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Stimulus-evoked high frequency oscillations are present in neuronal networks on microelectrode arrays.

Hales CM, Zeller-Townson R, Newman JP, Shoemaker JT, Killian NJ, Potter SM - Front Neural Circuits (2012)

Bottom Line: As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away.Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation.Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Center for Neurodegenerative Diseases, Emory University, Atlanta GA, USA.

ABSTRACT
Pathological high frequency oscillations (250-600 Hz) are present in the brains of epileptic animals and humans. The etiology of these oscillations and how they contribute to the diseased state remains unclear. This work identifies the presence of microstimulation-evoked high frequency oscillations (250-400 Hz) in dissociated neuronal networks cultured on microelectrode arrays (MEAs). Oscillations are more apparent with higher stimulus voltages. As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away. Oscillations develop across four weeks in vitro. Oscillations still occur in the presence of tetrodotoxin and synaptic blockers, and they cause no apparent disruption in the ability of oscillation-presenting electrodes to elicit directly evoked action potentials (dAPs) or promote the spread of synaptic activity throughout the culture. Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation. Finally, carbenoxolone significantly reduces or eliminates the high frequency oscillations. Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies. This is the first demonstration of stimulus-evoked high frequency oscillations in dissociated cultures. Unlike current models that rely on complex in vivo recording conditions, this work presents a simple controllable model in neuronal cultures on MEAs to further investigate how the oscillations occur at the molecular level and how they may contribute to the pathophysiology of disease.

No MeSH data available.


Related in: MedlinePlus

250–400 Hz oscillation. Average baseline power spectra of electrodes that contain the stimulus-evoked oscillation when a different electrode was stimulated at time 0 (A), with stimulation at time 0 on the electrode with the oscillation (B), and with stimulation at time 0 in the presence of 1 μM TTX (C). (A,B): six cultures (two cortical and four hippocampal, 152 electrodes). (C): three cultures (one cortical and two hippocampal, 106 electrodes); culture age 4–8 weeks.
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Figure 2: 250–400 Hz oscillation. Average baseline power spectra of electrodes that contain the stimulus-evoked oscillation when a different electrode was stimulated at time 0 (A), with stimulation at time 0 on the electrode with the oscillation (B), and with stimulation at time 0 in the presence of 1 μM TTX (C). (A,B): six cultures (two cortical and four hippocampal, 152 electrodes). (C): three cultures (one cortical and two hippocampal, 106 electrodes); culture age 4–8 weeks.

Mentions: Sequential random stimulation at 1 Hz across electrodes of MEAs supporting hippocampal neuronal networks allowed us to identify electrodes that display a stimulus-evoked high frequency oscillation (Figure 1A). This oscillation was still present even when cell medium contained 1 μM TTX (Figure 1B), blocks voltage-dependent sodium channels and eliminates spiking. AMPA, NMDA, and GABA receptor antagonists CNQX, APV, and bicuculline, respectively, did not disrupt the oscillation (Figure 1C). Oscillations were also present in cortical neuronal cultures (Figure 3A) and similarly affected by pharmacological manipulation. The spectral content of the oscillations was calculated over sliding time windows after the stimulus. Average power spectra are presented in Figure 2. The robust oscillation was not present under baseline conditions as represented by the average power spectrum of the oscillation-containing electrode when stimulation occurs on other electrodes (Figure 2A; from n = 152 electrodes). There was a band of increased power between 250 Hz and 400 Hz (Figure 2B; n = 152 electrodes) that persisted in the presence of 1 μM TTX (Figure 2C; 106 electrodes). There was no statistical difference in the oscillation duration (2.40 ± 2.22 s vs. 2.89 ± 2.50 s; p-value = 0.09) between untreated cultures and cultures with TTX (Table 1). The oscillation amplitude was 25.63 ± 7.97 μV in TTX treated cultures while accurate amplitudes could not be determined for oscillations in untreated cultures because of superimposed action potentials. A less intense band of increased power was noted just above 600 Hz.


