Spinal Cord Injury Induces Changes in Electrophysiological Properties and Ion Channel Expression of Reticulospinal Neurons in Larval Lamprey

Abstract

In larval lamprey, hemitransections were performed on the right side of the rostral spinal cord to axotomize ipsilateral reticulospinal (RS) neurons. First, at short recovery times (2-3 weeks), uninjured RS neurons contralateral to hemitransections fired a smooth train of action potentials in response to sustained depolarization, whereas axotomized neurons fired a single short burst or short repetitive bursts. For uninjured RS neurons, the afterpotentials of action potentials had three components: fast afterhyperpolarization (fAHP), afterdepolarizing potential (ADP), and slow AHP (sAHP) that was attributable to calcium influx via high-voltage-activated (HVA) (N-and P/Q-type) calcium channels and calcium-activated potassium channels (SKKCa). For axotomized RS neurons, the fAHP was significantly larger than for uninjured neurons, and the ADP and sAHP were absent or significantly reduced. Second, at relatively long recovery times (12-16 weeks), axotomized RS neurons displayed firing patterns and afterpotentials that were similar to those of uninjured neurons. Third, mRNA levels of lamprey HVA calcium and SKKCa channels in axotomized RS neurons were significantly reduced at short recovery times and restored at long recovery times. Fourth, blocking calcium channels in uninjured RS neurons resulted in altered firing patterns that resembled those produced by axotomy. We demonstrated previously that lamprey RS neurons in culture extend neurites, and calcium influx results in inhibition of neurite outgrowth or retraction. Together, these results suggest that the downregulation of Ca 2ϩ channels in axotomized RS neurons, and the associated reduction in calcium influx, maintain intracellular calcium levels in a range that is permissive for axonal regeneration.

Applications of Piezoelectricity in Nanomedicine

“…Several in vitro and in vivo studies have shown that electrical stimulation plays an important role in neurite extension and the regeneration of transected nerve ends [95][96][97]. We have shown as the combination of a non-invasive, wireless stimulation with US in the presence of piezoelectric nanoparticles incubated with cells, is able to elicit the same phenomena derived from a "classical" electric stimulation, i.e., a markedly pronounced outgrowth of neuronal processes in PC12 cultures.…”

Chondroitin Sulfates Act as Extracellular Gating Modifiers on Voltage-Dependent Ion Channels

“…However, a recent work on lamprey neurones [38] indicates that an increase in calcium current through L-type calcium channels results in an inhibition of neurite outgrowth. The same increase in calcium current is seen in a CS4 enriched environment, as our data suggest (Figure 4), and thus it is not possible to completely rule out the possibility that CSs could also act on axonal regeneration via a surface screening effect.…”

Dynamic Manipulation of Hydrogels to Control Cell Behavior: A Review

“…For example, under an applied potential difference, osteoblast-like cells migrate toward negative electrodes, whereas osteoclasts migrate toward positive electrodes. 70 Several in vitro and in vivo studies have shown that ES plays a critical role in neurite extension and regeneration of functional nerve connections, 71,72 promoting nerve regeneration in gaps less than 7 mm. 73 ES is also capable of inducing changes in cell shapes and for promoting cell alignment along the direction of ES application.…”