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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

Effect of EGTA on the stimulus-evoked oscillation. (A) Sixty seconds of representative SALPA filtered traces at baseline, with 10 mM EGTA and after washout (five days). 0.5 V stimulus (large black arrowhead). (B) Average power spectra showing baseline with TTX 1 μM and (C) after the addition of 10 mM EGTA. 0.5 V stimulus at time 0 (hippocampal culture, age six weeks, n = 22 electrodes).
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Figure 8: Effect of EGTA on the stimulus-evoked oscillation. (A) Sixty seconds of representative SALPA filtered traces at baseline, with 10 mM EGTA and after washout (five days). 0.5 V stimulus (large black arrowhead). (B) Average power spectra showing baseline with TTX 1 μM and (C) after the addition of 10 mM EGTA. 0.5 V stimulus at time 0 (hippocampal culture, age six weeks, n = 22 electrodes).

Mentions: Previous studies showed that gap junction activity is potentiated in low calcium conditions (Jiruska et al., 2010), and there is a model of epilepsy based on this premise (Perez-Velazquez et al., 1994). In this work, low extracellular calcium conditions induced by chelating the calcium in the medium with EGTA, enhanced the stimulus-evoked oscillation with significantly prolonged oscillation durations (Figure 8A and Table 1). The oscillation persisted into the next stimulus trial on electrodes tested, so by using an average time of sixty seconds between trials as a conservative estimate, the calculated p-value was highly significant at 1.13 × 10−113. The amplitude of the oscillation was unchanged (p = 0.23). The stimulus-evoked oscillation returned to a baseline duration following washout (Figure 8A). The average power spectrum showed a slight narrowing of the 250–400 Hz power band (Figures 8B and 8C). Therefore, this oscillation-potentiating effect induced by EGTA provided further support that gap junctions may be responsible for the stimulus-evoked oscillation.


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)

Effect of EGTA on the stimulus-evoked oscillation. (A) Sixty seconds of representative SALPA filtered traces at baseline, with 10 mM EGTA and after washout (five days). 0.5 V stimulus (large black arrowhead). (B) Average power spectra showing baseline with TTX 1 μM and (C) after the addition of 10 mM EGTA. 0.5 V stimulus at time 0 (hippocampal culture, age six weeks, n = 22 electrodes).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: Effect of EGTA on the stimulus-evoked oscillation. (A) Sixty seconds of representative SALPA filtered traces at baseline, with 10 mM EGTA and after washout (five days). 0.5 V stimulus (large black arrowhead). (B) Average power spectra showing baseline with TTX 1 μM and (C) after the addition of 10 mM EGTA. 0.5 V stimulus at time 0 (hippocampal culture, age six weeks, n = 22 electrodes).
Mentions: Previous studies showed that gap junction activity is potentiated in low calcium conditions (Jiruska et al., 2010), and there is a model of epilepsy based on this premise (Perez-Velazquez et al., 1994). In this work, low extracellular calcium conditions induced by chelating the calcium in the medium with EGTA, enhanced the stimulus-evoked oscillation with significantly prolonged oscillation durations (Figure 8A and Table 1). The oscillation persisted into the next stimulus trial on electrodes tested, so by using an average time of sixty seconds between trials as a conservative estimate, the calculated p-value was highly significant at 1.13 × 10−113. The amplitude of the oscillation was unchanged (p = 0.23). The stimulus-evoked oscillation returned to a baseline duration following washout (Figure 8A). The average power spectrum showed a slight narrowing of the 250–400 Hz power band (Figures 8B and 8C). Therefore, this oscillation-potentiating effect induced by EGTA provided further support that gap junctions may be responsible for the stimulus-evoked oscillation.

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