriolytic antibiotic and inhibition of matrix metalloproteinases prevents brain injury and preserves learning, memory and hearing function in experimental paediatric pneumococcal meningitis.

BACKGROUND: Pneumococcal meningitis is associated with high mortality and morbidity rates. Up to 50% of survivors show neurologic sequelae including hearing loss, cognitive impairments and learning disabilities, being particularly detrimental in affected infants and children where adjuvant therapy with dexamethasone has no proven beneficial effect. We evaluated the effect of concomitantly targeting specific pathophysiological mechanisms responsible for brain damage-i.e. matrix-metalloproteinase (MMP) activity and the exacerbated cerebral inflammation provoked through antibiotic-induced bacterial lysis. Here, we combined adjunctive therapies previously shown to be neuroprotective when used as single adjuvant therapies. METHODS: Eleven-day-old Wistar rats were infected intracisternally with 6.44 ± 2.17 × 103 CFU Streptococcus pneumoniae and randomised for treatment with ceftriaxone combined with (a) single adjuvant therapy with daptomycin (n = 24), (b) single adjuvant therapy with Trocade (n = 24), (c) combined adjuvant therapy (n = 66) consisting of daptomycin and Trocade, or (d) ceftriaxone monotherapy (n = 42). Clinical parameters and inflammatory CSF cytokine levels were determined during acute meningitis. Cortical damage and hippocampal apoptosis were assessed 42 h after infection. Morris water maze and auditory brainstem responses were used to assess neurofunctional outcome 3 weeks after infection. RESULTS: We found significantly reduced apoptosis in the hippocampal subgranular zone in infant rats receiving adjuvant Trocade (p < 0.01) or combined adjuvant therapy (p < 0.001). Cortical necrosis was significantly reduced in rats treated with adjuvant daptomycin (p < 0.05) or combined adjuvant therapy (p < 0.05) compared to ceftriaxone monotherapy. Six hours after treatment initiation, CSF cytokine levels were significantly reduced for TNF-α (p < 0.01), IL-1ß (p < 0.01), IL-6 (p < 0.001) and IL-10 (p < 0.01) in animals receiving combined adjuvant intervention compared to ceftriaxone monotherapy. Importantly, combined adjuvant therapy significantly improved learning and memory performance in infected animals and reduced hearing loss (77.14 dB vs 60.92 dB, p < 0.05) by preserving low frequency hearing capacity, compared to ceftriaxone monotherapy. CONCLUSION: Combined adjuvant therapy with the non-bacteriolytic antibiotic daptomycin and the MMP inhibitor Trocade integrates the neuroprotective effects of both single adjuvants in experimental paediatric pneumococcal meningitis by reducing neuroinflammation and brain damage, thereby improving neurofunctional outcome. This strategy represents a promising therapeutic option to improve the outcome of paediatric patients suffering from pneumococcal meningitis.

Alcohol improves cerebellar learning deficit in myoclonus-dystonia: A clinical and electrophysiological investigation.

OBJECTIVE: To characterize neurophysiological subcortical abnormalities in myoclonus-dystonia and their modulation by alcohol administration. METHODS: Cerebellar associative learning and basal ganglia-brainstem interaction were investigated in 17 myoclonus-dystonia patients with epsilon-sarcoglycan (SGCE) gene mutation and 21 age- and sex-matched healthy controls by means of classical eyeblink conditioning and blink reflex recovery cycle before and after alcohol intake resulting in a breath alcohol concentration of 0.08% (0.8g/l). The alcohol responsiveness of clinical symptoms was evaluated by 3 blinded raters with a standardized video protocol and clinical rating scales including the Unified Myoclonus Rating Scale and the Burke-Fahn-Marsden Dystonia Rating Scale. RESULTS: Patients showed a significantly reduced number of conditioned eyeblink responses before alcohol administration compared to controls. Whereas the conditioning response rate decreased under alcohol intake in controls, it increased in patients (analysis of variance: alcohol state × group, p = 0.004). Blink reflex recovery cycle before and after alcohol intake did not differ between groups. Myoclonus improved significantly after alcohol intake (p = 0.016). The severity of action myoclonus at baseline correlated negatively with the conditioning response in classical eyeblink conditioning in patients. INTERPRETATION: The combination of findings of reduced baseline acquisition of conditioned eyeblink responses and normal blink reflex recovery cycle in patients who improved significantly with alcohol intake suggests a crucial role of cerebellar networks in the generation of symptoms in these patients. Ann Neurol 2017;82:543-553.

