MicroRNA-223 regulates inflammation and brain injury via feedback to NLRP3 inflammasome after intracerebral hemorrhage

NLRP3 inflammasome, the multimeric protein complexes involved in the processing of IL-1β through Caspase-1 cleavage, facilitates the inflammatory response. The control and activation of NLRP3 after intracerebral hemorrhage have not been fully studied. In the current study, we explore the specific microRNA which could regulate the NLRP3 inflammasome and inflammation after intracerebral hemorrhage. We detected the inverse relationship between the expression of miR-223 and NLRP3. We found that NLRP3 mRNA contains conserved miR-223 binding sites in its 3' UTR, and miR-223 could directly regulate NLRP3 expression through these 3' UTR sites. Our results indicate that miR-223 could downregulate NLRP3 to inhibit inflammation through caspase-1 and IL-1β, reduce brain edema and improve neurological functions. Together, miR-223 may be a vital regulator of NLRP3 inflammasome activation. The results suggest that miR-223 represents a novel target reducing the inflammatory response, and offers a new therapeutical strategy following ICH.

Efficacy and Safety of Panax notoginseng Saponin Therapy for Acute Intracerebral Hemorrhage, Meta-Analysis, and Mini Review of Potential Mechanisms of Action

Intracranial/intracerebral hemorrhage (ICH) is a leading cause of death and disability in people with traumatic brain injury (TBI) and stroke. No proven drug is available for ICH. Panax notoginseng (total saponin extraction, PNS) is one of the most valuable herb medicines for stroke and cerebralvascular disorders in China. We searched for randomized controlled clinical trials (RCTs) involving PNS injection to treat cerebral hemorrhage for meta-analysis from various databases including the Chinese Stroke Trials Register, the trials register of the Cochrane Complementary Medicine Field, the Cochrane Central Register of Controlled Trials, MEDLINE, Chinese BioMedical disk, and China Doctorate/Master Dissertations Databases. The quality of the eligible trials was assessed by Jadad’s scale. Twenty (20) of the 24 identified randomized controlled trials matched the inclusive criteria including 984 ICH patients with PNS injection and 907 ICH patients with current treatment (CT). Compared to the CT groups, PNS-treated patients showed better outcomes in the effectiveness rate (ER), neurological deficit score, intracranial hematoma volume, intracerebral edema volume, Barthel index, the number of patients died, and incidence of adverse events. Conclusion: PNS injection is superior to CT for acute ICH. A review of the literature shows that PNS may exert multiple protective mechanisms against ICH-induced brain damage including hemostasis, anti-coagulation, anti-thromboembolism, cerebral vasodilation, invigorated blood dynamics, anti-inflammation, antioxidation, and anti-hyperglycemic effects. Since vitamin C and other brain cell activators (BCA) that are not considered common practice were also used as parts of the CT in several trials, potential PNS and BCA interactions could exist that may have made the effect of PNS therapy less or more impressive than by PNS therapy alone. Future PNS trials with and without the inclusion of such controversial BCAs as part of the CT could clarify the situation. As PNS has a long clinical track record in Asia, it could potentially become a therapy option to treat ICH in the US and Europe. Further clinical trials with better experimental design could determine the long-term effects of PNS treatment for TBI and stroke.

Prestroke glycemic status is associated with the functional outcome in spontaneous intracerebral hemorrhage

Admission hyperglycemia is thought to be related to poor neurological function and high mortality in patients with spontaneous intracerebral hemorrhage (sICH). However, it is not known whether prestroke glycemic status affects functional outcome of sICH. The study was aimed to disclose the association between prestroke glycemic status and outcome in patients with sICH. The study included 288 patients with sICH. Prestroke glycemic status was represented by hemoglobin A1c (HbA1c) values measured the next day after admission. Correlations between HbA1c and age, hematoma volume, NIHSS, and mRS were analyzed using Spearman's correlation analysis. Patients were categorized into two groups according to hematoma volume (≤25 mL or >25 mL), mRS values (≤2 or >2), or hematoma location (lobar hematoma or deep hematoma). Logistic regression analyses were used to determine the relative independent risk factors for hematoma volume, hematoma location, and mRS values. In patients with sICH, HbA1c was significantly correlated with hematoma volume, NIHSS, and mRS. High HbA1c levels were independently associated with large hematoma volume, deep ICH, and poor outcome. When patients were stratified by history of diabetes, the predictive effect of HbA1c on outcomes was only observed in patients with diabetes. Admission glucose was also related to hematoma volume, but failed to predict outcome. Although both admission glucose and HbA1c independently predicted hematoma volume in patients with sICH, HbA1c alone could serve as a better predictor of poor outcome in diabetic patients after sICH.

Hyperbaric oxygen preconditioning attenuates hemorrhagic transformation through increasing PPARγ in hyperglycemic MCAO rats

Hyperbaric oxygen preconditioning (HBO-PC) has been demonstrated to attenuate hemorrhagic transformation (HT) after middle cerebral artery occlusion (MCAO) in hyperglycemic rats. However, the mechanisms remain to be illustrated. Recently, HBO-PC has been shown to activate peroxisome proliferator-activated receptor-gamma (PPARγ) by increasing 15d-PGJ2 in primary cultured neurons. We hypothesize that HBO-PC reduces HT by suppressing inflammation through increasing 15d-PGJ2 and activating PPARγ in hyperglycemic MCAO rats. HBO (2.5ATA) was administered for 1h daily for 5 consecutive days. The PPARγ inhibitor GW9662 was administered intraperitoneally to designated animals. Infarction volume, hemorrhage volume, neurological scores and mortality were analyzed. The levels of 15d-PGJ2, PPARγ, TNF-α and IL-1β, tight junction proteins as well as the activity of MMP-2 and MMP-9 were evaluated 24h after MCAO. HBO-PC reduced HT, improved neurological function, down-regulated inflammatory molecules and inhibited the activation of MMP-9 by increasing 15d-PGJ2 and PPARγ at 24h after MCAO. The results suggested that HBO-PC might be an alternative measure to decrease HT in ischemic stroke.

Delayed coupling to feedback inhibition during a critical period for the integration of adult-born granule cells

Developing granule cells (GCs) of the adult dentate gyrus undergo a critical period of enhanced activity and synaptic plasticity before becoming mature. The impact of developing GCs on the activity of preexisting dentate circuits remains unknown. Here we combine optogenetics, acute slice electrophysiology, and in vivo chemogenetics to activate GCs at different stages of maturation to study the recruitment of local target networks. We show that immature (4-week-old) GCs can efficiently drive distal CA3 targets but poorly activate proximal interneurons responsible for feedback inhibition (FBI). As new GCs transition toward maturity, they reliably recruit GABAergic feedback loops that restrict spiking of neighbor GCs, a mechanism that would promote sparse coding. Such inhibitory loop impinges only weakly in new cohorts of young GCs. A computational model reveals that the delayed coupling of new GCs to FBI could be crucial to achieve a fine-grain representation of novel inputs in the dentate gyrus.

