Ephrin-A5 and EphA5 interaction induces synaptogenesis during early hippocampal development.

Background: Synaptogenesis is a fundamental step in neuronal development. For spiny glutamatergic synapses in hippocampus and cortex, synaptogenesis involves adhesion of pre and postsynaptic membranes, delivery and anchorage of pre and postsynaptic structures including scaffolds such as PSD-95 and NMDA and AMPA receptors, which are glutamate-gated ion channels, as well as the morphological maturation of spines. Although electrical activity-dependent mechanisms are established regulators of these processes, the mechanisms that function during early development, prior to the onset of electrical activity, are unclear.

A new approach for therapeutic use by RNA interference in the brain.

RNA interference (RNAi) is a gene silencing phenomenon that is induced by ribonucleoprotein complexes containing 21-28 nucleotides (nt) of double-stranded RNA (si/miRNA). Although this phenomenon occurs in an inherent manner, it can also be induced in an artificially manipulated manner. Recently, the understanding of RNAi mechanisms has progressed from that in plants to that in mammals.

Activity regulates the expression of AMPA receptor subunit GluR4 in developing visual cortex.

In the developing visual cortex, the expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunit GluR4 precedes that of the other AMPAR subunits GluR1-3, and then declines to become almost absent in adults. The current study shows that the neuronal activity regulates the expression of GluR4 by a culture system in vitro and a dark-rearing (DR) system in vivo. Membrane depolarization by treatment of cultured neurons of the visual cortex with a high concentration of KCl (35 mm; HK) promoted a decline in the expression of GluR4.

Chronic membrane depolarization-induced morphological alteration of developing neurons.

During development of CNS, young neurons experience various stimuli, and thereafter differentiate to mature neurons in an activity-dependent manner. Membrane depolarization acts as an inducer of excitability and various signals in the neurons, which can be used as a model of neuronal activity. However, the mechanisms of the influence of membrane depolarization on neuronal differentiation have not been fully understood.

The remarkable mechanism of prostaglandin E2 on synaptic plasticity.

Prostanoids have a broad spectrum of biological activities in a variety of organs including the brain. However, their effects on synaptic plasticity in the brain, which have been recently revealed, are ambiguous in comparison to those in the other organs. Prostaglandin E(2) (PGE(2)) is a prostanoid produced from arachidonic acid in the cellular membrane, and knowledge about its functions is increasing.

Bidirectional trafficking of prostaglandin E2 receptors involved in long-term potentiation in visual cortex.

Although prostaglandin E2 (PGE2) has a broad spectrum of biological activities that have been confirmed by previous studies, the roles of PGE2 in synaptic plasticity such as long-term potentiation (LTP) in the CNS have yet to be characterized in detail. The present results of electrophysiological and biochemical studies indicated that PGE2 is actually produced in acute visual cortex slices in response to theta-burst stimulation (TBS) and is involved postsynaptically in TBS-induced LTP. RNA interference (RNAi) for PGE2 receptor subtypes EP2 and EP3, which are known to upregulate and downregulate the level of cAMP, respectively, induced significant decreases and increases of LTP, respectively.

RNAi-induced gene silencing by local electroporation in targeting brain region.

Genetic manipulation for "knockout" (KO) is a useful tool for characterizing a target gene. However, its shortcomings that need to be overcome hinder its easy and ready usage in ordinary laboratories. Here we describe a knockdown technique termed the RNA interference (RNAi)-induced gene silencing by local electroporation (RISLE).

Long-term depression is not induced by low-frequency stimulation in rat visual cortex in vivo: a possible preventing role of endogenous brain-derived neurotrophic factor.

Low-frequency stimulation (LFS) at 1 Hz for 15 min is an effective protocol to induce homosynaptic long-term depression (LTD) in visual cortical slices. It is reported that LFS becomes ineffective when brain-derived neurotrophic factor (BDNF) is applied to slices. It is not known, however, whether such a protocol induces LTD in visual cortex in vivo, and whether endogenous BDNF has the same or similar action.

Low-frequency depression of synaptic responses recorded from rat visual cortex.

