Synaptic pruning of murine adult-born neurons by microglia depends on phosphatidylserine.

New neurons, continuously added in the adult olfactory bulb (OB) and hippocampus, are involved in information processing in neural circuits. Here, we show that synaptic pruning of adult-born neurons by microglia depends on phosphatidylserine (PS), whose exposure on dendritic spines is inversely correlated with their input activity. To study the role of PS in spine pruning by microglia in vivo, we developed an inducible transgenic mouse line, in which the exposed PS is masked by a dominant-negative form of milk fat globule-EGF-factor 8 (MFG-E8), MFG-E8D89E.

Visually cued fear conditioning test for memory impairment related to cortical function.

Aim: Fear conditioning tests are intended to elucidate a subject's ability to associate a conditioned stimulus with an aversive, unconditioned stimulus, such as footshock. Among these tests, a paradigm related to precise cortical functions would be increasingly important in drug screening for disorders such as schizophrenia and dementia. Therefore, we established a new fear conditioning paradigm using a visual cue in mice.

A link between vascular damage and cognitive deficits after whole-brain radiation therapy for cancer: A clue to other types of dementia?

Whole brain radiation therapy for the treatment of tumors can sometimes cause cognitive impairment. Memory deficits were noted in up to 50% of treated patients over a short period of several months. In addition, an increased rate of dementia in young patients has been noted over the longer term, i.

Angiogenesis in refractory depression: A possible phenotypic target to avoid the blood brain barrier.

Major depressive syndrome (so-called depression) is a common but serious mental disease that causes low mood. Most patients are treatable, mainly because of high response rates for medicines such as selective serotonin-reuptake inhibitors (SSRIs). However, there are still a considerable number of patients with refractory or drug-resistant depression.

17α-estradiol is generated locally in the male rat brain and can regulate GAD65 expression and anxiety.

Increasing evidence suggests that 17β-estradiol, a sex hormone, is synthesized by neurons. In addition, 17α-estradiol, the stereoisomer of 17β-estradiol, is reported to be the dominant form in the male mouse brain. However, probably because the method to detect these isomers requires unusual and precise experimental design, the presence of this endogenous 17α-estradiol has not been reported subsequently and the actual role is therefore not well elucidated.

Postsynaptic spiking homeostatically induces cell-autonomous regulation of inhibitory inputs via retrograde signaling.

Developing neural circuits face the dual challenge of growing in an activity-induced fashion and maintaining stability through homeostatic mechanisms. Compared to our understanding of homeostatic regulation of excitatory synapses, relatively little is known about the mechanism mediating homeostatic plasticity of inhibitory synapses, especially that following activity elevation. Here, we found that elevating neuronal activity in cultured hippocampal neurons for 4 h significantly increased the frequency and amplitude of mIPSCs, before detectable change at excitatory synapses.

Activity-dependent localization in spines of the F-actin capping protein CapZ screened in a rat model of dementia.

Actin reorganization in dendritic spines is hypothesized to underlie neuronal plasticity. Actin-related proteins, therefore, might serve as useful markers of plastic changes in dendritic spines. Here, we utilized memory deficits induced by fimbria-fornix transection (FFT) in rats as a dementia model to screen candidate memory-associated molecules by using a two-dimensional gel method.

Experience-dependent, rapid structural changes in hippocampal pyramidal cell spines.

Morphological changes in dendritic spines may contribute to the fine tuning of neural network connectivity. The relationship between spine morphology and experience-dependent neuronal activity, however, is largely unknown. In the present study, we combined 2 histological analyses to examine this relationship: 1) Measurement of spines of neurons whose morphology was visualized in brain sections of mice expressing membrane-targeted green fluorescent protein (Thy1-mGFP mice) and 2) Categorization of CA1 neurons by immunohistochemical monitoring of Arc expression as a putative marker of recent neuronal activity.

Influence of brain-derived neurotrophic factor on pathfinding of dentate granule cell axons, the hippocampal mossy fibers.

