2-AG-Mediated Control of GABAergic Signaling Is Impaired in a Model of Epilepsy.

Repeated seizures result in a persistent maladaptation of endocannabinoid (eCB) signaling, mediated part by anandamide signaling deficiency in the basolateral amygdala (BLA) that manifests as aberrant synaptic function and altered emotional behavior. Here, we determined the effect of repeated seizures (kindling) on 2-arachidonoylglycerol (2-AG) signaling on GABA transmission by directly measuring tonic and phasic eCB-mediated retrograde signaling in an in vitro BLA slice preparation from male rats. We report that both activity-dependent and muscarinic acetylcholine receptor (mAChR)-mediated depression of GABA synaptic transmission was reduced following repeated seizure activity. These effects were recapitulated in sham rats by preincubating slices with the 2-AG synthesizing enzyme inhibitor DO34. Conversely, preincubating slices with the 2-AG degrading enzyme inhibitor KML29 rescued activity-dependent 2-AG signaling, but not mAChR-mediated synaptic depression, over GABA transmission in kindled rats. These effects were not attributable to a change in cannabinoid type 1 (CB1) receptor sensitivity or altered 2-AG tonic signaling since the application of the highly selective CB1 receptor agonist CP55,940 provoked a similar reduction in GABA synaptic activity in both sham and kindled rats, while no effect of either DO34 or of the CB1 inverse agonist AM251 was observed on frequency and amplitude of spontaneous IPSCs in either sham or kindled rats. Collectively, these data provide evidence that repeated amygdala seizures persistently alter phasic 2-AG-mediated retrograde signaling at BLA GABAergic synapses, probably by impairing stimulus-dependent 2-AG synthesis/release, which contributes to the enduring aberrant synaptic plasticity associated with seizure activity.SIGNIFICANCE STATEMENT The plastic reorganization of endocannabinoid (eCB) signaling after seizures and during epileptogenesis may contribute to the negative neurobiological consequences associated with seizure activity. Therefore, a deeper understanding of the molecular basis underlying the pathologic long-term eCB signaling remodeling following seizure activity will be crucial to the development of novel therapies for epilepsy that not only target seizure activity, but, most importantly, the epileptogenesis and the comorbid conditions associated with epilepsy.

Stress-induced modulation of endocannabinoid signaling leads to delayed strengthening of synaptic connectivity in the amygdala.

Even a brief exposure to severe stress strengthens synaptic connectivity days later in the amygdala, a brain area implicated in the affective symptoms of stress-related psychiatric disorders. However, little is known about the synaptic signaling mechanisms during stress that eventually culminate in its delayed impact on the amygdala. Hence, we investigated early stress-induced changes in amygdalar synaptic signaling in order to prevent its delayed effects. Whole-cell recordings in basolateral amygdala (BLA) slices from rats revealed higher frequency of miniature excitatory postsynaptic currents (mEPSCs) immediately after 2-h immobilization stress. This was replicated by inhibition of cannabinoid receptors (CB1R), suggesting a role for endocannabinoid (eCB) signaling. Stress also reduced N-arachidonoylethanolamine (AEA), an endogenous ligand of CB1R. Since stress-induced activation of fatty acid amide hydrolase (FAAH) reduces AEA, we confirmed that oral administration of an FAAH inhibitor during stress prevents the increase in synaptic excitation in the BLA soon after stress. Although stress also caused an immediate reduction in synaptic inhibition, this was not prevented by FAAH inhibition. Strikingly, FAAH inhibition during the traumatic stressor was also effective 10 d later on the delayed manifestation of synaptic strengthening in BLA neurons, preventing both enhanced mEPSC frequency and increased dendritic spine-density. Thus, oral administration of an FAAH inhibitor during a brief stress prevents the early synaptic changes that eventually build up to hyperexcitability in the amygdala. This framework is of therapeutic relevance because of growing interest in targeting eCB signaling to prevent the gradual development of emotional symptoms and underlying amygdalar dysfunction triggered by traumatic stress.

Anandamide Signaling Augmentation Rescues Amygdala Synaptic Function and Comorbid Emotional Alterations in a Model of Epilepsy.

