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G Chidlow, R Casson, M Vidal-Sanz, AJ Bron, NN Osborne; The Effect of Optic Nerve Transection On The Levels of Defined Messenger RNA Species and The Amplitude of the Flash Electroretinogram In the Rat Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4040.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous work from our laboratory has demonstrated that ganglion cell death in the rat retina induced by ischemia or excitotoxicity can be followed by measuring changes in retinal Thy-1 and neurofilament light (NF-L) mRNAs. In this study, we quantified the effect of ganglion cell death induced by axotomy on the retinal levels of various mRNAs, including Thy-1 and NF-L. We also investigated whether axotomy causes an alteration in the electroretinogram (ERG). Methods: Wistar rats received either an ON transection or a sham procedure in one eye, while the fellow eye served as a control. ON transection was performed 3-4 mm from the optic disc without damaging the retinal blood supply. After 7 or 21 days, the rats were killed and total retinal mRNA was extracted. The expression of Thy-1, NF-L, rhodopsin, glyceraldehyde 3-phosphate dehydrogenase (G3PDH), bFGF, BDNF and CNTF were assessed using semi-quantitative RT-PCR. The ERG was recorded before and at various time points after the procedure. Results: Retinas from axotomized eyes killed after 21 days showed dramatic reductions, relative to control eyes, in the levels of Thy-1 and NF-L mRNAs, but rhodopsin mRNA content was unchanged. Moreover, CNTF and bFGF but not BDNF mRNA levels were elevated in the retinas of axotomized eyes. Similar effects were observed in animals killed after 7 days, although the decreases in Thy-1 and NF-L were of slightly lesser magnitude. No differences were apparent in the total retinal levels of any of the mRNA species analysed from sham-operated rats. Preliminary results showed that in axotomized, but not sham-operated, eyes there is a small but significant reduction in the a- and b-waves of the ERG. Conclusion: The present studies show that measurement of total retinal Thy-1 and NF-L mRNAs provides a means of following ganglion cell death after ON transection. Since no changes in any of the mRNAs or the ERG were observed in sham-operated eyes, we can conclude that axotomy does not cause significant disruption of the retinal or optic nerve vasculature. Furthermore, the study confirms that axotomy induces an upregulation of bFGF and CNTF in the retina.
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