Functional changes in glutamate transporters and astrocyte biophysical properties in a rodent model of focal cortical dysplasia

Cortical dysplasia is associated with intractable epilepsy and developmental delay in young children. Recent work with the rat freeze-induced focal cortical dysplasia (FCD) model has demonstrated that hyperexcitability in the dysplastic cortex is due in part to higher levels of extracellular glutamate. Astrocyte glutamate transporters play a pivotal role in cortical maintaining extracellular glutamate concentrations. Here we examined the function of astrocytic glutamate transporters in a FCD model in rats. Neocortical freeze lesions were made in postnatal day (PN) 1 rat pups and whole cell electrophysiological recordings and biochemical studies were performed at PN 21–28. Synaptically evoked glutamate transporter currents in astrocytes showed a near 10-fold reduction in amplitude compared to sham operated controls. Astrocyte glutamate transporter currents from lesioned animals were also significantly reduced when challenged exogenously applied glutamate. Reduced astrocytic glutamate transport clearance contributed to increased NMDA receptor-mediated current decay kinetics in lesioned animals. The electrophysiological profile of astrocytes in the lesion group was also markedly changed compared to sham operated animals. Control astrocytes demonstrate large-amplitude linear leak currents in response to voltage-steps whereas astrocytes in lesioned animals demonstrated significantly smaller voltage-activated inward and outward currents. Significant decreases in astrocyte resting membrane potential and increases in input resistance were observed in lesioned animals. However, Western blotting, immunohistochemistry and quantitative PCR demonstrated no differences in the expression of the astrocytic glutamate transporter GLT-1 in lesioned animals relative to controls. These data suggest that, in the absence of changes in protein or mRNA expression levels, functional changes in astrocytic glutamate transporters contribute to neuronal hyperexcitability in the FCD model.

The CNS under pathophysiologic attack--examining the role of K₂p channels

Members of the two-pore domain K(+) channel (K2P) family are increasingly recognized as being potential targets for therapeutic drugs and could play a role in the diagnosis and treatment of neurologic disorders. Their broad and diverse expression pattern in pleiotropic cell types, importance in cellular function, unique biophysical properties, and sensitivity toward pathophysiologic parameters represent the basis for their involvement in disorders of the central nervous system (CNS). This review will focus on multiple sclerosis (MS) and stroke, as there is growing evidence for the involvement of K2P channels in these two major CNS disorders. In MS, TASK1-3 channels are expressed on T lymphocytes and are part of a signaling network regulating Ca(2+)- dependent pathways that are mandatory for T cell activation, differentiation, and effector functions. In addition, TASK1 channels are involved in neurodegeneration, resulting in autoimmune attack of CNS cells. On the blood-brain barrier, TREK1 channels regulate immune cell trafficking under autoinflammatory conditions. Cerebral ischemia shares some pathophysiologic similarities with MS, including hypoxia and extracellular acidosis. On a cellular level, K2P channels can have both proapoptotic and antiapoptotic effects, either promoting neurodegeneration or protecting neurons from ischemic cell death. TASK1 and TREK1 channels have a neuroprotective effect on stroke development, whereas TASK2 channels have a detrimental effect on neuronal survival under ischemic conditions. Future research in preclinical models is needed to provide a more detailed understanding of the contribution of K2P channel family members to neurologic disorders, before translation to the clinic is an option.

Diabetes mellitus aggravates hemorrhagic transformation after ischemic stroke via mitochondrial defects leading to endothelial apoptosis

Diabetes is a crucial risk factor for stroke and is associated with increased frequency and poor prognosis. Although endothelial dysfunction is a known contributor of stroke, the underlying mechanisms have not been elucidated. The aim of this study was to elucidate the mechanism by which chronic hyperglycemia may contribute to the worsened prognosis following stroke, especially focusing on mitochondrial alterations. We examined the effect of hyperglycemia on hemorrhagic transformation at 24 hours after middle cerebral artery occlusion (MCAO) in streptozotocin (STZ) -induced diabetic mice. We also examined the effects of high-glucose exposure for 6 days on cell death, mitochondrial functions and morphology in human brain microvascular endothelial cells (HBMVECs) or human endothelial cells derived from induced pluripotent stem cells (iCell endothelial cells). Hyperglycemia aggravated hemorrhagic transformation, but not infarction following stroke. High-glucose exposure increased apoptosis, capase-3 activity, and release of apoptosis inducing factor (AIF) and cytochrome c in HBMVECs as well as affected mitochondrial functions (decreased cell proliferation, ATP contents, mitochondrial membrane potential, and increased matrix metalloproteinase (MMP)-9 activity, but not reactive oxygen species production). Furthermore, morphological aberration of mitochondria was observed in diabetic cells (a great deal of fragmentation, vacuolation, and cristae disruption). A similar phenomena were seen also in iCell endothelial cells. In conclusion, chronic hyperglycemia aggravated hemorrhagic transformation after stroke through mitochondrial dysfunction and morphological alteration, partially via MMP-9 activation, leading to caspase-dependent apoptosis of endothelial cells of diabetic mice. Mitochondria-targeting therapy may be a clinically innovative therapeutic strategy for diabetic complications in the future.

Linolenic acid provides multi-cellular protective effects after photothrombotic cerebral ischemia in rats

Alpha-linolenic acid (LIN) has been shown to provide neuroprotective effects against cerebral ischemia. LIN is a potent activator of TREK-1 channel and LIN-induced neuroprotection disappears in Trek1-/- mice, suggesting that this channel is directly related to the LIN-induced resistance of brain against ischemia. However, the cellular mechanism underlying LIN induced neuroprotective effects after ischemia remains unclear. In this study, using a rat photochemical brain ischemia model, we investigated the effects of LIN on the protein abundance of astrocytic glutamate transporter and AQP4, microglia activation, cell apoptosis and behavioral recovery following ischemia. Administration of LIN rescued the protein abundance of astrocytic glutamate transporter GLT-1, decreased the protein abundance of AQP4 and brain edema, inhibited microglia activation, attenuated cell apoptosis and improved behavioral function recovery. Meanwhile, TREK-1 was widely distributed in the cortex and hippocampus, primarily localized in astrocytes and neurons. LIN could potentiate the TREK-1 mediated astrocytic passive conductance and hyperpolarize the membrane potential. Our results suggest that LIN provides multiple cellular neuroprotective effects in cerebral ischemia. TREK-1 may serve as a promising multi-mechanism therapeutic target for the treatment of stroke.