Epilepsy is often associated with emotional disturbances and the endocannabinoid (eCB) system tunes synaptic transmission in brain regions regulating emotional behavior. Thus, persistent alteration of eCB signaling after repeated seizures may contribute to the development of epilepsy-related emotional disorders. Here we report that repeatedly eliciting seizures (kindling) in the amygdala caused a long-term increase in anxiety and impaired fear memory retention, which was paralleled by an imbalance in GABA/glutamate presynaptic activity and alteration of synaptic plasticity in the basolateral amygdala (BLA), in male rats. Anandamide (AEA) content was downregulated after repeated seizures, and pharmacological enhancement of AEA signaling rescued seizure-induced anxiety by restoring the tonic control of the eCB signaling over glutamatergic transmission. Moreover, AEA signaling augmentation also rescued the seizure-induced alterations of fear memory by restoring the phasic control of eCB signaling over GABAergic activity and plasticity in the BLA. These results indicate that modulation of AEA signaling represents a potential and promising target for the treatment of comorbid emotional dysfunction associated with epilepsy.SIGNIFICANCE STATEMENT Epilepsy is a heterogeneous neurologic disorder commonly associated with comorbid emotional alterations. However, the management of epilepsy is usually restricted to the control of seizures. The endocannabinoid (eCB) system, particularly anandamide (AEA) signaling, controls neuronal excitability and seizure expression and regulates emotional behavior. We found that repeated seizures cause an allostatic maladaptation of AEA signaling in the amygdala that drives emotional alterations. Boosting AEA signaling through inhibition of its degradative enzyme, fatty acid amide hydrolase (FAAH), restored both synaptic and behavioral alterations. FAAH inhibitors dampen seizure activity in animal models and are used in clinical studies to treat the negative consequences associated with stress. Thereby, they are accessible and can be clinically evaluated to treat both seizures and comorbid conditions associated with epilepsy.

Bacterial Factors That Predict Relapse after Tuberculosis Therapy.

BACKGROUND: Approximately 5% of patients with drug-susceptible tuberculosis have a relapse after 6 months of first-line therapy, as do approximately 20% of patients after 4 months of short-course therapy. We postulated that by analyzing pretreatment isolates of Mycobacterium tuberculosis obtained from patients who subsequently had a relapse or were cured, we could determine any correlations between the minimum inhibitory concentration (MIC) of a drug below the standard resistance breakpoint and the relapse risk after treatment. METHODS: Using data from the Tuberculosis Trials Consortium Study 22 (development cohort), we assessed relapse and cure isolates to determine the MIC values of isoniazid and rifampin that were below the standard resistance breakpoint (0.1 µg per milliliter for isoniazid and 1.0 µg per milliliter for rifampin). We combined this analysis with clinical, radiologic, and laboratory data to generate predictive relapse models, which we validated by analyzing data from the DMID 01-009 study (validation cohort). RESULTS: In the development cohort, the mean (±SD) MIC of isoniazid below the breakpoint was 0.0334±0.0085 µg per milliliter in the relapse group and 0.0286±0.0092 µg per milliliter in the cure group, which represented a higher value in the relapse group by a factor of 1.17 (P=0.02). The corresponding MIC values of rifampin were 0.0695±0.0276 and 0.0453±0.0223 µg per milliliter, respectively, which represented a higher value in the relapse group by a factor of 1.53 (P<0.001). Higher MIC values remained associated with relapse in a multivariable analysis that included other significant between-group differences. In an analysis of receiver-operating-characteristic curves of relapse based on these MIC values, the area under the curve (AUC) was 0.779. In the development cohort, the AUC in a multivariable model that included MIC values was 0.875. In the validation cohort, the MIC values either alone or combined with other patient characteristics were also predictive of relapse, with AUC values of 0.964 and 0.929, respectively. The use of a model score for the MIC values of isoniazid and rifampin to achieve 75.0% sensitivity in cross-validation analysis predicted relapse with a specificity of 76.5% in the development cohort and a sensitivity of 70.0% and a specificity of 100% in the validation cohort. CONCLUSIONS: In pretreatment isolates of M. tuberculosis with decrements of MIC values of isoniazid or rifampin below standard resistance breakpoints, higher MIC values were associated with a greater risk of relapse than lower MIC values. (Funded by the National Institute of Allergy and Infectious Diseases.).