To characterize the low-frequency depression (LFD) of synaptic transmission in the visual cortex, we recorded field potentials and minimal excitatory postsynaptic potentials (EPSPs) from layer II/III following intracortical stimulation at various frequencies in cortical slices of rats. Field potentials were stable at 0.017 Hz, but showed an amplitude depression at 0.

Brain-derived neurotrophic factor induces long-lasting potentiation of synaptic transmission in visual cortex in vivo in young rats, but not in the adult.

Brain-derived neurotrophic factor (BDNF) rapidly enhances excitatory synaptic transmission in cortical slices. To date, however, a question of how long such an action persists remains unanswered as it is hard to record synaptic responses longer than several hours in slice preparations. To address this question and to investigate possible age-dependency of the action, we analysed effects of a brief application of BDNF and nerve growth factor (NGF) on field potentials of visual cortex in rats of postnatal days 13-17 and 19-24 and in the adulthood for 10-24 h.

Role of NMDA receptor functional domains in excitatory cell death.

The mechanisms by which the NMDA receptor (NMDAR) induces excitotoxicity were investigated using a novel assay. We quantitated the capacity of wild type and mutant receptors for cell killing in CHO cells and cultured cortical neurons by measuring the activity of a co-transfected firefly luciferase expression plasmid. NR1 subunit pore mutations that block Ca(2+) influx, and deletion of the NR1 cytoplasmic C-terminal domain, which functions in Ca(2+) regulation of receptor currents, decreased NMDAR mediated cell killing.

Brain-derived neurotrophic factor enhances long-term potentiation in rat visual cortex.

Brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), members of the nerve growth factor (NGF) gene family, have been suggested to play a role in experience-dependent modification of neural networks in the developing nervous system. In this study we addressed the question of whether these neurotrophins are involved in long-term potentiation (LTP) in developing visual cortex. We recorded layer II/III field potentials and whole-cell currents evoked by test stimulation of layer IV at 0.

Brain-derived neurotrophic factor blocks long-term depression in rat visual cortex.

1. Brain-derived neurotrophic factor (BDNF) has been reported to play a role in long-term potentiation (LTP) in hippocampus, but whether it is involved also in long-term depression (LTD) is not yet known. In this study, we tested whether BDNF and its gene family, nerve growth factor (NGF), have any effect on synaptic transmission and LTD in visual cortical slices of young rats.

Postsynaptic calcium and calcium-dependent processes in synaptic plasticity in the developing visual cortex.

In this paper we describe some of the results obtained from recent experiments on mechanisms underlying long-term potentiation (LTP) and long-term depression (LTD) in the visual cortex of young rats. In particular, we focus on experiments which tested the hypotheses that the induction of LTP in the visual cortex is of Hebbian type and that an input-associated Ca2+ rise at postsynaptic sites and subsequent activation of protein kinases or protein phosphatases may play roles in the induction of LTP or LTD in the developing visual cortex.

Selective acid vulnerability of dopaminergic neurons and its recovery by brain-derived neurotrophic factor.

Among the pathogenetic phenomena of Parkinson's disease, the character of the selective degeneration of nigrostriatal system with severe gliosis is not fully understood. Here, we have shown that dopaminergic neurons may be exclusively sensitive to elevated acidity elicited after the addition of glial mitogenic factors such as epidermal growth factor and basic fibroblast growth factor or after the direct treatment with hydrochloric acid. The acid sensitivity was specific to dopaminergic neurons.

Interleukin-1 beta enhances survival and interleukin-6 protects against MPP+ neurotoxicity in cultures of fetal rat dopaminergic neurons.

To investigate the relationships between the central nervous system and interleukins, ventral mesencephalic cells from embryonic 17-day-old rats were cultured for 3 days in vitro (DIV) and exposed to interleukin-1 beta (IL-1 beta), interleukin-3 (IL-3), or interleukin-6 (IL-6) for the following 2 or 3 DIV with or without 2 microM 1-methyl-4-phenylpyridinium (MPP+). Thus, the survival of and the MPP+ neurotoxicity against the dopaminergic neurons immunostained with anti-tyrosine hydroxylase antibody were examined. For the survival studies, IL-1 beta has been shown to have a survival-promoting effect on dopaminergic neurons.