Regulation of action potential waveforms by axonal GABAA receptors in cortical pyramidal neurons

GABAA receptors distributed in somatodendritic compartments play critical roles in regulating neuronal activities, including spike timing and firing pattern; however, the properties and functions of GABAA receptors at the axon are still poorly understood. By recording from the cut end (bleb) of the main axon trunk of layer -5 pyramidal neurons in prefrontal cortical slices, we found that currents evoked by GABA iontophoresis could be blocked by picrotoxin, indicating the expression of GABAA receptors in axons. Stationary noise analysis revealed that single-channel properties of axonal GABAA receptors were similar to those of somatic receptors. Perforated patch recording with gramicidin revealed that the reversal potential of the GABA response was more negative than the resting membrane potential at the axon trunk, suggesting that GABA may hyperpolarize the axonal membrane potential. Further experiments demonstrated that the activation of axonal GABAA receptors regulated the amplitude and duration of action potentials (APs) and decreased the AP-induced Ca2+ transients at the axon. Together, our results indicate that the waveform of axonal APs and the downstream Ca2+ signals are modulated by axonal GABAA receptors.

Dual patch voltage clamp study of low membrane resistance astrocytes in situ

Whole-cell patch clamp recording has been successfully used in identifying the voltage-dependent gating and conductance properties of ion channels in a variety of cells. However, this powerful technique is of limited value in studying low membrane resistance cells, such as astrocytes in situ, because of the inability to control or accurately measure the real amplitude of command voltages. To facilitate the study of ionic conductances of astrocytes, we have developed a dual patch recording method which permits membrane current and membrane potential to be simultaneously recorded from astrocytes in spite of their extraordinarily low membrane resistance. The utility of this technique is demonstrated by measuring the voltage-dependent activation of the inwardly rectifying K⁺ current abundantly expressed in astrocytes and multiple ionic events associated with astrocytic GABA_A receptor activation. This protocol can be performed routinely in the study of astrocytes. This method will be valuable for identifying and characterizing the individual ion channels that orchestrate the electrical activity of low membrane resistance cells.

Rapid dynamic changes of dendritic inhibition in the dentate gyrus by presynaptic activity patterns

The dentate gyrus (DG) serves as a primary gate to control information transfer from the cortex to the hippocampus. Activation of incoming cortical inputs results in rapid synaptic excitation followed by slow GABA-mediated (GABAergic) synaptic inhibition onto DG granule cells (GCs). GABAergic inhibitory interneurons (INs) in the DG comprise fast-spiking (FS) and non-fast-spiking (non-FS) cells. Anatomical analyses of DG INs reveal that FS cells are soma-targeting INs, whereas non-FS cells are dendrite-targeting INs. These two IN classes are differentially recruited by excitatory inputs and in turn provide exquisite spatiotemporal control over GC activity. Yet, little is known how FS and non-FS cells transform their presynaptic dynamics into varying postsynaptic response amplitudes. Using paired recordings in rat hippocampal slices, we show that inhibition in the DG is dominated by somatic GABAergic inputs during periods of sparse presynaptic activity, whereas dendritic GABAergic inputs are rapidly shifted to powerful and sustained inhibition during periods of intense presynaptic activity. The variant dynamics of dendritic inhibition is dependent on presynaptic IN subtypes and their activity patterns and is attributed to Ca(2+)-dependent increases in the probability of release and the size of the readily releasable pool. Furthermore, the degree of dynamic GABA release can be reduced by blocking voltage-gated K(+) channels, which increases the efficacy of dendrite-targeting IN output synapses during sparse firing. Such rapid dynamic modulation of dendritic inhibition may act as a frequency-dependent filter to prevent overexcitation of GC dendrites and thus set the excitatory-inhibitory synaptic balance in the DG circuits.

A neuroproteomic and systems biology analysis of rat brain post intracerebral hemorrhagic stroke

Intracerebral hemorrhage (ICH) is a devastating form of stroke leading to a high rate of death and disability worldwide. Although it has been hypothesized that much of the IHC insult occurs in the subacute period mediated via a series of complex pathophysiological cascades, the molecular mechanisms involved in ICH have not been systematically characterized. Among the best approaches to understand the underlying mechanisms of injury and recovery, protein dynamics assessment via proteomics/systems biology platforms represent one of the cardinal techniques optimized for mechanisms investigation and biomarker identification. A proteomics approach may provide a biomarker focused framework from which to identify candidate biomarkers of pathophysiological processes involved in brain injury after stroke. In this work, a neuroproteomic approach (LC-MS/MS) was applied to investigate altered expression of proteins that are induced in brain tissue 3 h after injury in a rat model of ICH. Data from sham and focal ischemic models were also obtained and used for comparison. Based on the differentially expressed protein profile, systems biology analysis was conducted to identify associated cellular processes and related interaction maps. After LC-MS/MS analysis of the 3 h brain lysates, 86 proteins were differentially expressed between hemorrhagic and sham tissues. Furthermore, 38 proteins were differentially expressed between ischemic and sham tissues. On the level of global pathway analysis, hemorrhagic stroke proteins were shown to be involved in autophagy, ischemia, necrosis, apoptosis, calpain activation, and cytokine secretion. Moreover, ischemic stroke proteins were related to cell death, ischemia, inflammation, oxidative stress, caspase activation and apoptotic injury. In conclusion, the proteomic responses identified in this study provide key information about target proteins involved in specific pathological pathways.

Synaptic elements for GABAergic feed-forward signaling between HII horizontal cells and blue cone bipolar cells are enriched beneath primate S-cones

The functional roles and synaptic features of horizontal cells in the mammalian retina are still controversial. Evidence exists for feedback signaling from horizontal cells to cones and feed-forward signaling from horizontal cells to bipolar cells, but the details of the latter remain elusive. Here, immunohistochemistry and confocal microscopy were used to analyze the expression patterns of the SNARE protein syntaxin-4, the GABA receptor subunits α1 and ρ, and the cation-chloride cotransporters NKCC and KCC2 in the outer plexiform layer of primate retina. In macaque retina, as observed previously in other species, syntaxin-4 was expressed on dendrites and axon terminals of horizontal cells at cone pedicles and rod spherules. At cones, syntaxin-4 appeared densely clustered in two bands, at horizontal cell dendritic tips and at the level of desmosome-like junctions. Interestingly, in the lower band where horizontal cells may synapse directly onto bipolar cells, syntaxin-4 was highly enriched beneath short-wavelength sensitive (S) cones and colocalized with calbindin, a marker for HII horizontal cells. The enrichment at S-cones was not observed in either mouse or ground squirrel. Furthermore, high amounts of both GABA receptor and cation-chloride cotransporter subunits were found beneath primate S-cones. Finally, while syntaxin-4 was expressed by both HI and HII horizontal cell types, the intense clustering and colocalization with calbindin at S-cones indicated an enhanced expression in HII cells. Taken together, GABA receptors beneath cone pedicles, chloride transporters, and syntaxin-4 are putative constituents of a synaptic set of proteins which would be required for a GABA-mediated feed-forward pathway via horizontal cells carrying signals directly from cones to bipolar cells.