Bound Together: How Psychoanalysis Diminishes Inter-generational DNA Trauma.

The concept of intergenerational transmission of trauma plays a fundamental role in psychoanalysis. While it is known that intergenerational trauma can be transmitted through attachment relationships, a new branch of genetics (epigenetics) has emerged to study the interaction between human behavior and changes in DNA expression. Therefore, psychoanalysis, which has proven to reduce the intergenerational transmission of trauma from a behavioral perspective, can play a positive role in regulating DNA changes caused by environmental stress. The present paper focuses on recent research suggesting a direct correlation between psychological trauma and DNA modifications. In particular, DNA changes caused by psychological trauma can be transmitted from generation to generation, validating the psychoanalytic concept of intergenerational transmission of trauma. This evidence not only supports the essential role psychoanalysis has in influencing human behavior, but also suggests that it affects not only the individuals who undergo it but their offspring, as well, via the epigenetic passage of DNA.

Synergistic action of CB1 and 5-HT2B receptors in preventing pilocarpine-induced status epilepticus in rats.

Endocannabinoids (eCBs) and serotonin (5-HT) play a neuromodulatory role in the central nervous system. Both eCBs and 5-HT regulate neuronal excitability and their pharmacological potentiation has been shown to control seizures in pre-clinical and human studies. Compelling evidence indicates that eCB and 5-HT systems interact to modulate several physiological and pathological brain functions, such as food intake, pain, drug addiction, depression, and anxiety. Nevertheless, there is no evidence of an eCB/5-HT interaction in experimental and human epilepsies, including status epilepticus (SE). Here, we performed video-EEG recording in behaving rats treated with the pro-convulsant agent pilocarpine (PILO), in order to study the effect of the activation of CB1/5-HT2 receptors and their interaction on SE. Synthetic cannabinoid agonist WIN55,212-2 (WIN) decreased behavioral seizure severity of PILO-induced SE at 2 mg/kg (but not at 1 and 5 mg/kg, i.p.), while 5-HT2B/2C receptor agonist RO60-0175 (RO; 1, 3, 10 mg/kg, i.p.) was devoid of any effect. RO 3 mg/kg was instead capable of potentiating the effect of WIN 2 mg/kg on the Racine scale score. Surprisingly, neither WIN 2 mg/kg nor RO 3 mg/kg had any effect on the incidence and the intensity of EEG seizures when administered alone. However, WIN+RO co-administration reduced the incidence and the severity of EEG SE and increased the latency to SE onset after PILO injection. WIN+RO effects were blocked by the selective CB1R antagonist AM251 and the 5-HT2BR antagonist RS127445, but not by the 5-HT2CR antagonist SB242084 or the 5-HT2AR antagonist MDL11,939. These data revealed a synergistic interaction between CB1R/5-HT2BR in the expression of PILO-induced SE.

Postictal hypoperfusion/hypoxia provides the foundation for a unified theory of seizure-induced brain abnormalities and behavioral dysfunction.

A recent article by Farrell et al. characterizes the phenomenon, mechanisms, and treatment of a local and severe hypoperfusion/hypoxia event that occurs in brain regions following a focal seizure. Given the well-established role of cerebral ischemia/hypoxia in brain damage and behavioral dysfunction in other clinical settings (e.g., stroke, cerebral vasospasm), we put forward a new theory: postictal hypoperfusion/hypoxia is responsible for the negative consequences associated with seizures. Fortunately, inhibition of two separate molecular targets, cyclooxygenase-2 (COX-2) and l-type calcium channels, can prevent the expression of postictal hypoperfusion/hypoxia. These inhibitors are important experimental tools used to separate the seizure from the resulting hypoperfusion/hypoxia and can allow researchers to address the contribution of this phenomenon to negative outcomes associated with seizures. Herein we address the implications of this postictal stroke-like event in acute behavioral dysfunction (e.g., Todd's paresis) and sudden unexpected death in epilepsy (SUDEP). Moreover, anatomic alterations such as increased blood-brain barrier permeability, glial activation, central inflammation, and neuronal loss could also be a consequence of repeated hypoperfusion/hypoxic events and, in turn, underlie chronic interictal cognitive and behavioral comorbidities (e.g., memory deficits, anxiety, depression, and psychosis) and exacerbate epileptogenesis. Thus these seemingly disparate and clinically important observations may share a common point of origin: postictal hypoperfusion/hypoxia.

