Application of low-frequency photostimulation of parvalbumin interneurons to control epileptiform activity in the hippocampus
- Authors: Trofimova A.M.1, Postnikova T.Y.1, Proskurina E.Y.1, Zaitsev A.V.1
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Affiliations:
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
- Issue: Vol 18, No 4 (2023)
- Pages: 782-785
- Section: Conference proceedings
- URL: https://genescells.ru/2313-1829/article/view/623342
- DOI: https://doi.org/10.17816/gc623342
- ID: 623342
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Abstract
Low-frequency electrical stimulation of the brain is used to suppress seizure activity in people with resistant forms of epilepsy [1]. Low-frequency stimulation of certain cell types, such as optogenetic activation of inhibitory parvalbumin (PV) interneurons, can be considered as a promising method for treatment of resistant forms of epilepsy [2]. In this work, we investigated the effect of PV interneuron photostimulation on epileptiform activity in the mouse hippocampus and entorhinal cortex.
This work was performed on 4-month-old B6.129P2-Pvalbtm1(cre)Arbr/J (JacksonLab) mice expressing Cre recombinase in PV interneurons. Adenoassociated viral construct (AAV9-EF1a-DIO-hChR2(H134R)-mCherry) carrying the canalorhodopsin type 2 gene (ChR2) was injected into the CA1 field of the hippocampus at the border with the entorhinal cortex using stereotactic coordinates (AP: -4 mm, ML: 3.5 mm, DV: -3.5 mm). Experiments were performed after 4-5 weeks on surviving brain slices. ChR2-expressing interneurons were activated by 470-nm wavelength light using a laser diode-fiber light source. Epileptiform activity was induced in the slice by application of pro-epileptic solution with 4-aminopyridine (100 μM). Biophysical properties of neurons were recorded by the patch-clamp method in a whole-cell configuration. Epileptiform activity in the slice was recorded by the field potential withdrawal method.
We determined the optimal frequency and duration of photostimulation affecting epileptiform activity in the hippocampus of mice. We tested how PV interneuron photostimulation affects pyramidal neurons in the hippocampus using the patch-clamp method. The following parameters were assessed: intensity, duration, and frequency of PV interneuron photostimulation under normal conditions. Thus, at low photostimulation frequency we observed synchronized responses of the pyramidal cells. And the optimal duration of photostimulation should not have exceeded 25 ms. Then we decided to check how the selected photostimulation parameters affect the seizure activity in the slice. For this purpose, we used the method of recording field potentials. In the CA1 field of the hippocampus, photostimulation with a frequency of 1 Hz and a light flash duration of 10 ms induced regular interictal activity. This induced interictal activity completely suppressed the occurrence of ictal discharges in the brain slice. After cessation of photostimulation, the frequency of intrinsic epileptic-like events in the CA1 field of the hippocampus decreased compared with the pre-stimulatory level.
We found that photostimulation of PV interneurons results in discharges in response to light turn off, indicating synchronous activation of pyramidal neurons. Low-frequency photostimulation of PV interneurons is more effective in modulating epileptiform activity in the CA1 field of the hippocampus. The use of low-frequency optogenetic stimulation of PV interneurons seems to be a promising approach in the control and suppression of seizure activity.
Full Text
Low-frequency electrical brain stimulation is used to reduce seizure activity in individuals with intractable forms of epilepsy [1]. Promising treatment methods for resistant forms of epilepsy involve low-frequency stimulation of specific cell types, including inhibitory parvalbumin (PV) interneurons through optogenetic activation [2]. The present study examined the impact of PV interneuron photostimulation on epileptiform activity in the entorhinal cortex and mouse hippocampus.
This experiment was conducted using 4-month-old B6.129P2-Pvalbtm1(cre)Arbr/J (JacksonLab) mice with Cre recombinase expression in PV interneurons. The CA1 field of the hippocampus, at the border with the entorhinal cortex, was injected with Adenoassociated viral construct (AAV9-EF1a-DIO-hChR2(H134R)-mCherry) containing canalorhodopsin type 2 gene (ChR2) using stereotactic coordinates (AP: –4 mm, ML: 3.5 mm, DV: –3.5 mm). Experiments were conducted on surviving brain slices 4-5 weeks after harvesting. ChR2-expressing interneurons were stimulated using a laser diode-fiber light source emitting 470-nm wavelength light. Pro-epileptic solution containing 4-aminopyridine (100 μM) was applied to induce epileptiform activity in the slice. The patch-clamp method in a whole-cell configuration was used to record the biophysical properties of neurons, while the field potential withdrawal method was used to record epileptiform activity.
We determined the optimal frequency and duration of photostimulation that affects epileptiform activity in the hippocampus of mice. We conducted a patch-clamp study to examine the effects of PV interneuron photostimulation on pyramidal neurons in the hippocampus. Under normal conditions, the intensity, duration, and frequency of PV interneuron photostimulation were evaluated. Thus, we observed synchronized responses of the pyramidal cells at low photostimulation frequency. The optimal duration of photostimulation should not exceed 25 ms. We sought to investigate the impact of selected photostimulation parameters on seizure activity in a slice. We recorded field potentials and analyzed their patterns. In the CA1 field of the hippocampus, we observed that photostimulation with a frequency of 1 Hz and a light flash duration of 10 ms induced regular interictal activity that suppressed the occurrence of ictal discharges in the slice. In the CA1 field of the hippocampus, we observed that photostimulation with a frequency of 1 Hz and a light flash duration of 10 ms induced regular interictal activity that suppressed the occurrence of ictal discharges in the slice. After the photostimulation stopped, the frequency of intrinsic epileptic-like events in the hippocampus’ CA1 field decreased in comparison to the pre-stimulation level.
Photostimulation of PV interneurons leads to discharges in response to the deactivation of light, indicating synchronous activation of pyramidal neurons. Low-frequency photostimulation of PV interneurons is more effective in modulating epileptiform activity in the CA1 field of the hippocampus. The use of low-frequency optogenetic stimulation of PV interneurons appears to be a promising method for controlling and suppressing seizure activity.
ADDITIONAL INFORMATION
Authors’ contribution. All authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work.
Funding sources. This work was supported by Russian Science Foundation grant No. 23-25-00427.
Competing interests. The authors declare that they have no competing interests.
About the authors
A. M. Trofimova
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Author for correspondence.
Email: alina.trofimova1132@mail.ru
Russian Federation, Saint Petersburg
T. Yu. Postnikova
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: alina.trofimova1132@mail.ru
Russian Federation, Saint Petersburg
E. Yu. Proskurina
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: alina.trofimova1132@mail.ru
Russian Federation, Saint Petersburg
A. V. Zaitsev
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: alina.trofimova1132@mail.ru
Russian Federation, Saint Petersburg
References
- Lim SN, Lee CY, Lee ST, et al. Low and high frequency hippocampal stimulation for drug-resistant mesial temporal lobe epilepsy. Neuromodulation. 2016;19(4):365–372. doi: 10.1111/ner.12435
- Proskurina EY, Chizhov AV, Zaitsev AV. Optogenetic low-frequency stimulation of principal neurons, but not parvalbumin-positive interneurons, prevents generation of ictal discharges in rodent entorhinal cortex in an in vitro 4-aminopyridine model. Int J Mol Sci. 2022;24(1):195. doi: 10.3390/ijms24010195
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