Recording of Neural Activity With Modulation of Photolysis of Caged Compounds Using Microelectrode Arrays in Rats With Seizures

Objective: In this paper, a new method was established to monitor multichannel neural activity with microelectrode arrays (MEAs) under modulation of caged compounds in a rat model of seizures. Methods: The 16-channel MEAs were fabricated and implanted into the hippocampus of normal rats and epileptic rats for neural spike and local field potential (LFP) recording. Using optical fibers with drug delivery tubing, two different caged compounds [ruthenium-bipyridine-trimethylphosphine glutamate (RuBi-Glu) and ruthenium-bipyridine-trimethylphosphine gamma aminobutyric acid (RuBi-GABA)] were applied, and blue light (465 nm) was used to modulate neural activity. Results: In normal rats, RuBi-Glu excited neural activity, and RuBi-GABA inhibited neural activity. The amplitude of spikes increased 26% from 154 to 194 μV with RuBi-Glu modulation. During RuBi-GABA modulation, spikes recovered to 142 μV. The firing rate increased from 1.4 to 4.5 Hz with RuBi-Glu modulation and decreased to 0.8 Hz after RuBi-GABA modulation. The power of LFPs increased from 566 to 1128 μW with RuBi-Glu modulation and recovered to 710 μW with RuBi-GABA modulation. In epileptic rats, the neural activity during seizures was significantly inhibited by RuBi-GABA modulation. The amplitude of spikes was 242 μV during seizures and decreased to 112 μV with RuBi-GABA modulation. The firing rate decreased from 20.29 to 1.33 Hz with RuBi-GABA modulation. Conclusion: Using MEAs, the modulation of neural activity with caged compound photolysis was observed with high temporal-spatial resolution in normal and epileptic rats. Significance: This new method is important for monitoring neural activity with photo-switchable modulation.