The mycobacterial iron-dependent regulator IdeR induces ferritin (bfrB) by alleviating Lsr2 repression.

Emerging evidence indicates that precise regulation of iron (Fe) metabolism and maintenance of Fe homeostasis in Mycobacterium tuberculosis (Mtb) are essential for its survival and proliferation in the host. IdeR is a central transcriptional regulator of Mtb genes involved in Fe metabolism. While it is well understood how IdeR functions as a repressor, how it induces transcription of a subset of its targets is still unclear. We investigated the molecular mechanism of IdeR-mediated positive regulation of bfrB, the gene encoding the major Fe-storage protein of Mtb. We found that bfrB induction by Fe required direct interaction of IdeR with a DNA sequence containing four tandem IdeR-binding boxes located upstream of the bfrB promoter. Results of in vivo and in vitro transcription assays identified a direct repressor of bfrB, the histone-like protein Lsr2. IdeR counteracted Lsr2-mediated repression in vitro, suggesting that IdeR induces bfrB transcription by antagonizing the repressor activity of Lsr2. Together, these results elucidate the main mechanism of bfrB positive regulation by IdeR and identify Lsr2 as a new factor contributing to Fe homeostasis in mycobacteria.

Antituberculosis thiophenes define a requirement for Pks13 in mycolic acid biosynthesis.

We report a new class of thiophene (TP) compounds that kill Mycobacterium tuberculosis by the previously uncharacterized mechanism of Pks13 inhibition. An F79S mutation near the catalytic Ser55 site in Pks13 conferred TP resistance in M. tuberculosis. Overexpression of wild-type Pks13 resulted in TP resistance, and overexpression of the Pks13(F79S) mutant conferred high resistance. In vitro, TP inhibited fatty acyl-AMP loading onto Pks13. TP inhibited mycolic acid biosynthesis in wild-type M. tuberculosis, but it did so to a much lesser extent in TP-resistant M. tuberculosis. TP treatment was bactericidal and equivalent to treatment with the first-line drug isoniazid, but it was less likely to permit emergent resistance. Combined isoniazid and TP treatment resulted in sterilizing activity. Computational docking identified a possible TP-binding groove within the Pks13 acyl carrier protein domain. This study confirms that M. tuberculosis Pks13 is required for mycolic acid biosynthesis, validates it as a druggable target and demonstrates the therapeutic potential of simultaneously inhibiting multiple targets in the same biosynthetic pathway.

Transfer of a point mutation in Mycobacterium tuberculosis inhA resolves the target of isoniazid.

Isoniazid is one of the most effective antituberculosis drugs, yet its precise mechanism of action is still controversial. Using specialized linkage transduction, a single point mutation allele (S94A) within the putative target gene inhA was transferred in Mycobacterium tuberculosis. The inhA(S94A) allele was sufficient to confer clinically relevant levels of resistance to isoniazid killing and inhibition of mycolic acid biosynthesis. This resistance correlated with the decreased binding of the INH-NAD inhibitor to InhA, as shown by enzymatic and X-ray crystallographic analyses, and establishes InhA as the primary target of isoniazid action in M. tuberculosis.

Generation and Characterization of the First Murine Model of Alzheimer's Disease with Mutated AßPP Inserted in a BALB/c Background (C.B6/J-APPswe).