Mossy fibers, the dentate granule cell axons, are generated throughout an animal's lifetime. Mossy fiber paths and synapses are primarily restricted to the stratum lucidum within the CA3 region. Brain-derived neurotrophic factor (BDNF), a neurotrophin family protein that activates Trk neurotrophin receptors, is highly expressed in the stratum lucidum in an activity-dependent manner.

A novel chalcone polyphenol inhibits the deacetylase activity of SIRT1 and cell growth in HEK293T cells.

SIRT1 is one of seven mammalian orthologs of yeast silent information regulator 2 (Sir2), and it functions as a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase. Recently, resveratrol and its analogues, which are polyphenols, have been reported to activate the deacetylase activity of SIRT1 in an in vitro assay and to expand the life-span of several species through Sir2 and the orthologs. To find activators or inhibitors to SIRT1, we examined thirty-six polyphenols, including stilbenes, chalcones, flavanones, and flavonols, with the SIRT1 deacetylase activity assay using the acetylated peptide of p53 as a substrate.

Imaging mass spectrometry technology and application on ganglioside study; visualization of age-dependent accumulation of C20-ganglioside molecular species in the mouse hippocampus.

Gangliosides are particularly abundant in the central nervous system (CNS) and thought to play important roles in memory formation, neuritogenesis, synaptic transmission, and other neural functions. Although several molecular species of gangliosides have been characterized and their individual functions elucidated, their differential distribution in the CNS are not well understood. In particular, whether the different molecular species show different distribution patterns in the brain remains unclear.

Enhancement of Trk signaling pathways by the cholestane amide conjugate MCC-257.

The cholestane amide conjugate MCC-257 has been shown to augment the effects of nerve growth factor (NGF) on cell survival and on tyrosine phosphorylation of the TrkA receptor in PC12 cells. Recent findings suggest that signaling pathways downstream of Trk are regulated independently. We describe here our finding that the NGF-induced phosphorylation of both ERK and Akt are accelerated by MCC-257.

Contextual learning induces an increase in the number of hippocampal CA1 neurons expressing high levels of BDNF.

We examined behaviorally induced expression of brain-derived neurotrophic factor (BDNF) in area CA1 of the hippocampus. Sprague-Dawley rats were trained in a contextual fear conditioning (CFC) task, sacrificed 4h later, and their brains were processed for immunohistochemistry. We found distinctively high levels of BDNF immunoreactivity in a small number ( approximately 1%) of CA1 neurons in untrained animals.

A low-cost method for brain slice cultures.

Low-cost, simple procedures for organotypic tissue cultures are desirable for high-throughput biological experiments such as large-scale medical/drug screening. We present a practical and economical method to cultivate brain slices using hydrophilic filtration membranes. With a cost reduction of more than 90%, this technique allows us to prepare hippocampal slice cultures that are morphologically and functionally indistinguishable from those obtained by the widely used Millicell-CM method.

Conserved role of brain-derived neurotrophic factor in Val66Met: target-selective reinforcement of GABAergic synapses.

Brain-derived neurotrophic factor has been implicated in higher cognitive functions, and several neurological and psychiatric disorders. Recently, a variant brain-derived neurotrophic factor (BDNFMet), having a substitution referred to as Val66Met, was reported as a product of a bdnf allele with a common single nucleotide polymorphism. It has been reported that BDNFMet is impaired in its potential for activity-dependent release.

Estrogen produced in cultured hippocampal neurons is a functional regulator of a GABAergic machinery.

Accumulating evidence suggests that estrogen is produced locally by the neurons in the brain. We observed that a 48-hr treatment with the estrogen receptor antagonists ICI 182780 and tamoxifen decreased the level of glutamate decarboxylase (GAD)-65, a rate-limiting gamma-aminobutyric acid (GABA)-synthesizing enzyme, in a dissociated hippocampal neuronal culture. Aromatase is an essential enzyme for estrogen biosynthesis.

K252a, an inhibitor of Trk, disturbs pathfinding of hippocampal mossy fibers.

Hippocampal mossy fibers, which are the axons of dentate granule cells, are continuously generated owing to adult neurogenesis of granule cells. They extend exclusively into the stratum lucidum, a proximal layer of the CA3 pyramidal cells. We visualized the mossy fiber tracts by Timm histochemical staining and DiI labeling in the cultured hippocampal slices from newborn rats.