Distinct determinants of sparse activation during granule cell maturation

Adult neurogenesis continually produces a small population of immature granule cells (GCs) within the dentate gyrus. The physiological properties of immature GCs distinguish them from the more numerous mature GCs and potentially enables distinct network functions. To test how the changing properties of developing GCs affect spiking behavior, we examined synaptic responses of mature and immature GCs in hippocampal slices from adult mice. Whereas synaptic inhibition restricted GC spiking at most stages of maturation, the relative influence of inhibition, excitatory synaptic drive, and intrinsic excitability shifted over the course of maturation. Mature GCs received profuse afferent innervation such that spiking was suppressed primarily by inhibition, whereas immature GC spiking was also limited by the strength of excitatory drive. Although the input resistance was a reliable indicator of maturation, it did not determine spiking probability at immature stages. Our results confirm the existence of a transient period during GC maturation when perforant path stimulation can generate a high probability of spiking, but also reveal that immature GC excitability is tempered by functional synaptic inhibition and reduced excitatory innervation, likely maintaining the sparse population activity observed in vivo.

Tonic GABAA conductance decreases membrane time constant and increases EPSP-spike precision in hippocampal pyramidal neurons

Because of a complex dendritic structure, pyramidal neurons have a large membrane surface relative to other cells and so a large electrical capacitance and a large membrane time constant (τ_m). This results in slow depolarizations in response to excitatory synaptic inputs, and consequently increased and variable action potential latencies, which may be computationally undesirable. Tonic activation of GABA_A receptors increases membrane conductance and thus regulates neuronal excitability by shunting inhibition. In addition, tonic increases in membrane conductance decrease the membrane time constant (τ_m), and improve the temporal fidelity of neuronal firing. Here we performed whole-cell current clamp recordings from hippocampal CA1 pyramidal neurons and found that bath application of 10μM GABA indeed decreases τ_m in these cells. GABA also decreased first spike latency and jitter (standard deviation of the latency) produced by current injection of 2 rheobases (500 ms). However, when larger current injections (3–6 rheobases) were used, GABA produced no significant effect on spike jitter, which was low. Using mathematical modeling we demonstrate that the tonic GABA_A conductance decreases rise time, decay time and half-width of EPSPs in pyramidal neurons. A similar effect was observed on EPSP/IPSP pairs produced by stimulation of Schaffer collaterals: the EPSP part of the response became shorter after application of GABA. Consistent with the current injection data, a significant decrease in spike latency and jitter was obtained in cell attached recordings only at near-threshold stimulation (50% success rate, S₅₀). When stimulation was increased to 2- or 3- times S₅₀, GABA significantly affected neither spike latency nor spike jitter. Our results suggest that a decrease in τ_m associated with elevations in ambient GABA can improve EPSP-spike precision at near-threshold synaptic inputs.

The contribution of TWIK-1 channels to astrocyte K(+) current is limited by retention in intracellular compartments

TWIK-1 two-pore domain K⁺ channels are expressed abundantly in astrocytes. In the present study, we examined the extent to which TWIK-1 contributes to the linear current-voltage (I–V) relationship (passive) K⁺ membrane conductance, a dominant electrophysiological feature of mature hippocampal astrocytes. Astrocytes from TWIK-1 knockout mice have a more negative resting potential than those from wild type animals and a reduction in both inward rectification and Cs⁺ permeability. Nevertheless, the overall whole-cell passive conductance is not altered significantly in TWIK-1 knockout astrocytes. The expression of K_ir4.1 and TREK-1, two other major astrocytic K⁺ channels, or of other two-pore K⁺ channels is not altered in TWIK-1 knockout mice, suggesting that the mild effect of TWIK-1 knockout does not result from compensation by these channels. Fractionation experiments showed that TWIK-1 is primarily localized in intracellular cytoplasmic fractions (55%) and mildly hydrophobic internal compartment fractions (41%), with only 5% in fractions containing plasma membranes. Our study revealed that TWIK-1 proteins are mainly located in the intracellular compartments of hippocampal astrocyte under physiological condition, therefore a minimal contribution of TWIK-1 channels to whole-cell currents is likely attributable to a relatively low level presence of channels in the plasma membrane.

Mature teratoma of the petrous bone with extension into the cerebellopontine angle: case report

Purpose Intracranial teratomas in children involving lateral structures such as the petrous portion of the temporal bone are very uncommon. The authors report a case of a petrous teratoma with significant extension into the cerebellopontine angle with brainstem compression.

Case Report An 11-year-old girl presented left-sided facial weakness. Computed tomography (CT) demonstrated a multiloculated lesion expanding the labyrinthine structures in the left petrous temporal bone including the vestibule, semicircular canals, and cochlea, with extension to the left cerebellopontine angle via the expanded left internal auditory canal. The tumor was resected via a transtemporal approach with no evidence of recurrence at nearly 2 years.

Conclusion Complete resection should be the primary treatment for these tumors to minimize the risk of recurrence. To the authors' knowledge, this is the first case report of a mature teratoma originating in the petrous bone with extension into the cerebellopontine angle.

Adult neurogenesis in the mammalian hippocampus: why the dentate gyrus?

In the adult mammalian brain, newly generated neurons are continuously incorporated into two networks: interneurons born in the subventricular zone migrate to the olfactory bulb, whereas the dentate gyrus (DG) of the hippocampus integrates locally born principal neurons. That the rest of the mammalian brain loses significant neurogenic capacity after the perinatal period suggests that unique aspects of the structure and function of DG and olfactory bulb circuits allow them to benefit from the adult generation of neurons. In this review, we consider the distinctive features of the DG that may account for it being able to profit from this singular form of neural plasticity. Approaches to the problem of neurogenesis are grouped as "bottom-up," where the phenotype of adult-born granule cells is contrasted to that of mature developmentally born granule cells, and "top-down," where the impact of altering the amount of neurogenesis on behavior is examined. We end by considering the primary implications of these two approaches and future directions.

