Functional Neuroplasticity in the Nucleus Tractus Solitarius and Increased Risk of Sudden Death in Mice with Acquired Temporal Lobe Epilepsy

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Epilepsy News From:

Wednesday, March 28, 2018

Derera ID, Delisle BP, Smith BN, eNeuro (2017), 4(5) e0319-17

Purpose

Description of Study

  • This study was done in experimental rodents. Mice were administered either pilocarpine (a drug that causes epilepsy) or vehicle (these mice did not have epilepsy).
    • Pilocarpine causes status epilepticus (SE); hence, mice that exhibited spontaneous seizures were called “Pilo-SE” mice, whereas the other group of mice belonged to the “Control” group.
    • Learn about the basic science research and the ethics of performing experiments in lab animals.
  • The technique that the scientists performed to investigate properties of neurons in the nucleus tractus solitaries in epileptic mice is called electrophysiology. Using this technique, scientists were able to study whether and how inhibitory (GABAergic) and excitatory (glutamatergic) neurotransmission is different in Pilo-SE mice vs. control mice.
  • Additionally, the heart rate of mice was monitored using ECG (electrocardiography) telemetry. This is because of the cardiorespiratory mechanism that may underlay SUDEP.

Summary of Study Findings

  • The study found that, as expected, Pilo-SE mice experienced spontaneous seizures, and a subset of mice experienced SUDEP.
  • Pilo-SE mice did not show differences in heart rate as compared to the control group.
  • However, the authors did find the following when they examined the nucleus tractus solitaries:
    • In Pilo-SE mice, there was an increase in release of the excitatory neurotransmitter glutamate.
    • There was an enhancement in the inhibitory neurotransmitter system that was dependent on activation of glutamatergic receptors.
    • Changes in excitation and inhibition in the nucleus tractus solitaries structure of the brain that may coincide (and even underlie) epileptogenesis and SUDEP were observed.

What does this mean?

  • Given the suggested role of a failure in the cardiorespiratory system in SUDEP, this study is pertinent because it is among the first to examine alterations in a specific structure - the nucleus tractus solitaries – in the brainstem of experimental mice.
  • More experiments are necessary to clearly show the role of the nucleus tractus solitaries in SUDEP and what these changes in excitation and inhibition mean for someone with temporal lobe epilepsy.

Article published in eNeuro, October 2017.

Authored by: Sloka Iyengar PhD on 3/2018
Reviewed by: Joseph I. Sirven MD on 3/2018

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