IP3 receptor types 2 and 3 mediate exocrine secretion underlying energy metabolism.

Type 2 and type 3 inositol 1,4,5-trisphosphate receptors (IP3R2 and IP3R3) are intracellular calcium-release channels whose physiological roles are unknown. We show exocrine dysfunction in IP3R2 and IP3R3 double knock-out mice, which caused difficulties in nutrient digestion. Severely impaired calcium signaling in acinar cells of the salivary glands and the pancreas in the double mutants ascribed the secretion deficits to a lack of intracellular calcium release.

Brain-derived neurotrophic factor induces hyperexcitable reentrant circuits in the dentate gyrus.

Aberrant sprouting and synaptic reorganization of the mossy fiber (MF) axons are commonly found in the hippocampus of temporal lobe epilepsy patients and result in the formation of excitatory feedback loops in the dentate gyrus, a putative cellular basis for recurrent epileptic seizures. Using ex vivo hippocampal cultures, we show that prolonged hyperactivity induces MF sprouting and the resultant network reorganizations and that brain-derived neurotrophic factor (BDNF) is necessary and sufficient to evoke these pathogenic plasticities. Hyperexcitation induced an upregulation of BDNF protein expression in the MF pathway, an effect mediated by L-type Ca2+ channels.

BDNF locally potentiates GABAergic presynaptic machineries: target-selective circuit inhibition.

Inhibitory neurotransmission is critical for neuronal circuit formation. To examine whether inhibitory neurotransmission receives target-selective modulation in the long term, we expressed the cDNA of brain-derived neurotrophic factor (BDNF), which has been shown to induce the augmentation of GABAergic synapses in vivo and in vitro, in a small population of cultured hippocampal neurons. At 48 h after transfection, the expression level of glutamic acid decarboxylase 65 (GAD65), a GABA synthetic enzyme that resides mainly in GABAergic terminals, was selectively enhanced around the BDNF-expressing neurons, in comparison with the neighboring control neurons interposed between the BDNF-expressing neurons and inhibitory neurons.

Environmental control of the survival and differentiation of dentate granule neurons.

Dentate granule cells (DGCs) and their microcircuits have been implicated in hippocampus-dependent memory encoding and epileptogenesis. Little is known about how the proper maturation of DGCs is determined by their intrinsic programs or external factors during development. In order to explore this, we dispersed premature DGCs on living hippocampal slices.

BDNF boosts spike fidelity in chaotic neural oscillations.

Oscillatory activity and its nonlinear dynamics are of fundamental importance for information processing in the central nervous system. Here we show that in aperiodic oscillations, brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, enhances the accuracy of action potentials in terms of spike reliability and temporal precision. Cultured hippocampal neurons displayed irregular oscillations of membrane potential in response to sinusoidal 20-Hz somatic current injection, yielding wobbly orbits in the phase space, i.

Developmental switch in axon guidance modes of hippocampal mossy fibers in vitro.

Hippocampal mossy fibers (MFs), axons of dentate granule cells, run through a narrow strip, called the stratum lucidum, and make synaptic contacts with CA3 pyramidal cells. This stereotyped pathfinding is assumed to require a tightly controlled guidance system, but the responsible mechanisms have not been proven directly. To clarify the cellular basis for the MF pathfinding, microslices of the dentate gyrus (DG) and Ammon's horn (AH) were topographically arranged in an organotypic explant coculture system.

Beta-amyloid prevents excitotoxicity via recruitment of glial glutamate transporters.

Amyloid beta-protein (Abeta), a putative pathogenic endotoxin involved in Alzheimer's disease, induces redistribution of glutamate transporters in astrocytes and promotes their pump activity. Because the transporters are assumed to protect neurons against excitotoxicity by removing extracellular glutamate, we hypothesized that Abeta alters the vulnerability of neurons to glutamate. Cerebrocortical neuron-astroglial co-cultures were exposed to glutamate, the concentration of which was selected so that only 20% of the neurons exhibited degeneration.