Differential central pathology and cognitive impairment in pre-diabetic and diabetic mice

Although age remains the main risk factor to suffer Alzheimer's disease (AD) and vascular dementia (VD), type 2 diabetes (T2D) has turned up as a relevant risk factor for dementia. However, the ultimate underlying mechanisms for this association remain unclear. In the present study we analyzed central nervous system (CNS) morphological and functional consequences of long-term insulin resistance and T2D in db/db mice (leptin receptor KO mice). We also included C57Bl6 mice fed with high fat diet (HFD) and a third group of C57Bl6 streptozotocin (STZ) treated mice. Db/db mice exhibited pathological characteristics that mimic both AD and VD, including age dependent cognitive deterioration, brain atrophy, increased spontaneous hemorrhages and tau phosphorylation, affecting the cortex preferentially. A similar profile was observed in STZ-induced diabetic mice. Moreover metabolic parameters, such as body weight, glucose and insulin levels are good predictors of many of these alterations in db/db mice. In addition, in HFD-induced hyperinsulinemia in C57Bl6 mice, we only observed mild CNS alterations, suggesting that central nervous system dysfunction is associated with well established T2D. Altogether our results suggest that T2D may promote many of the pathological and behavioral alterations observed in dementia, supporting that interventions devoted to control glucose homeostasis could improve dementia progress and prognosis.

Endogenous zinc depresses GABAergic transmission via T-type Ca(2+) channels and broadens the time window for integration of glutamatergic inputs in dentate granule cells

Abstract Zinc actions on synaptic transmission span the modulation of neurotransmitter receptors, transporters, activation of intracellular cascades and alterations in gene expression. Whether and how zinc affects inhibitory synaptic signalling in the dentate gyrus remains largely unexplored. We found that mono- and di-synaptic GABAergic inputs onto dentate granule cells were reversibly depressed by exogenous zinc application and enhanced by zinc chelation. Blocking T-type Ca²⁺ channels prevented the effect of zinc chelation. When recording from dentate fast-spiking interneurones, zinc chelation facilitated T-type Ca²⁺ currents, increased action potential half-width and decreased spike threshold. It also increased the offset of the input–output relation in a manner consistent with enhanced excitability. In granule cells, chelation of zinc reduced the time window for the integration of glutamatergic inputs originating from perforant path synapses, resulting in reduced spike transfer. Thus, zinc-mediated modulation of dentate interneurone excitability and GABA release regulates information flow to local targets and hippocampal networks.

α4βδ GABAA receptors and tonic inhibitory current during adolescence: effects on mood and synaptic plasticity

The onset of puberty is associated with alterations in mood as well as changes in cognitive function, which can be more pronounced in females. Puberty onset in female mice is associated with increased expression of α4βδ γ-amino-butyric acid-A (GABAA) receptors (GABARs) in CA1 hippocampus. These receptors, which normally have low expression in this central nervous system (CNS) site, emerge along the apical dendrites as well as on the dendritic spines of pyramidal neurons, adjacent to excitatory synapses where they underlie a tonic inhibition that shunts excitatory current and impairs activation of N-methyl-D-aspartate (NMDA) receptors, the trigger for synaptic plasticity. As would be expected, α4βδ expression at puberty also prevents long-term potentiation (LTP), an in vitro model of learning which is a function of network activity, induced by theta burst stimulation of the Schaffer collaterals to the CA1 hippocampus. The expression of these receptors also impairs spatial learning in a hippocampal-dependent task. These impairments are not seen in δ knock-out (-/-) mice, implicating α4βδ GABARs. α4βδ GABARs are also a sensitive target for steroids such as THP ([allo]pregnanolone or 3α-OH-5α[β]-pregnan-20-one), which are dependent upon the polarity of GABAergic current. It is well-known that THP can increase depolarizing current gated by α4βδ GABARs, but more recent data suggest that THP can reduce hyperpolarizing current by accelerating receptor desensitization. At puberty, THP reduces the hyperpolarizing GABAergic current, which removes the shunting inhibition that impairs synaptic plasticity and learning at this time. However, THP, a stress steroid, also increases anxiety, via its action at α4βδ GABARs because it is not seen in δ(-/-) mice. These findings will be discussed as well as their relevance to changes in mood and cognition at puberty, which can be a critical period for certain types of learning and when anxiety disorders and mood swings can emerge.

A stress steroid triggers anxiety via increased expression of α4βδ GABAA receptors in methamphetamine dependence

Methamphetamine (METH) is an addictive stimulant drug. In addition to drug craving and lethargy, METH withdrawal is associated with stress-triggered anxiety. However, the cellular basis for this stress-triggered anxiety is not understood. The present results suggest that during METH withdrawal (24h) following chronic exposure (3mg/kg, i.p. for 3-5weeks) of adult, male mice, the effect of one neurosteroid released by stress, 3α,5α-THP (3α-OH-5α-pregnan-20-one), and its 3α,5β isomer reverse to trigger anxiety assessed by the acoustic startle response (ASR), in contrast to their usual anti-anxiety effects. This novel effect of 3α,5β-THP was due to increased (three-fold) hippocampal expression of α4βδ GABAA receptors (GABARs) during METH withdrawal (24h-4weeks) because anxiogenic effects of 3α,5β-THP were not seen in α4-/- mice. 3α,5β-THP reduces current at these receptors when it is hyperpolarizing, as observed during METH withdrawal. As a result, 3α,5β-THP (30nM) increased neuronal excitability, assessed with current clamp and cell-attached recordings in CA1hippocampus, one CNS site which regulates anxiety. α4βδ GABARs were first increased 1h after METH exposure and recovered 6weeks after METH withdrawal. Similar increases in α4βδ GABARs and anxiogenic effects of 3α,5β-THP were noted in rats during METH withdrawal (24h). In contrast, the ASR was increased by chronic METH treatment in the absence of 3α,5β-THP administration due to its stimulant effect. Although α4βδ GABARs were increased by chronic METH treatment, the GABAergic current recorded from hippocampal neurons at this time was a depolarizing, shunting inhibition, which was potentiated by 3α,5β-THP. This steroid reduced neuronal excitability and anxiety during chronic METH treatment, consistent with its typical effect. Flumazenil (10mg/kg, i.p., 3×) reduced α4βδ expression and prevented the anxiogenic effect of 3α,5β-THP after METH withdrawal. Our findings suggest a novel mechanism underlying stress-triggered anxiety after METH withdrawal mediated by α4βδ GABARs.

Ba2+- and bupivacaine-sensitive background K+ conductances mediate rapid EPSP attenuation in oligodendrocyte precursor cells

Glutamatergic transmission onto oligodendrocyte precursor cells (OPCs) may regulate OPC proliferation, migration and differentiation. Dendritic integration of excitatory postsynaptic potentials (EPSPs) is critical for neuronal functions, and mechanisms regulating dendritic propagation and summation of EPSPs are well understood. However, little is known about EPSP attenuation and integration in OPCs. We developed realistic OPC models for synaptic integration, based on passive membrane responses of OPCs obtained by simultaneous dual whole-cell patch-pipette recordings. Compared with neurons, OPCs have a very low value of membrane resistivity, which is largely mediated by Ba(2+)- and bupivacaine-sensitive background K(+) conductances. The very low membrane resistivity not only leads to rapid EPSP attenuation along OPC processes but also sharpens EPSPs and narrows the temporal window for EPSP summation. Thus, background K(+) conductances regulate synaptic responses and integration in OPCs, thereby affecting activity-dependent neuronal control of OPC development and function.

