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Introduction: Throughout life, new neurons are continuously generated in the hippocampus, which is therefore a major site of structural plasticity in the adult brain. We recently demonstrated that extremely low-frequency electromagnetic fields (ELFEFs) promote the neuronal differentiation of neural stem cells in vitro by up-regulating Cav1-channel activity. Objectives: Aim of our study was to determine whether 50 Hz/1mT ELFEF stimulation also affects adult hippocampal neurogenesis in vivo, and if so, to identify the molecular mechanisms underlying this action, and its functional impact on synaptic plasticity. Methods: In adult hippocampus of ELFEF- and sham-exposed mice we performed immunoflourescence, molecular and electrophysiological analyses. Results: ELFEF exposure (1 to 7 h/day for 7 days) significantly enhanced neurogenesis in the dentate gyrus (DG) of adult mice, as documented by increased numbers of cells double-labeled for 5-bromo-deoxyuridine(BrdU) and doublecortin. Quantitative RT-PCR analysis of hippocampal extracts revealed significant ELFEF exposure-induced increases in the transcription of pro-neuronal genes (Mash1, NeuroD2, Hes1) and genes encoding Cav1.2 channel alpha1C subunits. Increased expression of NeuroD1, NeuroD2 and Cav1 channels was also documented by Western blot analysis. Immunofluorescence assays showed that, 30 days after ELFEF stimulation, roughly half of the newly generated immature neurons had survived and become mature dentate granule cells (as shown by their immunoreactivity for both BrdU and NeuN) and were integrated into the granule cell layer of the DG. Electrophysiological experiments demonstrated that the new mature neurons influenced hippocampal synaptic plasticity, as reflected by increased long-term potentiation. Conclusions: Our findings show that ELFEF exposure can be an effective tool for increasing in vivo neurogenesis, and they could lead to the development of novel therapeutic approaches in regenerative medicine.

Introduction: HSV-1 infection may spread within the central nervous system and cause neurological disorders including encephalitis and epileptic seizures. Recurrent HSV-1 infections have also been proposed to play a co-factorial role in the pathogenesis of Alzheimer’s disease. Objective: Aim of our study was to determine the effects of HSV-1 on electrophysiological properties of cortical neurons, and the pathophysiological impact of virally induced changes. Methods: Patch-clamp, immunofluorescence and Western blot experiments were performed on rat cultured cortical neurons either soon after challenge with HSV-1 or 12 24 hours post-infection (hpi). Results: Cell exposure to HSV-1 induced membrane depolarization (11.8±0.7 mV) that triggered action potentials and increased the discharge rate of spontaneously firing neurons (from 0.1±0.1 to 1.1±0.3 Hz). This effect depended on viral binding to neuronal membrane. In fact, when cells were challenged with HSV-1 pretreated with heparin (which prevents the binding of viral glicoproteins to membrane receptors) no depolarization was observed whereas when we applied UV-inactivated HSV-1 (that binds to membrane but is unable to replicate) the observed responses were similar to those produced by active virus. In most neurons, membrane depolarization started soon after HSV-1 application and steady-state was reached after 2 10 s. This effect was due to both inhibition of leak K+ currents and increase of persistent Na+ currents (+53% at 20 mV). Neither transient Na+ currents nor Ca2+ currents were affected. Similar effects were observed 12 hpi. The HSV-1-induced neuronal hyperexcitability triggered intracellular Ca2+ signals promoting APP processing and intracellular and extracellular accumulation of amyloid-b peptide and several neurotoxic APP fragments. Conclusions: Changes in neuronal electrophysiological properties induced by HSV-1 may play a role in the pathophysiology of epileptic seizures and neurodegeneration.

Introduction: In early stages of Alzheimer’s disease, that precede plaque formation and neuronal death, cognitive deficits are likely the result of synaptic function impairment. The key initiating pathogenic event is the accumulation of neurotoxic aggregates of amyloid β-peptide (Aβ) in hippocampus and cortex. We previously demonstrated that the redox state of methionine in position 35 (Met35) plays a critical role in Aβ toxicity. Objective: To determine whether oxidation of Met35 also influences Aβ synaptotoxicity we investigated the effects of 20-min lasting perfusion with 200 nM AβWT and its oxidized analogues (AβMet35(O), AβMet35(O2)) on synaptic transmission and plasticity, and on synaptophysin (Syn) expression. Methods: We performed electrophysiological experiment on hippocampal brain slices and autaptic neurons to study the long-term potentiation (LTP) and synaptic transmission. We also studied Syn density as the ratio between Syn fluorescence intensity and MAP2 labeled area by confocal microscopy. Results: In control slices, 60 min after tetanus fEPSP amplitude (A) and slope (S) were increased by 138% and 132% of baseline, respectively. This potentiation was significantly lower after AβWT treatment (A: +72%; S: +68%; P<0.001) whereas no changes in LTP were observed in slices exposed to AβMet35(O). Surprisingly, AβMet35(O2) reduced the synaptic plasticity to the same level as AβWT. In autaptic microcultures, AβWT and AβMet35(O2) significantly reduced the amplitude of EPSCs evoked by action potentials and mEPSC frequency (P<0.05) whereas AβMet35(O) had no effects on basal synaptic transmission. Finally, AβWT and AβMet35(O2) significantly reduced Syn density while AβMet35(O) did not affect presynaptic terminals. Conclusion: Our results indicate that the chemical state of Met35 plays a key role in Aβ- induced: (i) synaptic depression, (ii) inhibition of synaptic plasticity and (iii) alterations in the expression of proteins relevant for the synaptic function.

Introduction: HSV-1 infection may spread within the central nervous system and cause neurological disorders including encephalitis and epileptic seizures. Recurrent HSV-1 infections have also been proposed to play a co-factorial role in the pathogenesis of Alzheimer’s disease. Objective: Aim of our study was to determine the effects of HSV-1 on electrophysiological properties of cortical neurons, and the pathophysiological impact of virally induced changes. Methods: Patch-clamp, immunofluorescence and Western blot experiments were performed on rat cultured cortical neurons either soon after challenge with HSV-1 or 12 24 hours post-infection (hpi). Results: Cell exposure to HSV-1 induced membrane depolarization (11.8±0.7 mV) that triggered action potentials and increased the discharge rate of spontaneously firing neurons (from 0.1±0.1 to 1.1±0.3 Hz). This effect depended on viral binding to neuronal membrane. In fact, when cells were challenged with HSV-1 pretreated with heparin (which prevents the binding of viral glicoproteins to membrane receptors) no depolarization was observed whereas when we applied UV-inactivated HSV-1 (that binds to membrane but is unable to replicate) the observed responses were similar to those produced by active virus. In most neurons, membrane depolarization started soon after HSV-1 application and steady-state was reached after 2 10 s. This effect was due to both inhibition of leak K+ currents and increase of persistent Na+ currents (+53% at 20 mV). Neither transient Na+ currents nor Ca2+ currents were affected. Similar effects were observed 12 hpi. The HSV-1-induced neuronal hyperexcitability triggered intracellular Ca2+ signals promoting APP processing and intracellular and extracellular accumulation of amyloid-b peptide and several neurotoxic APP fragments. Conclusions: Changes in neuronal electrophysiological properties induced by HSV-1 may play a role in the pathophysiology of epileptic seizures and neurodegeneration.