Transcorneal electrical stimulation increases IGF–1 mRNA in the retina in adult rats

Abstract

Abstract: : Purpose: Previously, we demonstrated that transcorneal electrical stimulation(TcES) promotes the survival of axotomized retinal ganglion cells (RGCs) in adult rats. However the mechanism underlying TcES–induced neuroprotection was unclear. Electrical stimulation is known to upregulate trkB and BDNF mRNA in various neurons. We therefore investigated what kind of mRNAs of neurotrophic factors or their receptors are upregulated in the retina after TcES. Methods: TcES (100 µA, 20Hz, 1 hour ) was applied to the left eyes of adult male Wistar rats. Rats were divided into several experimental groups according to the survival periods ranging 1 hour to 7 days after TcES. After certain survival periods, the eyes were enucleated and the retinas were disected and total RNA was obtained from the retinas. RT–PCR analysis was performed to determine the mRNA expressions of the following neurotrophic factors and receptors: BDNF and trkB ; CNTF and CNTF–alpha receptor ; bFGF and FGFR–1 ; IGF–1 and IGF–1 receptor. Results: The RT–PCR analysis showed that the expression of IGF–1 mRNA increased at 1 day after TcES and remained elevated over 7 days after TcES. The expression leveles of the mRNAs of other neurotrophic factors and receptors did not change. Conclusions: IGF–1 mRNA was upregulated in the retina after TcES. This result suggests that IGF–1 may play an important role in the TcES–induced neuroprotection of axotomized RGCs in vivo.

Keywords: neuroprotection • cell death/apoptosis • retina: proximal (bipolar, amacrine, and ganglion cells)