Hyperglycemia exacerbates intracerebral hemorrhage via the downregulation of aquaporin-4: temporal assessment with magnetic resonance imaging

BACKGROUND AND PURPOSE

Intracerebral hemorrhage (ICH) is associated with high mortality and neurological deficits, and concurrent hyperglycemia usually worsens clinical outcomes. Aquaporin-4 (AQP-4) is important in cerebral water movement. Our aim was to investigate the role of AQP-4 in hyperglycemic ICH.

METHODS

Hyperglycemia was induced by intraperitoneal injection of streptozotocin (STZ; 60 mg/kg) in adult Sprague-Dawley male rats. ICH was induced by stereotaxic infusion of collagenase/heparin into the right striatum. One set of rats was repeatedly monitored by MRI at 1, 4, and 7 days after ICH induction so as to acquire information on the formation of hematoma and edema. Another set of rats was killed and brains were examined for differences in the degree of hemorrhage and edema, water content, blood-brain barrier destruction, and AQP-4 expression.

RESULTS

Hyperglycemia ICH rats exhibited increased brain water content, more severe blood-brain barrier destruction, and greater vasogenic edema as seen on diffusion-weighted MRI. Significant downregulation of AQP-4 was observed in STZ-treated rats after ICH as compared with non-STZ-treated rats. Apoptosis was greater on day 1 after ICH in STZ-treated rats.

CONCLUSIONS

The expression of AQP-4 in the brain is downregulated in hyperglycemic rats as compared with normoglycemic rats after ICH. This change is accompanied by increased vasogenic brain edema and more severe blood-brain barrier destruction.

Acid-sensing ion channel-1a is not required for normal hippocampal LTP and spatial memory

Acid-sensing ion channel-1a (ASIC1a) is localized in brain regions with high synaptic density and is thought to contribute to synaptic plasticity, learning, and memory. A prominent hypothesis is that activation of postsynaptic ASICs promotes depolarization, thereby augmenting N-methyl-d-aspartate receptor function and contributing to the induction of long-term potentiation (LTP). However, evidence for activation of postsynaptic ASICs during neurotransmission has not been established. Here, we re-examined the role of ASIC1a in LTP in the hippocampus using pharmacological and genetic approaches. Our results showed that a tarantula peptide psalmotoxin, which profoundly blocked ASIC currents in the hippocampal neurons, had no effect on LTP. Similarly, normal LTP was robustly generated in ASIC1a-null mice. A further behavioral analysis showed that mice lacking ASIC1a had normal performance in hippocampus-dependent spatial memory. In summary, our results indicate that ASIC1a is not required for hippocampal LTP and spatial memory. We therefore propose that the role of ASIC1a in LTP and spatial learning should be reassessed.

Cortical inhibition, pH and cell excitability in epilepsy: what are optimal targets for antiepileptic interventions?

Epilepsy is characterised by the propensity of the brain to generate spontaneous recurrent bursts of excessive neuronal activity, seizures. GABA-mediated inhibition is critical for restraining neuronal excitation in the brain, and therefore potentiation of GABAergic neurotransmission is commonly used to prevent seizures. However, data obtained in animal models of epilepsy and from human epileptic tissue suggest that GABA-mediated signalling contributes to interictal and ictal activity. Prolonged activation of GABA(A) receptors during epileptiform bursts may even initiate a shift in GABAergic neurotransmission from inhibitory to excitatory and so have a proconvulsant action. Direct targeting of the membrane mechanisms that reduce spiking in glutamatergic neurons may better control neuronal excitability in epileptic tissue. Manipulation of brain pH may be a promising approach and recent advances in gene therapy and optogenetics seem likely to provide further routes to effective therapeutic intervention.

Dynamic functions of GABA signaling during granule cell maturation

The dentate gyrus is one of the few areas of the brain where new neurons are generated throughout life. Neural activity influences multiple stages of neurogenesis, thereby allowing experience to regulate the production of new neurons. It is now well established that GABA_A receptor-mediated signaling plays a pivotal role in mediating activity-dependent regulation of adult neurogenesis. GABA first acts as a trophic signal that depolarizes progenitors and early post mitotic granule cells, enabling network activity to control molecular cascades essential for proliferation, survival and growth. Following the development of glutamatergic synaptic inputs, GABA signaling switches from excitatory to inhibitory. Thereafter robust synaptic inhibition enforces low spiking probability of granule cells in response to cortical excitatory inputs and maintains the sparse activity patterns characteristic of this brain region. Here we review these dynamic functions of GABA across granule cell maturation, focusing on the potential role of specific interneuron circuits at progressive developmental stages. We further highlight questions that remain unanswered about GABA signaling in granule cell development and excitability.

Small RNA interference-mediated gene silencing of TREK-1 potassium channel in cultured astrocytes

This study was aimed to examine the effect of TREK-1 silencing on the function of astrocytes. Three 21-nucleotide small interfering RNA (siRNA) duplexes (siT1, siT2, siT3) targeting TREK-1 were constructed. Cy3-labeled dsRNA oligmers were used to determine the transfection efficiency in cultured astrocytes. TREK-1-specific siRNA duplexes (siT1, siT2, siT3) at the optimal concentration were transfected into cultured astrocytes, and the most efficient siRNA was identified by the method of immunocytochemical staining and Western blotting. The proliferation of astrocytes tranfected with TREK-1-targeting siRNA under hypoxia condition was measured by fluorescence-activated cell sorting (FACS). The results showed that TREK-1 was expressed in cultured astrocytes. The dsRNA oligmers targeting TREK-1 could be transfected efficiently in cultured astrocytes and down-regulate the expression of TREK-1 in astrocytes. Moreover, the down-regulation of TREK-1 in astrocytes contributed to the proliferation of astrocytes under hypoxia condition as determined by cell cycle analysis. It was concluded that siRNA is a powerful technique that can be used to knockdown the expression of TREK-1 in astrocytes, which helps further investigate the function of TREK-1 channel in astrocytes under physicological and pathological condition.

