Characterization of brain-derived neurotrophic factor following acute, pentylenetetrazol-induced seizures in rats Public
Ding, Kevin (2017)
Published
Abstract
Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and plays diverse roles in enhancing excitatory neural transmission, long term potentiation, axonal growth, and dendritic development. In the context of epilepsy, BDNF protein levels in the hippocampus have repeatedly been shown to increase following status epilepticus and kindling seizures in rodents. Moreover, inhibiting downstream BDNF signaling pathways effectively prevents the development of spontaneous seizures. To our knowledge, BDNF expression has not been characterized following acute, pentylenetetrazol(PTZ)-induced non-status epilepticus seizures. As PTZ is one of the most commonly used chemiconvulsants for anti-epileptic drug screening, it is important to understand the relevance of BDNF and neuroplasticity in this model. If we can show that hippocampal BDNF protein levels increase following acute, PTZ seizures, quantification of BDNF post-seizure can also serve as a physiologically relevant biomarker for seizure intensity. We hypothesized that following acute, PTZ-induced seizures in rats, BDNF levels will increase 2 hours post-seizure. To test our hypothesis, we injected rats intraperitoneally with a convulsive PTZ dosage and sacrificed them at 1, 2, and 24 hours post-seizure. We used an enzyme-linked immunoabsorbance assay (ELISA) to quantify hippocampal and cortical BDNF protein levels. PTZ-induced acute seizures did not lead to any significant changes in hippocampal or cortical levels of BDNF protein compared to saline treated controls. However, we found significantly different levels of BDNF amongst the three times points in both saline and PTZ-treated rats. We followed up with immunohistochemical staining for BDNF and c-fos at the 2-hour time point, where we saw the largest, albeit nonsignificant, increase in BDNF. Qualitative analysis of immunohistochemical staining revealed that BDNF remained primarily somatic in both saline and PTZ treated rats, and was localized to the CA1-CA3 pyramidal layers. C-fos staining showed that neuronal activation from PTZ seizures occurs primarily in the granule cell layer of the dentate gyrus. Together, these results suggest that acute, PTZ-induced seizures may not be sufficiently relevant to the pathophysiology of human epileptic seizures to be used as the first-line screening model for the development of anti-epileptic drugs.
Table of Contents
Table of Contents
Abbreviations.………………………………………………………………………….……….…..1
Introduction…………………………………………………………………………….…..….……2
Background and Pathophysiology of Epilepsy………………………………………........……2
Current Treatments………………………………………………………………..…...........……4
Rodent Models of Seizures and Epilepsy………………………………………….......….……5
Brain Derived Neurotropic Factor and the TrkB Receptor……………………......……..……7
BDNF and Trk in Epilepsy……………………………………………….………...........….……8
Human Studies, BDNF as a Biomarker………………………….……………........…….……11
Rationale……………………………………………………………………….…...….…….……11
Hypothesis…………………………………………………………………….……….…….……12
Materials and Methods………………………………………………………….........…….……12
Animals……………………………………………………………….……….……..............……12
Pentylenetetrazol acute seizure model…………………………………………........…...……12
ELISA Quantification of BDNF…………………………………………………….............……13
BCA protein assay for total protein quantification……………………………........….………14
BDNF Immunohistochemistry and Imaging……….…….………………………..........………15
Statistical Analysis…………………………….………………………………….............………15
Results………………………………………………………………………………...……………16
Hippocampal BDNF expression…………........…………………………………...........………16
Cortical BDNF expression………………………………………………………............….……17
Discussion……………………………………………………………..…………..………………18
Maintenance of BDNF levels post-seizure……………………………..…….........…………..18
BDNF changes over time………………………………………………...……...........…....……20
Future directions……………………………………………………………….…............………20
Conclusion……………………………………………………….…………….…..………………21
Figures………………………………………………………………………….…..…………...…22
Figure 1...............................................................................................................................22
Figure 2...............................................................................................................................23
Figure 3...............................................................................................................................24
Figure 4...............................................................................................................................25
Figure 5...............................................................................................................................26
Figure 6...............................................................................................................................27
Figure 7...............................................................................................................................28
Works Cited……………………………………………………………...………..………………29
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