Modulation of GSK-3ß/ß-Catenin Signaling Contributes to Learning and Memory Impairment in a Rat Model of Depression.

Background: It is widely accepted that cognitive processes, such as learning and memory, are affected in depression, but the molecular mechanisms underlying the interactions of these 2 disorders are not clearly understood. Recently, glycogen synthase kinase-3 beta (GSK-3ß)/ß-catenin signaling was shown to play an important role in the regulation of learning and memory. Methods: The present study used a rat model of depression, chronic unpredictable stress, to determine whether hippocampal GSK-3ß/ß-catenin signaling was involved in learning and memory alterations. Results: Our results demonstrated that chronic unpredictable stress had a dramatic influence on spatial cognitive performance in the Morris water maze task and reduced the phosphorylation of Ser9 of GSK-3ß as well as the total and nuclear levels of ß-catenin in the hippocampus. Inhibition of GSK3ß by SB216763 significantly ameliorated the cognitive deficits induced by chronic unpredictable stress, while overexpression of GSK3ß by AAV-mediated gene transfer significantly decreased cognitive performance in adult rats. In addition, chronic unpredictable stress exposure increased the expression of the canonical Wnt antagonist Dkk-1. Furthermore, chronic administration of corticosterone significantly increased Dkk-1 expression, decreased the phosphorylation of Ser9 of GSK-3ß, and resulted in the impairment of hippocampal learning and memory. Conclusions: Our results indicate that impairment of learning and memory in response to chronic unpredictable stress may be attributed to the dysfunction of GSK-3ß/ß-catenin signaling mediated by increased glucocorticoid signaling via Dkk-1.

Potential learning and memory disruptors and enhancers in a simple, 1-day operant task in mice.

The objective of this study was to develop a rapid, 1-day learning and memory assay in mice that is sensitive to the effects of compounds that could impair or enhance acquisition and retrieval. Swiss-Webster, male mice were placed in experimental chambers for a 1-h acquisition session with an intermittent, audible tone. If a nose-poke response occurred during the tone, an Ensure water solution was presented. After 1 h, the mice returned to the chambers for 2 h. Drugs were injected before or after sessions to determine the effects on acquisition and/or retrieval. Mice injected with saline learned a nose-poke response as measured by decreased latencies to earn 10 reinforcers, increased reinforced response rates, and decreased nonreinforced response rates. Scopolamine and acetazolamide impaired retrieval of the nose-poke response, whereas ketamine only modestly impaired retrieval. Doses of 8-OH-DPAT or the novel carbonic anhydrase activator, MAI27, either had no effect or impaired some measures of responding. Neither 8-OH-DPAT nor MAI27 were able to prevent the modest impairments produced by ketamine. The simple, 1-day operant task is a rapid assay that can be used as an initial screen to test the effects of learning and memory disruptors and potentially enhancers.

α2* Nicotinic acetylcholine receptors influence hippocampus-dependent learning and memory in adolescent mice.