Application of proteomics to cerebrovascular disease

While neurovascular diseases such as ischemic and hemorrhagic stroke are the leading causes of disability in the world, the repertoire of therapeutic interventions has remained remarkably limited. There is a dire need to develop new diagnostic, prognostic, and therapeutic options. The study of proteomics is particularly enticing for cerebrovascular diseases such as stroke, which most likely involve multiple gene interactions resulting in a wide range of clinical phenotypes. Currently, rapidly progressing neuroproteomic techniques have been employed in clinical and translational research to help identify biologically relevant pathways, to understand cerebrovascular pathophysiology, and to develop novel therapeutics and diagnostics. Future integration of proteomic with genomic, transcriptomic, and metabolomic studies will add new perspectives to better understand the complexities of neurovascular injury. Here, we review cerebrovascular proteomics research in both preclinical (animal, cell culture) and clinical (blood, urine, cerebrospinal fluid, microdialyates, tissue) studies. We will also discuss the rewards, challenges, and future directions for the application of proteomics technology to the study of various disease phenotypes. To capture the dynamic range of cerebrovascular injury and repair with a translational targeted and discovery approach, we emphasize the importance of complementing innovative proteomic technology with existing molecular biology models in preclinical studies, and the need to advance pharmacoproteomics to directly probe clinical physiology and gauge therapeutic efficacy at the bedside.

Short-term ionic plasticity at GABAergic synapses

Fast synaptic inhibition in the brain is mediated by the pre-synaptic release of the neurotransmitter γ-Aminobutyric acid (GABA)and the post-synaptic activation of GABA-sensitive ionotropic receptors. As with excitatory synapses, it is being increasinly appreciated that a variety of plastic processes occur at inhibitory synapses, which operate over a range of timescales. Here we examine a form of activity-dependent plasticity that is somewhat unique to GABAergic transmission. This involves short-lasting changes to the ionic driving force for the post-synaptic receptors, a process referred to as short-term ionic plasticity. These changes are directly related to the history of activity at inhibitory synapses and are influenced by a variety of factors including the location of the synapse and the post-synaptic cell's ion regulation mechanisms. We explore the processes underlying this form of plasticity, when and where it can occur, and how it is likely to impact network activity.

Refuting the challenges of the developmental shift of polarity of GABA actions: GABA more exciting than ever!

During brain development, there is a progressive reduction of intracellular chloride associated with a shift in GABA polarity: GABA depolarizes and occasionally excites immature neurons, subsequently hyperpolarizing them at later stages of development. This sequence, which has been observed in a wide range of animal species, brain structures and preparations, is thought to play an important role in activity-dependent formation and modulation of functional circuits. This sequence has also been considerably reinforced recently with new data pointing to an evolutionary preserved rule. In a recent “Hypothesis and Theory Article,” the excitatory action of GABA in early brain development is suggested to be “an experimental artefact” (Bregestovski and Bernard, 2012). The authors suggest that the excitatory action of GABA is due to an inadequate/insufficient energy supply in glucose-perfused slices and/or to the damage produced by the slicing procedure. However, these observations have been repeatedly contradicted by many groups and are inconsistent with a large body of evidence including the fact that the developmental shift is neither restricted to slices nor to rodents. We summarize the overwhelming evidence in support of both excitatory GABA during development, and the implications this has in developmental neurobiology.

GABAergic synaptic transmission triggers action potentials in thalamic reticular nucleus neurons

GABAergic neurons in the thalamic reticular nucleus (TRN) form powerful inhibitory connections with several dorsal thalamic nuclei, thereby controlling attention, sensory processing, and synchronous oscillations in the thalamocortical system. TRN neurons are interconnected by a network of GABAergic synapses, but their properties and their role in shaping TRN neuronal activity are not well understood. Using recording techniques aimed to minimize changes in the intracellular milieu, we show that synaptic GABA(A) receptor activation triggers postsynaptic depolarizations in mouse TRN neurons. Immunohistochemical data indicate that TRN neurons express very low levels of the Cl(-) transporter KCC2. In agreement, perforated-patch recordings show that intracellular Cl(-) levels are high in TRN neurons, resulting in a Cl(-) reversal potential (E(Cl)) significantly depolarized from rest. Additionally, we find that GABA(A) receptor-evoked depolarizations are amplified by the activation of postsynaptic T-type Ca(2+) channels, leading to dendritic Ca(2+) increases and the generation of burst firing in TRN neurons. In turn, GABA-evoked burst firing results in delayed and long-lasting feedforward inhibition in thalamic relay cells. Our results show that GABA-evoked depolarizations can interact with T-type Ca(2+) channels to powerfully control spike generation in TRN neurons.

Mature cystic teratoma (dermoid cyst) in the sylvian fissure: a case report and review of the literature

Mature cystic teratoma (dermoid cyst) inside the Sylvian fissure is rare. A 14-year-old boy presented with 2 episodes of generalized tonic-clonic seizures. Using a fat-suppressed, T1-weighted sequence, magnetic resonance imaging revealed a hypointense nonenhancing mass in the left Sylvian fissure. He underwent left pterional craniotomy for total tumor resection. The pathological diagnosis was mature cystic teratoma (dermoid cyst). Headache and seizures are the leading symptoms. Cyst rupture causes inflammation of cholesterol crystals, and the cyst contents may cause seizure. Surgical resection is the treatment of choice, but radical resection is not advised if critical neurovascular structure can be injured.

Isoflurane preconditioning protects astrocytes from oxygen and glucose deprivation independent of innate cell sex

BACKGROUND

Isoflurane exposure can protect the mammalian brain from subsequent insults such as ischemic stroke. However, this protective preconditioning effect is sexually dimorphic, with isoflurane preconditioning decreasing male while exacerbating female brain damage in a mouse model of cerebral ischemia. Emerging evidence suggests that innate cell sex is an important factor in cell death, with brain cells having sex-specific sensitivities to different insults. We used an in vitro model of isoflurane preconditioning and ischemia to test the hypothesis that isoflurane preconditioning protects male astrocytes while having no effect or even a deleterious effect in female astrocytes after subsequent oxygen and glucose deprivation (OGD).

METHODS

Sex-segregated astrocyte cultures derived from postnatal day 0 to 1 mice were allowed to reach confluency before being exposed to either 0% (sham preconditioning) or 3% isoflurane preconditioning for 2 hours. Cultures were then returned to normal growth conditions for 22 hours before undergoing 10 hours of OGD. Twenty-four hours after OGD, cell viability was quantified using a lactate dehydrogenase assay.

RESULTS

Isoflurane preconditioning increased cell survival after OGD compared with sham preconditioning independent of innate cell sex.

CONCLUSION

More studies are needed to determine how cell type and cell sex may impact on anesthetic preconditioning and subsequent ischemic outcomes in the brain.

