Nanodiamonds-induced effects on neuronal firing of mouse hippocampal microcircuits

Fluorescent nanodiamonds (FND) are carbon-based nanomaterials that can efficiently incorporate optically active photoluminescent centers such as the nitrogen-vacancy complex, thus making them promising candidates as optical biolabels and drug-delivery agents. FNDs exhibit bright fluorescence without photobleaching combined with high uptake rate and low cytotoxicity. Focusing on FNDs interference with neuronal function, here we examined their effect on cultured hippocampal neurons, monitoring the whole network development as well as the electrophysiological properties of single neurons. We observed that FNDs drastically decreased the frequency of inhibitory (from 1.81 Hz to 0.86 Hz) and excitatory (from 1.61 Hz to 0.68 Hz) miniature postsynaptic currents, and consistently reduced action potential (AP) firing frequency (by 36%), as measured by microelectrode arrays. On the contrary, bursts synchronization was preserved, as well as the amplitude of spontaneous inhibitory and excitatory events. Current-clamp recordings revealed that the ratio of neurons responding with AP trains of high-frequency (fast-spiking) versus neurons responding with trains of low-frequency (slow-spiking) was unaltered, suggesting that FNDs exerted a comparable action on neuronal subpopulations. At the single cell level, rapid onset of the somatic AP ("kink") was drastically reduced in FND-treated neurons, suggesting a reduced contribution of axonal and dendritic components while preserving neuronal excitability.Comment: 34 pages, 9 figure

Interictal spiking in adult newly-diagnosed focal epilepsy of unknown cause: The effect of age.

OBJECTIVE: To assess the yield of interictal EEG spiking in standard and whole-night sleep EEGs in elderly subjects with recent-onset focal seizures compared to younger patients. METHODS: Detection of interictal epileptiform abnormalities (IEAs) and rating of mean spike index (number of interictal discharges/minute) values for different sleep stages (NREM stages 1-2 and 3-4 and REM sleep) in standard EEG (S-EEG) and 24-h ambulatory EEG (A-EEG) at first referral in three groups of thirty consecutive outpatients [aged 20-39 (young), 40-59 (adults) and ⩾60years (elderly)], retrospectively selected according to a subsequent diagnosis of focal epilepsy of unknown cause, no sleep disorders or drugs or comorbidities affecting sleep and EEG. RESULTS: Elderly subjects showed a lower rate of IEAs on S-EEG (p<0.01) but a higher propensity for spiking during deep NREM sleep, 11/30 showing IEAs exclusively during stages 3-4. Mean spike index showed a significant increase in IEAs between sleep stages 1-2 and 3-4 in the elderly subjects (p<0.001). CONCLUSIONS: A significant association emerged between IEAs during deep sleep and age (p<0.001). SIGNIFICANCE: EEG recordings covering deep NREM sleep should be recommended when IEAs detection is needed to support a diagnosis of epilepsy in elderly subjects