Distribution of brain derived neurotrophic factor (BDNF) immunostaining along the C2–C5 spinal cord in adult rats

Abstract

BDNF is a powerful modulator of neuroplasticity and can be found across the rostral‐caudal extent of the spinal neuroaxis in neurons, astrocytes and microglia. BDNF is necessary and sufficient to drive plasticity in the phrenic motor system, likely through either pre‐ and/or post‐synaptic actions on phrenic motoneurons. To our knowledge, the relative distribution of BDNF expression across this region of the mid‐cervical spinal cord has not been systematically “mapped”. Accordingly, in ongoing experiments, we are quantitatively evaluating the distribution of BDNF positive neurons in the C2–C5 spinal cord in adult Sprague‐Dawley rats. The guiding hypothesis is that BDNF will be most prevalent in the C3‐5 ventral horn in the region of the phrenic motor nucleus. Tissues were harvested from adult male rats and processed with standard immunochemistry methods using a BDNF antibody (Alomone, 1:500 dilution). Control experiments showed an absence of spinal cord staining when tissues were incubated without the primary antibody and while keeping all other aspects constant. A custom MATLAB code was used to quantify the number of BDNF positive cells throughout C2–C5. Specifically, BDNF expressing soma were identified as areas with fluorescent intensity above a common threshold. To separate putative neurons, identified regions were sorted by size and only regions with an area of 250–1500 μm2 were included for further analysis. We observed BDNF expression within neurons in laminae I, II, VII, VIII, and IX across the mid‐cervical spinal cord. Further, the number of BDNF positive neurons increased in a rostral to caudal manner from C2 to C5 (P<0.05). There were more BDNF expressing neurons located in the ventral horn when compared to the dorsal horn across C2–C5 (p< 0.01). Finally, smaller BDNF positive cells were evident throughout the gray and white matter which is consistent with microglial distribution in the spinal cord, however, this staining has not been verified at this time. These initial results suggest that naturally occurring levels of BDNF vary across the cervical spinal cord, and are greatest in the region of the phrenic motor nucleus.Support or Funding Information1R01HL139708‐01A1 (DDF), T32‐HD043730 (MDS).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.