BACKGROUND: Numerous mouse models of Alzheimer's disease (AD) are available, but all suffer from certain limitations, thus prompting further attempts. To date, no one model exists with amyloidopathy in a BALB/c strain. OBJECTIVE: To generate and characterize the C.B6/J-APPswe mouse, a model of AD with a mutated human gene for the amyloid-ß protein precursor (AßPP) inserted in a BALB/c background. METHODS: We analyzed five groups at different ages (3, 6, 9, 12, and 16-18 months) of C.B6/J-APPswe and wild-type mice (50% males and 50% females) for the main hallmarks of AD by western blotting, amyloid-ß (Aß) ELISA, immunocytochemistry, electrophysiology, and behavioral tests. RESULTS: The C.B6/J-APPswe mouse displays early AßPP and Aß production, late amyloid plaques formation, high level of Tau phosphorylation, synaptic deficits (reduced density and functional impairment due to a reduced post-synaptic responsiveness), neurodegeneration caused by apoptosis and necroptosis/necrosis, microgliosis, astrocytic abnormalities, and sex-related differences in explorative behavior, anxiety-like behavior, and spatial long-term and working memories. Social housing is feasible despite the intra-cage aggressiveness of male animals. CONCLUSION: C.B6/J-APPswe mice develop most of the distinctive features of AD and is a suitable model for the study of brain atrophy mechanisms and of the differences between males and females in the onset of cognitive/non-cognitive deficits.

Sudden unexpected death in epilepsy is prevented by blocking postictal hypoxia.

Epilepsy is at times a fatal disease. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality in people with intractable epilepsy and is defined by exclusion; non-accidental, non-toxicologic, and non-anatomic causes of death. While SUDEP often follows a bilateral tonic-clonic seizure, the mechanisms that ultimately lead to terminal apnea and then asystole remain elusive and there is a lack of preventative treatments. Based on the observation that discrete seizures lead to local and postictal vasoconstriction, resulting in hypoperfusion, hypoxia and behavioural disturbances in the forebrain we reasoned those similar mechanisms may play a role in SUDEP when seizures invade the brainstem. Here we tested this neurovascular-based hypothesis of SUDEP in awake non-anesthetized mice by pharmacologically preventing seizure-induced vasoconstriction, with cyclooxygenase-2 or L-type calcium channel antagonists. In both acute and chronic mouse models of seizure-induced premature mortality, ibuprofen and nicardipine extended life while systemic drug levels remained high enough to be effective. We also examined the potential role of spreading depolarization in the acute model of seizure-induced premature mortality. These data provide a proof-of-principle for the neurovascular hypothesis of SUDEP rather than spreading depolarization and the use of currently available drugs to prevent it.

Nicotine modulation of the lateral habenula/ventral tegmental area circuit dynamics: An electrophysiological study in rats.

Nicotine, the addictive component of tobacco, has bivalent rewarding and aversive properties. Recently, the lateral habenula (LHb), a structure that controls ventral tegmental area (VTA) dopamine (DA) function, has attracted attention as it is potentially involved in the aversive properties of drugs of abuse. Hitherto, the LHb-modulation of nicotine-induced VTA neuronal activity in vivo is unknown. Using standard single-extracellular recording in anesthetized rats, we observed that intravenous administration of nicotine hydrogen tartrate (25-800 µg/kg i.v.) caused a dose-dependent increase in the basal firing rate of the LHb neurons of nicotine-naïve rats. This effect underwent complete desensitization in chronic nicotine (6 mg/kg/day for 14 days)-treated animals. As previously reported, acute nicotine induced an increase in the VTA DA neuronal firing rate. Interestingly, only neurons located medially (mVTA) but not laterally (latVTA) within the VTA were responsive to acute nicotine. This pattern of activation was reversed by chronic nicotine exposure which produced the selective increase of latVTA neuronal activity. Acute lesion of the LHb, similarly to chronic nicotine treatment, reversed the pattern of DA cell activation induced by acute nicotine increasing latVTA but not mVTA neuronal activity. Our evidence indicates that LHb plays an important role in mediating the effects of acute and chronic nicotine within the VTA by activating distinct subregional responses of DA neurons. The LHb/VTA modulation might be part of the neural substrate of nicotine aversive properties. By silencing the LHb chronic nicotine could shift the balance of motivational states toward the reward.