The absence of α2* nicotinic acetylcholine receptors (nAChRs) in oriens lacunosum moleculare (OLM) GABAergic interneurons ablate the facilitation of nicotine-induced hippocampal CA1 long-term potentiation and impair memory. The current study delineated whether genetic mutations of α2* nAChRs (Chrna2L9'S/L9'S and Chrna2KO) influence hippocampus-dependent learning and memory and CA1 synaptic plasticity. We substituted a serine for a leucine (L9'S) in the α2 subunit (encoded by the Chrna2 gene) to make a hypersensitive nAChR. Using a dorsal hippocampus-dependent task of preexposure-dependent contextual fear conditioning, adolescent hypersensitive Chrna2L9'S/L9'S male mice exhibited impaired learning and memory. The deficit was rescued by low-dose nicotine exposure. Electrophysiological studies demonstrated that hypersensitive α2 nAChRs potentiate acetylcholine-induced ion channel flux in oocytes and acute nicotine-induced facilitation of dorsal/intermediate CA1 hippocampal long-term potentiation in Chrna2L9'S/L9'S mice. Adolescent male mice null for the α2 nAChR subunit exhibited a baseline deficit in learning that was not reversed by an acute dose of nicotine. These effects were not influenced by locomotor, sensory or anxiety-related measures. Our results demonstrated that α2* nAChRs influenced hippocampus-dependent learning and memory, as well as nicotine-facilitated CA1 hippocampal synaptic plasticity.

Violent incidents in a secure service for individuals with learning disabilities: Incident types, circumstances and staff responses.

BACKGROUND: The issue of violence in secure services has long been recognized both in the UK and worldwide. However, there is currently scarce literature available about violence within learning disability (LD) secure settings. METHODS: Secondary data analysis was conducted on violent incidents, using information routinely collected by the staff over a 1-year period. RESULTS: Physical assaults were the most frequent type of incident, and the distribution in terms of days or months was homogenous and incidents were concentrated in the corridors, lounges and dining rooms of secure facilities. Antipsychotic medication was not regularly prescribed. Generalized linear modelling analyses revealed significant predictors that increased the chances of seclusion and physical restraint, such as being female or directing the violence towards staff. CONCLUSIONS: These findings can inform staff training on violence prevention and suggest that increased ward-based supervision and enhanced use of psychological formulations may help in reducing violence within this service context.

Edaravone injection reverses learning and memory deficits in a rat model of vascular dementia.

Edaravone is a novel free radical scavenger that exerts neuroprotective effects by inhibiting endothelial injury and by ameliorating neuronal damage in brain ischemia. Recently, it was reported that edaravone could alleviate the pathology and cognitive deficits of Alzheimer's disease patients. However, its relevance to vascular dementia (VaD) is not clear. In this study, we partially occluded the bilateral carotid arteries of rats surgically to induce chronic cerebral hypoperfusion (CCH), a well-known rat model of VaD. Water maze and step-down inhibitory test were used to evaluate the memory deficit. The activities of superoxide dismutase (SOD) and lactate dehydrogenase (LDH), the content of malondialdehyde (MDA) and total reactive oxygen species were measured to evaluate the oxidative stress level. Western blot analysis was used to evaluate the synaptic protein expression. It was found that treatment with edaravone for a 5-week period was able to reverse both spatial and fear-memory deficits in rats with CCH. Edaravone significantly reduced the level of oxidative stress in the brains of rats with CCH by increasing SOD activity and decreasing the content of MDA, LDH, and total reactive oxygen species. Furthermore, edaravone treatment also restored the levels of multiple synaptic proteins in the hippocampi of rats with CCH. Our data provide direct evidence supporting the neuroprotective effects of edaravone in VaD. We propose that the alleviation of oxidative stress and restoration of synaptic proteins play important roles in neuroprotection.

Re-Opening the Critical Window for Estrogen Therapy.

