Abstract
Purpose: :
Central nervous system (CNS) in adult mammals loses the ability to regenerate after injury. Although electrical stimulation (ES) has been shown to promote neural regeneration, the underlying mechanisms of how ES enhances CNS regeneration remain elusive. The present study was aimed to investigate the effect of ES waveforms on neurite outgrowth of goldfish retinal explants and to elucidate possible cellular mechanisms responsible for the observed ES effects.
Methods: :
The optic nerve of adult goldfish was intraorbitally crushed 7-14 days before retinal explants preparation. The explants were cultured in the laminin-coated ITO conductive device for ES application. Various waveforms of ES were applied to examine its effect on neural regeneration. The effect of calcium, PKC, and IGF-I on neurite outgrowth under ES were also studied using specific inhibitors.
Results: :
When the retinal explants were stimulated for one hour with intermittent pulses at Day 1, the regenerated neurite length was significantly increased compared to those stimulated with continuous square waves or continuous pulses on the same day. We also demonstrated that ES could induce calcium influx through voltage gated calcium channels, and the enhancement of neurite outgrowth after ES application was reduced by protein kinase C (PKC) inhibitor. Moreover, we found that Insulin-like growth factor I (IGF-I) did not further facilitate the ES effect, and ES alone did not rescue neurite outgrowth reduced by inactivating IGF-I receptors.
Conclusions: :
These results suggest that intermittent pulse ES promotes neurite regeneration most effectively in goldfish retinal explants, and ES enhances neurite outgrowth by activating PKC and IGF-I via calcium influx through voltage gated calcium channels.
Keywords: regeneration • ganglion cells • retinal culture