Abstract
Purpose :
We tested the hypothesis that midline fluid percussion injury (FPI), a model of mild to moderate traumatic brain injury (TBI), causes long-term damage to the anterior visual pathways.
Methods :
Male and naturally cycling female Sprague Dawley rats received either an injury (FPI) or a craniectomy alone (sham). At 35 days post-injury, electroretinograms (ERG), photopic negative responses (PhNR), and visual evoked potentials (VEP) were recorded. Rats were immediately euthanized, and eyes and optic nerves were collected for histological and immunohistochemical analysis. Retina cross-sections were co-labeled with anti-TNFα and anti-GFAP. To quantify the activation of Müller cells in response to injury, we counted anti-GFAP-positive Müller cell processes and measured fluorescence levels.
Results :
VEP amplitude and latency were unaffected by FPI. However, the PhNR amplitude was significantly lower in FPI rats compared to shams, p < 0.0001, and was lower in FPI females compared to FPI males, p < 0.001. In sham rats, TNFα immunolabeling was restricted to the ganglion cell layer (GCL). In contrast, in FPI rats, TNFα-positive cells were detected in the GCL, inner nuclear layer (INL), and outer nuclear layer (ONL). The number of anti-GFAP-positive Müller cell processes was significantly increased in FPI rats compared to shams, p <0.05. FPI females had a greater number of GFAP-positive Müller cell processes compared to FPI males, p < 0.05.
Conclusions :
The results of this study illustrate an inflammatory response in the retina and an effect on retinal ganglion cell function that accompanies diffuse TBI. Interestingly, the results uncovered sex differences the VEP and inflammatory responses that warrant further investigation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.