Amplitude Of Evoked Action Potential Research Articles

Anti-effects of cordycepin to hypoxia-induced membrane depolarization on hippocampal CA1 pyramidal neuron

Cordycepin has important neuroprotective effects in hypoxic or ischemic insult. However, the direct electrophysiological evidence of cordycepin's neuroprotection from hypoxic or ischemic insult remains unknown. Hence, in this study, the electrophysiological mechanism by which cordycepin protects against ischemic and hypoxic damages has been studied using an energy-deprivation injury model through whole-cell patch clamp techniques. Results revealed that cordycepin (80µM) significantly delayed hypoxia-induced membrane depolarization, including cordycepin reduced slope, and extended the duration of slow depolarization, prolonged the ability to generate spontaneous action potential (AP) firing, delayed the onset of rapid depolarization, and maintained the more hyperpolarized membrane potential after rapid depolarization. Additionally, cordycepin also delayed the hypoxia-induced decrease in the evoked AP amplitude. Furthermore, cordycepin can rescue the neuronal electrophysiological function after the 5min hypoxia pretreatment insult as seen the recovery on the evoked spike amplitude, membrane potential, and evoked AP latency during reoxygenation of hippocampal slices with cordycepin. Collectively, the results in this study provide direct evidence demonstrating the important neuroprotective effects of cordycepin against the hypoxic insult via improvement of the neuronal electrophysiological function, and the mechanism underlying the anti hypoxia-induced membrane depolarization is strongly recommended.

Developmental studies of electrical properties in cultured rat brain neurons.

The rat brain neurons isolated from 15--17-day embryos were grown in dissociated cell culture and maintained in vitro for 3 weeks. The developmental process of the neurons was observed from the early stage of development in terms of passive and active electrical parameters and their changes induced by perfusion of ionic channel blockers. The neurons' development could be morphologically divided into stages I (from seedling to 6 days), II (7-11 days), III (12-20 days) and IV (21-22 days). The relative values of resting membrane potentials (RMP) for stages I, II, III and IV were 1, 3.46, 4.07 and 6.54, respectively; the corresponding values of input resistance (Rin) were 1, 1.48, 2.53 and 4.56, respectively. The current-voltage relationship in stages II and III was exponential in the direction of depolarization and the Rin's change with time was nearly linear. Spontaneous activities increased with prolongation of culture and the amplitude of evoked action potentials reached the maximum during stages III and IV. The RMP and Rin were markedly decreased by perfusion of TEA while no change was seen in TTX perfusion group. The results indicate that potassium ionic channels develop slower in stages II and IV, faster in stages I and III and mature by the end of stage IV.

Polyglycolic Acid Tubing As a Conduit for Nerve Regeneration

Rabbit common peroneal nerves will regenerate across a 1-cm gap inside polyglycolic acid tubing. Regenerated nerves are separated histologically into "minifascicles," which persist in distal segments. The conduction velocities and evoked action potential amplitudes following this type of regeneration are inferior to those seen in nerves repaired directly or by interpositional grafting. The strength of reinnervated muscles is equal following direct nerve suture, interpositional grafting, or polyglycolic acid conduit repairs.