Stimulus-evoked high frequency oscillations are present in neuronal networks on microelectrode arrays.

Hales CM, Zeller-Townson R, Newman JP, Shoemaker JT, Killian NJ, Potter SM - Front Neural Circuits (2012)

250–400 Hz oscillation. Average baseline power spectra of electrodes that contain the stimulus-evoked oscillation when a different electrode was stimulated at time 0 (A), with stimulation at time 0 on the electrode with the oscillation (B), and with stimulation at time 0 in the presence of 1 μM TTX (C). (A,B): six cultures (two cortical and four hippocampal, 152 electrodes). (C): three cultures (one cortical and two hippocampal, 106 electrodes); culture age 4–8 weeks.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351760&req=5

Figure 2: 250–400 Hz oscillation. Average baseline power spectra of electrodes that contain the stimulus-evoked oscillation when a different electrode was stimulated at time 0 (A), with stimulation at time 0 on the electrode with the oscillation (B), and with stimulation at time 0 in the presence of 1 μM TTX (C). (A,B): six cultures (two cortical and four hippocampal, 152 electrodes). (C): three cultures (one cortical and two hippocampal, 106 electrodes); culture age 4–8 weeks.
Mentions: Sequential random stimulation at 1 Hz across electrodes of MEAs supporting hippocampal neuronal networks allowed us to identify electrodes that display a stimulus-evoked high frequency oscillation (Figure 1A). This oscillation was still present even when cell medium contained 1 μM TTX (Figure 1B), blocks voltage-dependent sodium channels and eliminates spiking. AMPA, NMDA, and GABA receptor antagonists CNQX, APV, and bicuculline, respectively, did not disrupt the oscillation (Figure 1C). Oscillations were also present in cortical neuronal cultures (Figure 3A) and similarly affected by pharmacological manipulation. The spectral content of the oscillations was calculated over sliding time windows after the stimulus. Average power spectra are presented in Figure 2. The robust oscillation was not present under baseline conditions as represented by the average power spectrum of the oscillation-containing electrode when stimulation occurs on other electrodes (Figure 2A; from n = 152 electrodes). There was a band of increased power between 250 Hz and 400 Hz (Figure 2B; n = 152 electrodes) that persisted in the presence of 1 μM TTX (Figure 2C; 106 electrodes). There was no statistical difference in the oscillation duration (2.40 ± 2.22 s vs. 2.89 ± 2.50 s; p-value = 0.09) between untreated cultures and cultures with TTX (Table 1). The oscillation amplitude was 25.63 ± 7.97 μV in TTX treated cultures while accurate amplitudes could not be determined for oscillations in untreated cultures because of superimposed action potentials. A less intense band of increased power was noted just above 600 Hz.

Bottom Line: As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away.Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation.Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Center for Neurodegenerative Diseases, Emory University, Atlanta GA, USA.

ABSTRACT
Pathological high frequency oscillations (250-600 Hz) are present in the brains of epileptic animals and humans. The etiology of these oscillations and how they contribute to the diseased state remains unclear. This work identifies the presence of microstimulation-evoked high frequency oscillations (250-400 Hz) in dissociated neuronal networks cultured on microelectrode arrays (MEAs). Oscillations are more apparent with higher stimulus voltages. As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away. Oscillations develop across four weeks in vitro. Oscillations still occur in the presence of tetrodotoxin and synaptic blockers, and they cause no apparent disruption in the ability of oscillation-presenting electrodes to elicit directly evoked action potentials (dAPs) or promote the spread of synaptic activity throughout the culture. Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation. Finally, carbenoxolone significantly reduces or eliminates the high frequency oscillations. Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies. This is the first demonstration of stimulus-evoked high frequency oscillations in dissociated cultures. Unlike current models that rely on complex in vivo recording conditions, this work presents a simple controllable model in neuronal cultures on MEAs to further investigate how the oscillations occur at the molecular level and how they may contribute to the pathophysiology of disease.

No MeSH data available.


Related in: MedlinePlus