C-Fibers Are Not Necessary for the Development of Pain-Induced Hemorrhage Following SCI
Abstract
Spinal cord injuries (SCI) are commonly accompanied by additional injuries (polytrauma), such as lacerations, bone fractures, and burns. These injuries serve as origins for pain (nociceptive) input to the spinal cord. Previous work has shown that this nociceptive input undermines locomotor recovery and exacerbates the infiltration of blood into the spinal cord (hemorrhage) after injury. Hemorrhage within the spinal cord then further damages the tissue, leading to an increase in the size of injury. Prior studies have found that engaging nociceptive fibers through intermittent electrical stimulation (shock), or application of the irritant capsaicin, is sufficient to induce hemorrhage in the spinal cord. While electrical stimulation activates both myelinated A-delta and unmyelinated C-fibers, capsaicin selectively binds C-fibers through the transient receptor potential vanilloid receptor-1 (TRPV-1). Therefore, as C-fiber activation has been shown to be sufficient to induce hemorrhage, this study served to determine if it is necessary. To eliminate C-fibers while leaving A-delta fibers intact, three excitotoxic doses of capsaicin were administered 12 hours apart. Thirteen days later, rats received a moderate T12 contusion injury. The next day they were exposed to intermittent tail shock or nothing (unshocked). Locomotor scores and hemodynamic measurements were collected at 3 one-hour time points following nociceptive stimulation. Rats were then sacrificed, and the injured region of the spinal cord was collected for tissue analysis. Drabkin’s assay was used to measure hemoglobin content in each sample. Ablating C-fibers attenuated the cardiovascular response to nociceptive stimulation and its adverse effect on locomotor performance. It did not, however, attenuate pain-induced hemorrhage.
Citation
Lout, Emerson (2020). C-Fibers Are Not Necessary for the Development of Pain-Induced Hemorrhage Following SCI. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /196619.