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R. D. Glickman, W. R. Elliott, III, N. Kumar, H. Zwick; NF-B Activation Following Laser-Induced Retinal Injury Does Not Prevent Photoreceptor Apoptosis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):552.
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Retinal function following selective laser injury has been studied in the Great Plains rat snake, Elaphe guttata emoryi, using electrophysiological and immunohistological measures. Laser-induced changes in retinal function were characterized with the pattern-evoked electroretinogram (PERG), while the correlation of the transcription factor, NF-ΚB, with retinal cell survival was studied by immunohistology.
In anesthetized animals, PERGs were elicited with counterphased square wave gratings presented by projection into the snake’s eye with a scanning laser ophthalmoscope (SLO). A linear array of 5 suprathreshold lesions was placed near the area centralis with a Nd:VO4 laser (532 nm), which was co-axial with the SLO and delivered 50 mW per 10-msec pulse into the eye. The frequency spectra of PERGs, recorded before and after laser exposure, were determined by Fourier analysis. Animals were sacrificed at 1, 3, and 24 hr post-exposure, and their retinas were probed with commercial antibodies against the p65 component of NF-ΚB, and the apoptosis marker, caspase-9.
Immediately following the placement of the laser lesions, PERGs exhibited frequency doubling, i.e. a new response waveform appeared at twice the stimulus reversal frequency. This frequency-doubled component declined slowly, but did not entirely vanish by the end of the recording session. By 24 hr post-exposure, immunohistological co-localization of p65 and caspase-9 occurred in the laser lesions, especially the photoreceptors.
Histological analysis confirmed that suprathreshold laser exposure caused damage confined to the RPE and photoreceptor cellular layers. The appearance of frequency doubling in the PERG suggests that complementary inputs to the ganglion cells (GC) were disrupted by the laser lesions, thereby unbalancing and introducing harmonic distortion into the GC outputs. The co-localization, in lesioned photoreceptors, of p65 and caspase-9 shows that activation of NF-ΚB, although an anti-apoptotic precursor in other types of neurons, is not necessarily associated with survival in laser-damaged photoreceptors.
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