Electrophysiological changes in isolated spinal cord white matter in response to oxygen deprivation

Abstract

Methods: The hypoxic injury was induced by reducing the oxygen tension of the perfused solution by 80%. Compound action potentials (CAPs) were monitored before, during, and after oxygen deprivation. Results: We have found that 60 min of hypoxia reduced the conduction to 30% of preinjury level and recovered to approximately 60% of the preinjury level upon reoxygenation. Larger axons appeared to be more vulnerable to oxygen deprivation. We noted a significant decrease and recovery of the depolarizing afterpotential (DAP). Likewise, there was a delay and recovery of absolute and relative refractory period. Concomitantly, the ability of axons to follow repetitive stimuli was suppressed following oxygen deprivation but recovered upon reoxygenation. Conclusion: Following 60 min of oxygen deprivation and 30 min of reoxygenation, mammalian spinal cord white matter can partially recover electrical impulse conduction. However, within the same period, cords gained a complete recovery of other electrical properties, such as the depression of DAP, the delaying of refractory period, and the decreased ability to respond to repetitive stimuli. Compared to previous findings when both oxygen and glucose were deprived, we conclude that glucose plays a relatively minor role during the acute stage of oxygen deprivation in mammalian spinal cord white matter.

The effects of cyclosporin-A on axonal conduction deficits following traumatic brain injury in adult rats

“…Measurements based on CAP area should best reflect total number of recruited fibers, a factor relevant to pathologies such as TBI, which conceivably may alter activation synchrony and conduction velocity. However, empirical results in our laboratory and others (Pryor and Shi, 2006), have indicted the use of CAP area and CAP peak to yield similar estimates of injury. In the present study, it was useful to use CAP peak to assess responses to 100 Hz stimulus trains, because baselines tended to be less stable during high frequency firing.…”

“…The present observation of a disproportionate CsA benefit for the myelinated axons may reflect a more severe level of mitochondrial pathology in these larger fibers. In this context, it is notable that larger diameter axons have been reported to be more susceptible to oxygen deprivation than smaller fibers, in terms of impulse conduction (Peasley and Shi, 2002; Pryor and Shi, 2006), which was attributed to a relatively greater energy demand in the larger axons. Ultrastructural observations of rat optic nerve also support a preferential vulnerability of large myelinated axons to anoxic injury, associated with mitochondrial swelling and loss of normal cristae (Waxman et al, 1992).…”

Ethyl‐cyanoacrylate is acutely nontoxic and provides sufficient bond strength for anastomosis of peripheral nerves

“…A modified sucrose gap chamber was used to assess sciatic nerve impulse conduction function 7. The endpoints of our functional assessment included compound action potentials (CAP) and latency.…”

“…After curing, fluid levels were returned to normal and electrophysiological recording reestablished. Recordings were made using a bridge amplifier (Neurodata Instruments) and data analysis performed using custom Labview software (National Instruments) on a PC as previously described 7. Instantaneous waveforms and time histories were obtained.…”

Evaluation of the potential killing performance of novel percussive and cervical dislocation tools in chicken cadavers

“…Both manual and mechanical cervical dislocation killing methods are designed to separate the skull from the vertebral column of the bird (ideally C0-C1 vertebral dislocation), resulting in severing of the spinal cord and/or brainstem and the main blood vessels supplying the brain (Gregory and Wotton, 1990;Parent et al, 1992;Veras et al, 2000;Cartner et al, 2007;Mason et al, 2009). It has been suggested that optimal application also produces a concussive effect on the bird due to trauma inflicted on the brainstem through the action of stretching and twisting (Harrop et al, 2001;Shi and Pryor, 2002;Pryor and Shi, 2006;Shi and Whitebone, 2006;Cartner et al, 2007;Erasmus et al, 2010a). However, both methods of cervical dislocation have been the subject of welfare concern, as research in the last 40 years has raised questions about their humaneness and consistency in poultry Wotton, 1986, 1990;Erasmus et al, 2010a), as well as other species (Tidswell et al, 1987;Cartner et al, 2007).…”