Investigation of the Potential Therapeutic Use of Brevetoxin to Promote Ischemic Stroke Recovery
Authors: Sequeira Erica , Pierce Marsha , Gomez Dina , Murray Thomas 
Published: June 2021

OBJECTIVE

The challenge for improving stroke recovery is to understand how to optimally engage and modify the surviving neuronal networks to promote recovery. Voltage gated sodium channel activators, such as brevetoxin (PbTx‐2), elevate [Na+]i and mimic activity‐dependent synaptic plasticity by potentiating N‐methyl‐d‐aspartate (NMDA) mediated calcium influx, neurite outgrowth and synaptogenesis in immature cerebrocortical neurons. Normal brain function ceases within seconds after interruption of blood supply and neurons are irreversibly damaged, involving a phase of excitotoxicity. This phase is immediately followed by a recovery phase in which the brain region adjacent to the stroke damaged area, the peri‐infarct zone, shows heightened neuroplasticity. Because the processes involved in recovery after stroke are similar to those regulating development, we propose to use PbTx‐2 as a pharmacological strategy to augment neuronal plasticity and motor function in a murine photothrombotic stroke model.

HYPOTHESIS

We hypothesized that PbTx‐2 would promote stroke recovery by enhancing (1) motor recovery of the affected limb (2) dendritic arbor complexity and excitatory synapse density of the pyramidal neurons in the peri‐infarct region.

EXPERIMENTAL DESIGN

A photothrombotic stroke was produced by administration of Rose Bengal solution followed by a 12.5 min light illumination of the motor cortex region resulting in clotting and infarct in YFP‐H mice. Epicortical application of hydrogel (controls) or hydrogel + PbTx‐2 was applied over the infarct area on day 5 post‐stroke. A pasta matrix reach task was used to assess the ability of mice to grasp pasta pieces to determine the number of pieces of pasta retrieved post‐stroke and post‐treatment . A second motor test, the foot fault test, was performed using mice freely walking on an elevated wire grid while being recorded by video camera, and manually scored for foot faults. Mice were sacrificed at 24 hours after treatment on day 6 and brains collected for sectioning. These sections were imaged using a Leica confocal microscope and analyzed with Imaris software to measure dendritic arborization. In addition, immunohistochemistry was performed using VGLUT1 and PSD95 as respectively pre‐ and post‐synaptic markers to measure excitatory synapse density in the peri‐infarct region.

RESULTS

The number of pasta pieces retrieved was significantly impaired on day 1 post‐stroke in all animals confirming the impact of the stroke. There was subsequent improvement of this task following treatment with PbTx‐2 as compared to the vehicle (hydrogel) controls on day 6. In addition, the PbTx‐2 treated mice had a decrease in the % of foot faults in comparison to the controls on day 6. PbTx‐2 treated pyramidal neurons in the peri‐infarct region had a two‐fold increase in dendritic arbor complexity as compared to controls. Preliminary immunostaining data suggest that the synapse density in the peri‐infarct region was increased in PbTx‐2 treated mice compared to the control mice.

CONCLUSION

Preclinical research in a murine stroke model provided functional and neuronal structural assessments of neural insult‐induced deficits and PbTx‐2 augmented recovery

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.