A decline in estradiol (E2)-mediated cognitive benefits denotes a critical window for the therapeutic effects of E2, but the mechanism for closing of the critical window is unknown. We hypothesized that upregulating the expression of estrogen receptor α (ERα) or estrogen receptor ß (ERß) in the hippocampus of aged animals would restore the therapeutic potential of E2 treatments and rejuvenate E2-induced hippocampal plasticity. Female rats (15 months) were ovariectomized, and, 14 weeks later, adeno-associated viral vectors were used to express ERα, ERß, or green fluorescent protein (GFP) in the CA1 region of the dorsal hippocampus. Animals were subsequently treated for 5 weeks with cyclic injections of 17ß-estradiol-3-benzoate (EB, 10 µg) or oil vehicle. Spatial memory was examined 48 h after EB/oil treatment. EB treatment in the GFP (GFP + EB) and ERß (ERß + EB) groups failed to improve episodic spatial memory relative to oil-treated animals, indicating closing of the critical window. Expression of ERß failed to improve cognition and was associated with a modest learning impairment. Cognitive benefits were specific to animals expressing ERα that received EB treatment (ERα + EB), such that memory was improved relative to ERα + oil and GFP + EB. Similarly, ERα + EB animals exhibited enhanced NMDAR-mediated synaptic transmission compared with the ERα + oil and GFP + EB groups. This is the first demonstration that the window for E2-mediated benefits on cognition and hippocampal E2 responsiveness can be reinstated by increased expression of ERα. SIGNIFICANCE STATEMENT: Estradiol is neuroprotective, promotes synaptic plasticity in the hippocampus, and protects against cognitive decline associated with aging and neurodegenerative diseases. However, animal models and clinical studies indicate a critical window for the therapeutic treatment such that the beneficial effects are lost with advanced age and/or with extended hormone deprivation. We used gene therapy to upregulate expression of the estrogen receptors ERα and ERß and demonstrate that the window for estradiol's beneficial effects on memory and hippocampal synaptic function can be reinstated by enhancing the expression of ERα. Our findings suggest that the activity of ERα controls the therapeutic window by regulating synaptic plasticity mechanisms involved in memory.

Prepubertal castration-associated developmental changes in sigma-1 receptor gene expression levels regulate hippocampus area CA1 activity during adolescence.

The functional relevance of sigma-1 (σ1 ) receptor expression in the rat hippocampal CA1 during adolescence (i.e., 35-60 days old) was explored. A selective antagonist for the σ1 receptor subtype, BD-1047, was applied to study hippocampal long-term potentiation (LTP) and spatial learning performance. Changes in the expression of the σ1 receptor subtype and its function were compared between castrated and sham-castrated rats. Castration reduced the magnitude of both field excitatory postsynaptic potential (fEPSP)-LTP and population spike (PS)-LTP at 35 days (d). BD-1047 decreased PS-LTP in sham-castrated rats, whereas BD-1047 reversed the effect of castration on fEPSP-LTP at 35 d. In addition, BD1047 impaired spatial learning and augmented σ1 receptor mRNA levels in castrated rats at 35 d. Surprisingly, neither castration nor BD1047 had an effect on fEPSP-LTP and PS-LTP, spatial learning ability or gene expression levels at 45 d. Castration had no effect on fEPSP-LTP but reduced PS-LTP at 60 d. BD1047 increased the magnitude of fEPSP-LTP, but had no effect on PS-LTP in castrated rats at 60 d. However, BD1047 reduced spatial learning ability, and σ1 receptor mRNA levels were decreased in castrated rats at 60 d. This study shows that σ1 receptors play a role in the regulation of both CA1 synaptic efficacy and spatial learning performance. The regulatory role of σ1 receptors in activity-dependent CA1-LTP is locality- and age-dependent, whereas its role in spatial learning ability is only age-dependent. Prepubertal castration-associated changes in the expression and function of the σ1 receptor during adolescence may play a developmental role in the regulation of hippocampal area CA1 activity and plasticity. © 2016 Wiley Periodicals, Inc.

Infliximab reduces peripheral inflammation, neuroinflammation, and extracellular GABA in the cerebellum and improves learning and motor coordination in rats with hepatic encephalopathy.