Endocannabinoid-serotonin systems interaction in health and disease.

Endocannabinoid (eCB) and serotonin (5-HT) neuromodulatory systems work both independently and together to finely orchestrate neuronal activity throughout the brain to strongly sculpt behavioral functions. Surprising parallelism between the behavioral effects of 5-HT and eCB activity has been widely reported, including the regulation of emotional states, stress homeostasis, cognitive functions, food intake and sleep. The distribution pattern of the 5-HT system and the eCB molecular elements in the brain display a strong overlap and several studies report a functional interplay and even a tight interdependence between eCB/5-HT signaling. In this review, we examine the available evidence of the interaction between the eCB and 5-HT systems. We first introduce the eCB system, then we describe the eCB/5-HT crosstalk at the neuronal and synaptic levels. Finally, we explore the potential eCB/5-HT interaction at the behavioral level with the implication for psychiatric and neurological disorders. The precise elucidation of how this neuromodulatory interaction dynamically regulates biological functions may lead to the development of more targeted therapeutic strategies for the treatment of depressive and anxiety disorders, psychosis and epilepsy.

The impact of chronic daily nicotine exposure and its overnight withdrawal on the structure of anxiety-related behaviors in rats: Role of the lateral habenula.

Tobacco smoking is a serious health problem worldwide and a leading cause of mortality. Nicotine, the addictive component of tobacco, affects a range of emotional responses, including anxiety-related behaviors. Although perceived by smokers to be anxiolytic, evidence suggests that smoking increases anxiety and that mood fluctuates with nicotine intake. Thus, nicotine addiction may depend on easing the psychobiological distress caused by its abuse. The lateral habenula (LHb) has been implicated as a neural substrate for acute nicotine-induced anxiety, but its role in anxiety-like behaviors associated with chronic nicotine exposure has not been explored. Here, we assessed the effect of chronic nicotine exposure and its subsequent overnight withdrawal on anxiety-like behavior using both quantitative and multivariate T-pattern analysis in rats tested using the hole-board apparatus. Additionally, we explored the role of the LHb by comparing the behavioral effects of short-term nicotine withdrawal in chronically treated LHb-lesioned rats. Quantitative analysis revealed increased anxiety-like behavior in chronically treated overnight nicotine-deprived rats, as manifested in reduced general and focused exploratory behaviors, which was eased in animals that received nicotine. Quantitative analysis failed to reveal a role of the LHb in overnight nicotine deprivation-induced anxiety. Conversely, T-pattern analysis of behavioral outcomes revealed that chronic nicotine-treated rats still show anxiety-like behavior following nicotine challenge. Moreover, it demonstrated that the LHb lesion induced a stronger anxiolytic-like response to the acute challenge of nicotine in chronically nicotine-exposed animals, implicating the LHb in the anxiogenic effect of chronic nicotine exposure. These data further highlight the LHb as a promising target for smoking cessation therapies and support the importance of T-pattern analysis for behavioral analysis.

In vivo endocannabinoid dynamics at the timescale of physiological and pathological neural activity.

The brain's endocannabinoid system is a powerful controller of neurotransmitter release, shaping synaptic communication under physiological and pathological conditions. However, our understanding of endocannabinoid signaling in vivo is limited by the inability to measure their changes at timescales commensurate with the high lability of lipid signals, leaving fundamental questions of whether, how, and which endocannabinoids fluctuate with neural activity unresolved. Using novel imaging approaches in awake behaving mice, we now demonstrate that the endocannabinoid 2-arachidonoylglycerol, not anandamide, is dynamically coupled to hippocampal neural activity with high spatiotemporal specificity. Furthermore, we show that seizures amplify the physiological endocannabinoid increase by orders of magnitude and drive the downstream synthesis of vasoactive prostaglandins that culminate in a prolonged stroke-like event. These results shed new light on normal and pathological endocannabinoid signaling in vivo.

Selective Fatty Acid Amide Hydrolase Inhibitors as Potential Novel Antiepileptic Agents.

