Abstract
Abstract: :
Purpose:We have previously shown that monitoring expression of an immediate early gene, c–fos, in a subpopulation of amacrine cells can provide useful information regarding inner retinal circuitry by applying this technique to mice with defects in the rod visual pathway. However, it is possible that light induced c–fos expression can be attributed to opsin containing cells in the inner retina rather than, or in addition to, rod and/or cone photoreceptors. To address this possibility we have studied the tulp–/– mouse retina which undergoes rapid loss of photoreceptors in the outer retina. Thus, potential contributions from ospin containing cells of the inner retina to c–fos activation can be determined by eliminating all photoreceptors in the outer retina. Methods:After overnight dark adaptation, mice were exposed to a strobe light stimulus presented at 2 Hz for 60 min at 0.4 log cd/sec m2. Three wild–type (WT) and 5 tulp–/– mice were studied. Immediately following light exposure eyes were removed and processed for immunohistochemistry with a c–fos antibody (Santa Cruz Biotechnology). Using light microscopy, c–fos–positive cells were counted in the inner nuclear layer. Results:In WT mice, the number of inner retinal cells labeled for c–fos increased with increasing stimulus intensity. However, c–fos expression was not found in the tulp–/– mouse retina or in dark adapted eyes not exposed to the light stimulus. Conclusions:Under these experimental conditions c–fos activation is predominantly mediated by rod and cone photoreceptor activation. These results support the use of c–fos activation as an assay of inner retinal function and, when applied to mice lacking particular pathways, to elucidate inner retinal circuitry
Keywords: retinal connections, networks, circuitry • amacrine cells • retinal connections, networks, circuitry