BACKGROUND: Peripheral inflammation contributes to the neurological alterations in hepatic encephalopathy (HE). Neuroinflammation and altered GABAergic neurotransmission mediate cognitive and motor alterations in rats with HE. It remains unclear (a) if neuroinflammation and neurological impairment in HE are a consequence of peripheral inflammation and (b) how neuroinflammation impairs GABAergic neurotransmission. The aims were to assess in rats with HE whether reducing peripheral inflammation with anti-TNF-α (1) prevents cognitive impairment and motor in-coordination, (2) normalizes neuroinflammation and extracellular GABA in the cerebellum and also (3) advances the understanding of mechanisms linking neuroinflammation and increased extracellular GABA. METHODS: Rats with HE due to portacaval shunt (PCS) were treated with infliximab. Astrocytes and microglia activation and TNF-α and IL-1ß were analyzed by immunohistochemistry. Membrane expression of the GABA transporters GAT-3 and GAT-1 was analyzed by cross-linking with BS3. Extracellular GABA was analyzed by microdialysis. Motor coordination was tested using the beam walking and learning ability using the Y maze task. RESULTS: PCS rats show peripheral inflammation, activated astrocytes, and microglia and increased levels of TNF-α and IL-1ß. Membrane expression of GAT-3 and extracellular GABA are increased, leading to impaired motor coordination and learning ability. Infliximab reduces peripheral inflammation, microglia, and astrocyte activation and neuroinflammation and normalizes GABAergic neurotransmission, motor coordination, and learning ability. CONCLUSIONS: Neuroinflammation is associated with altered GABAergic neurotransmission and increased GAT-3 membrane expression and extracellular GABA (a); peripheral inflammation is a main contributor to the impairment of motor coordination and of the ability to learn the Y maze task in PCS rats (b); and reducing peripheral inflammation using safe procedures could be a new therapeutic approach to improve cognitive and motor function in patients with HE

Hyperammonemia induces glial activation, neuroinflammation and alters neurotransmitter receptors in hippocampus, impairing spatial learning: reversal by sulforaphane.

BACKGROUND: Patients with liver cirrhosis and minimal hepatic encephalopathy (MHE) show mild cognitive impairment and spatial learning dysfunction. Hyperammonemia acts synergistically with inflammation to induce cognitive impairment in MHE. Hyperammonemia-induced neuroinflammation in hippocampus could contribute to spatial learning impairment in MHE. Two main aims of this work were: (1) to assess whether chronic hyperammonemia increases inflammatory factors in the hippocampus and if this is associated with microglia and/or astrocytes activation and (2) to assess whether hyperammonemia-induced neuroinflammation in the hippocampus is associated with altered membrane expression of glutamate and GABA receptors and spatial learning impairment. There are no specific treatments for cognitive alterations in patients with MHE. A third aim was to assess whether treatment with sulforaphane enhances endogenous the anti-inflammatory system, reduces neuroinflammation in the hippocampus of hyperammonemic rats, and restores spatial learning and if normalization of receptor membrane expression is associated with learning improvement. METHODS: We analyzed the following in control and hyperammonemic rats, treated or not with sulforaphane: (1) microglia and astrocytes activation by immunohistochemistry, (2) markers of pro-inflammatory (M1) (IL-1ß, IL-6) and anti-inflammatory (M2) microglia (Arg1, YM-1) by Western blot, (3) membrane expression of GABA, AMPA, and NMDA receptors using the BS3 cross-linker, and (4) spatial learning using the radial maze. RESULTS: The results reported show that hyperammonemia induces astrocytes and microglia activation in the hippocampus, increasing pro-inflammatory cytokines IL-1ß and IL-6. This is associated with altered membrane expression of AMPA, NMDA, and GABA receptors which would be responsible for altered neurotransmission and impairment of spatial learning in the radial maze. Treatment with sulforaphane promotes microglia differentiation from pro-inflammatory M1 to anti-inflammatory M2 phenotype and reduces activation of astrocytes in hyperammonemic rats. This reduces neuroinflammation, normalizes membrane expression of glutamate and GABA receptors, and restores spatial learning in hyperammonemic rats. CONCLUSIONS: Hyperammonemia-induced neuroinflammation impairs glutamatergic and GABAergic neurotransmission by altering membrane expression of glutamate and GABA receptors, resulting in impaired spatial learning. Sulforaphane reverses all these effects. Treatment with sulforaphane could be useful to improve cognitive function in cirrhotic patients with minimal or clinical hepatic encephalopathy.