Investigation of the effect of hyperglycemia on intracerebral hemorrhage by proteomic approaches

Intracerebral hemorrhage (ICH) is associated with high mortality and disability, and hyperglycemia worsens the clinical and neurological outcomes of patients with ICH. In this study, we utilized proteomic approaches to investigate the role of hyperglycemia in ICH. Hyperglycemia was induced by intraperitoneal injection of streptozotocin (STZ) in adult Sprague-Dawley male rats; ICH was induced by stereotaxic infusion of collagenase/heparin into the right striatum. It was observed that the size of induced hemorrhage was significantly larger in the hyperglycemic group (n=6 in each group). On the first day after ICH, an apparent decrease in the bilateral grasp was also observed for the lesioned hyperglycemic rats compared with normoglycemic ones. When employing 2-DE and MS to examine the proteomes of perihematomal and control regions in individual hyperglycemic and normoglycemic rats, eight differentially expressed protein targets were identified. Most noteworthy, in response to ICH significant increase of albumin was ubiquitously observed in the brains of normoglycemic rats but not in the brains of hyperglycemic rats. Coincidentally, more significant neuronal apoptosis were found in the perihematomal regions of hyperglycemic rats. These observations described suggest the protection role of albumin in acute stage of ICH, which may be dependent on different blood sugar levels.

Mature posterior fossa teratoma mimicking infratentorial meningioma: a case report

Intracranial teratomas are congenital neoplasms mostly diagnosed in the pediatric hood and usually involve supratentorial midline structures. These teratomas, especially those involving the posterior fossa are an uncommon and representing less than 0.5% of all intracranial tumors. We report a case of mature posterior fossa teratoma in an adult patient diagnosed in the 4th decade of life. This lesion was taken for a huge infratentorial meningioma.

Changes in lipid-sensitive two-pore domain potassium channel TREK-1 expression and its involvement in astrogliosis following cerebral ischemia in rats

Astrocytes play an active and important role in the pathophysiology of cerebral ischemia. We have previously shown that mature hipppocampal astrocytes functionally express two-pore domain K(+) channel TREK-1, which significantly contributes to the passive conductance and help to set the negative resting membrane potential essential for the optimal operation of some astrocytic homeostatic functions. However, its expression under ischemic conditions remains to be determined. In this study, we examined the expression of TREK-1 in rat brain under physiological and focal ischemia conditions. The results show that TREK-1 was broadly expressed on astrocytes and neurons in the cortex, CA1 region of hippocampus. After middle cerebral artery occlusion induced focal ischemia, the TREK-1 expression was significantly increased at days 3, 7 and 30 following reperfusion, which correlated with reactive astrogliosis in the cortex and hippocampus. Cultured cortical astrocytes also express TREK-1. TREK-1 inhibitor quinine inhibited the proliferation of astrocytes exposed to hypoxia condition. These data provide evidence showing the astrocytic TREK-1 involvement in ischemia pathology.

High-density expression of Ca2+-permeable ASIC1a channels in NG2 glia of rat hippocampus

NG2 cells, a fourth type of glial cell in the mammalian CNS, undergo reactive changes in response to a wide variety of brain insults. Recent studies have demonstrated that neuronally expressed acid-sensing ion channels (ASICs) are implicated in various neurological disorders including brain ischemia and seizures. Acidosis is a common feature of acute neurological conditions. It is postulated that a drop in pH may be the link between the pathological process and activation of NG2 cells. Such postulate immediately prompts the following questions: Do NG2 cells express ASICs? If so, what are their functional properties and subunit composition? Here, using a combination of electrophysiology, Ca2+ imaging and immunocytochemistry, we present evidence to demonstrate that NG2 cells of the rat hippocampus express high density of Ca2+-permeable ASIC1a channels compared with several types of hippocampal neurons. First, nucleated patch recordings from NG2 cells revealed high density of proton-activated currents. The magnitude of proton-activated current was pH dependent, with a pH for half-maximal activation of 6.3. Second, the current-voltage relationship showed a reversal close to the equilibrium potential for Na+. Third, psalmotoxin 1, a blocker specific for the ASIC1a channel, largely inhibited proton-activated currents. Fourth, Ca2+ imaging showed that activation of proton-activated channels led to an increase of [Ca2+]i. Finally, immunocytochemistry showed co-localization of ASIC1a and NG2 proteins in the hippocampus. Thus the acid chemosensor, the ASIC1a channel, may serve for inducing membrane depolarization and Ca2+ influx, thereby playing a crucial role in the NG2 cell response to injury following ischemia.

Intracranial growing teratoma syndrome following radiotherapy--an unusually fulminant course

INTRODUCTION

Residual radiologically progressive masses following multimodality treatment of malignant mixed intracranial germ cell tumors are described. Often these enlarge, and this is called the growing teratoma syndrome. A similar phenomenon during radiotherapy alone has not been described.

SUBJECTS AND METHODS

A 5-year old boy presented with features of raised intracranial pressure. Imaging revealed a posterior third ventricular mass, which was biopsied endoscopically.

RESULTS

A review of the scanty tissue was suggestive of a pineal parenchymal tumor, and hence radiation was planned. After just ten fractions, he developed rapid neurological deterioration. Repeat imaging raised a possibility of a teratomatous tumor. He underwent emergency excision. However, he had a stormy postoperative course and succumbed to deep venous infarction. Histology revealed a purely mature teratoma.

CONCLUSION

Though a growing teratoma syndrome has been described following chemotherapy, no such report while on radiation exists. Ours could be the first such reported case. We discuss the possible mechanisms with a review of the literature.

Intracranial teratomas in children: the role and timing of surgical removal

OBJECT

In this study, the authors report their experience with the surgical treatment of intracranial teratomas with an emphasis on the indications for delayed resection after oncological treatment.

METHODS

The authors retrospectively reviewed the cases of 14 children with intracranial teratomas. The mean age at diagnosis was 10.5 years (range 2 days-18 years), and 11 patients were male. The final histological analysis revealed pure mature teratoma in 5 cases, mixed teratoma with germinoma in 3 cases, and nongerminomatous malignant germ cell tumor in 6 cases. Thirteen patients underwent tumor resection, and these patients were divided into 2 subgroups according to the timing of surgery. In Group A, 10 patients underwent resection as the primary treatment because no tumor markers were detected in 4 patients, a teratomatous component was revealed on biopsy sampling in 3 patients, and a large tumor volume in 3 patients. In Group B, 3 patients underwent removal of residual pure mature teratoma after oncological treatment.

RESULTS

Seven of the 8 patients (87.5%) with pure mature teratomas or with mixed teratoma and germinoma are currently alive (mean follow-up of 9 years); the eighth patient died of postoperative meningitis. Two of the 6 patients (33%) with mixed nongerminomatous malignant germ cell tumors died of tumor progression regardless of the timing of surgery.

CONCLUSIONS

The results of this study support the belief that microsurgical removal is the only effective treatment for intracranial teratomas. Surgery may be performed as the primary therapy when there is evidence of a noninvasive teratoma, and as a secondary therapy if there is only a partial response to neoadjuvant therapy or if progression is observed in mixed malignant germ cell tumors.