Temporal lobe epilepsy is the most common form of epilepsy, and current antiepileptic drugs are ineffective in many patients. The endocannabinoid system has been associated with an on-demand protective response to seizures. Blocking endocannabinoid catabolism would elicit antiepileptic effects, devoid of psychotropic effects. We herein report the discovery of selective anandamide catabolic enzyme fatty acid amide hydrolase (FAAH) inhibitors with promising antiepileptic efficacy, starting from a further investigation of our prototypical inhibitor 2a. When tested in two rodent models of epilepsy, 2a reduced the severity of the pilocarpine-induced status epilepticus and the elongation of the hippocampal maximal dentate activation. Notably, 2a did not affect hippocampal dentate gyrus long-term synaptic plasticity. These data prompted our further endeavor aiming at discovering new antiepileptic agents, developing a new set of FAAH inhibitors (3a-m). Biological studies highlighted 3h and 3m as the best performing analogues to be further investigated. In cell-based studies, using a neuroblastoma cell line, 3h and 3m could reduce the oxinflammation state by decreasing DNA-binding activity of NF-kB p65, devoid of cytotoxic effect. Unwanted cardiac effects were excluded for 3h (Langendorff perfused rat heart). Finally, the new analogue 3h reduced the severity of the pilocarpine-induced status epilepticus as observed for 2a.

In vivo assessment of mechanisms underlying the neurovascular basis of postictal amnesia.

Long-lasting confusion and memory difficulties during the postictal state remain a major unmet problem in epilepsy that lacks pathophysiological explanation and treatment. We previously identified that long-lasting periods of severe postictal hypoperfusion/hypoxia, not seizures per se, are associated with memory impairment after temporal lobe seizures. While this observation suggests a key pathophysiological role for insufficient energy delivery, it is unclear how the networks that underlie episodic memory respond to vascular constraints that ultimately give rise to amnesia. Here, we focused on cellular/network level analyses in the CA1 of hippocampus in vivo to determine if neural activity, network oscillations, synaptic transmission, and/or synaptic plasticity are impaired following kindled seizures. Importantly, the induction of severe postictal hypoperfusion/hypoxia was prevented in animals treated by a COX-2 inhibitor, which experimentally separated seizures from their vascular consequences. We observed complete activation of CA1 pyramidal neurons during brief seizures, followed by a short period of reduced activity and flattening of the local field potential that resolved within minutes. During the postictal state, constituting tens of minutes to hours, we observed no changes in neural activity, network oscillations, and synaptic transmission. However, long-term potentiation of the temporoammonic pathway to CA1 was impaired in the postictal period, but only when severe local hypoxia occurred. Lastly, we tested the ability of rats to perform object-context discrimination, which has been proposed to require temporoammonic input to differentiate between sensory experience and the stored representation of the expected object-context pairing. Deficits in this task following seizures were reversed by COX-2 inhibition, which prevented severe postictal hypoxia. These results support a key role for hypoperfusion/hypoxia in postictal memory impairments and identify that many aspects of hippocampal network function are resilient during severe hypoxia except for long-term synaptic plasticity.

Mycobacterium tuberculosis progresses through two phases of latent infection in humans.

Little is known about the physiology of latent Mycobacterium tuberculosis infection. We studied the mutational rates of 24 index tuberculosis (TB) cases and their latently infected household contacts who developed active TB up to 5.25 years later, as an indication of bacterial physiological state and possible generation times during latent TB infection in humans. Here we report that the rate of new mutations in the M. tuberculosis genome decline dramatically after two years of latent infection (two-sided p < 0.001, assuming an 18 h generation time equal to log phase M. tuberculosis, with latency period modeled as a continuous variable). Alternatively, assuming a fixed mutation rate, the generation time increases over the latency duration. Mutations indicative of oxidative stress do not increase with increasing latency duration suggesting a lack of host or bacterial derived mutational stress. These results suggest that M. tuberculosis enters a quiescent state during latency, decreasing the risk for mutational drug resistance and increasing generation time, but potentially increasing bacterial tolerance to drugs that target actively growing bacteria.