Neuroprotective effects of bee venom phospholipase A2 in the 3xTg AD mouse model of Alzheimer's disease.

BACKGROUND: Alzheimer's disease (AD) is a severe neuroinflammatory disease. CD4(+)Foxp3(+) regulatory T cells (Tregs) modulate various inflammatory diseases via suppressing Th cell activation. There are increasing evidences that Tregs have beneficial roles in neurodegenerative diseases. Previously, we found the population of Treg cells was significantly increased by bee venom phospholipase A2 (bvPLA2) treatment in vivo and in vitro. METHODS: To examine the effects of bvPLA2 on AD, bvPLA2 was administered to 3xTg-AD mice, mouse model of Alzheimer's disease. The levels of amyloid beta (Aß) deposits in the hippocampus, glucose metabolism in the brain, microglia activation, and CD4(+) T cell infiltration were analyzed to evaluate the neuroprotective effect of bvPLA2. RESULTS: bvPLA2 treatment significantly enhanced the cognitive function of the 3xTg-AD mice and increased glucose metabolism, as assessed with 18F-2 fluoro-2-deoxy-D-glucose ([F-18] FDG) positron emission tomography (PET). The levels of Aß deposits in the hippocampus were dramatically decreased by bvPLA2 treatment. This neuroprotective effect of bvPLA2 was associated with microglial deactivation and reduction in CD4(+) T cell infiltration. Interestingly, the neuroprotective effects of bvPLA2 were abolished in Treg-depleted mice. CONCLUSIONS: The present studies strongly suggest that the increase of Treg population by bvPLA2 treatment might inhibit progression of AD in the 3xTg AD mice.

Midazolam-ketamine dual therapy stops cholinergic status epilepticus and reduces Morris water maze deficits.

OBJECTIVE: Pharmacoresistance remains an unsolved therapeutic challenge in status epilepticus (SE) and in cholinergic SE induced by nerve agent intoxication. SE triggers a rapid internalization of synaptic γ-aminobutyric acid A (GABAA ) receptors and externalization of N-methyl-d-aspartate (NMDA) receptors that may explain the loss of potency of standard antiepileptic drugs (AEDs). We hypothesized that a drug combination aimed at correcting the consequences of receptor trafficking would reduce SE severity and its long-term consequences. METHODS: A severe model of SE was induced in adult Sprague-Dawley rats with a high dose of lithium and pilocarpine. The GABAA receptor agonist midazolam, the NMDA receptor antagonist ketamine, and/or the AED valproate were injected 40 min after SE onset in combination or as monotherapy. Measures of SE severity were the primary outcome. Secondary outcomes were acute neuronal injury, spontaneous recurrent seizures (SRS), and Morris water maze (MWM) deficits. RESULTS: Midazolam-ketamine dual therapy was more efficient than double-dose midazolam or ketamine monotherapy or than valproate-midazolam or valproate-ketamine dual therapy in reducing several parameters of SE severity, suggesting a synergistic mechanism. In addition, midazolam-ketamine dual therapy reduced SE-induced acute neuronal injury, epileptogenesis, and MWM deficits. SIGNIFICANCE: This study showed that a treatment aimed at correcting maladaptive GABAA receptor and NMDA receptor trafficking can stop SE and reduce its long-term consequences. Early midazolam-ketamine dual therapy may be superior to monotherapy in the treatment of benzodiazepine-refractory SE.