Survival of and 1-methyl-4-phenylpyridinium (MPP+) neurotoxicity against dopaminergic neurons in coculture of rat mesencephalon with their target on non-target regions.

It is known that dopaminergic neurons in the substantia nigra of the mesencephalon mainly project to the corpus striatum and neocortex, while the hippocampus receives major cholinergic projection from the septum. In the present study, the ventral mesencephalon was cocultured with target regions of its dopaminergic neurons, the striatum and neocortex, and with non-target regions, the hippocampus, thalamus, colliculus and cerebellum, using embryonic day-17 (E17) rats. Thus, the effects of coculture on the survival and the 1-methyl-4-phenylpyridnium (MPP+) neurotoxicity of dopaminergic neurons were investigated.

Involvement of free radicals in MPP+ neurotoxicity against rat dopaminergic neurons in culture.

To examine the mechanisms of the neurotoxicity of 1-methyl-4-phenylpyridinium (MPP+) against dopaminergic neurons, ventral mesencephalic cells from embryonic rats were cultured and exposed to MPP+ with various antioxidants or glutamate receptor antagonists to investigate the participation of free radicals and glutamate, respectively. Such antioxidants as vitamin E, vitamin C, coenzyme Q10, and catalase, but neither allopurinol nor superoxide dismutase, alleviated the MPP(+) -induced death of dopaminergic neurons, while glutamate receptor antagonists did not alter MPP+ neurotoxicity. These findings suggest the participation of free radicals, particularly hydroxyl radicals rather than superoxides, in the process of dopaminergic neuronal death evoked by MPP+.

Death of cultured postnatal rat CNS neurons by in vitro hypoxia with special reference to N-methyl-D-aspartate-related toxicity.

We have established an in vitro hypoxia model using cultured central nervous system neurons from postnatal 4-day-old (P4) rats, in which death may be correlated with N-methyl-D-aspartate (NMDA)-related toxicity. P4 rat hippocampal and neocortical neurons in culture were prevented from death by the addition of MK-801, an NMDA receptor antagonist, and also partially by the removal of calcium ions from the medium, suggesting that NMDA receptors were associated with neuronal death in this in vitro hypoxia model. The neuronal death induced by the model was attenuated by the addition of alpha-tocopherol, indicating that free radicals emerged after hypoxia.

Enhancement of choline acetyltransferase activity in coculture of rat septal and hippocampal neurons.

We report that choline acetyltransferase (ChAT) activity and neuronal survival were enhanced in rat septal neurons cocultured with hippocampal neurons. The enhancement of ChAT activity also occurred as a result of the addition of hippocampal conditioned medium (HpCM). When septal neurons from embryonic day 17 (E17) rats were cocultured with hippocampal neurons, ChAT activity was increased 2-fold compared with homogeneous culture of septal neurons.

In vitro model of hypoxia: basic fibroblast growth factor can rescue cultured CNS neurons from oxygen-deprived cell death.

We established an in vitro hypoxia model and investigated the protective effect of basic fibroblast growth factor (bFGF) against neuronal cell death caused by hypoxia. Hippocampal neurons obtained from rats on embryonic day (E) 17 and 20 and on postnatal day (P) 4 were cultured for 6-24 h in an oxygen-deprived state. This in vitro hypoxia study showed that the cultured neurons were sensitive to the oxygen deprivation.

Basic fibroblast growth factor rescues CNS neurons from cell death caused by high oxygen atmosphere in culture.

In the present study, we cultured rat CNS neurons and tested the neurotrophic support provided by basic fibroblast growth factor (bFGF) to prevent the oxygen-induced neuronal cell death. When rat basal forebrain (septum and vertical limb of diagonal band of Broca) cells of embryonic day 20 were cultured in a serum-free medium containing 5 microM cytosine arabinoside in a 50% oxygen atmosphere, the neuronal cells, which were immunostained by an anti-microtubule-associated protein 2 (MAP2) antibody, gradually died after 1 day in culture. After 3.