All ETDs from UAB

Advisory Committee Chair

Kent T Keyser

Advisory Committee Members

Franklin R Amthor

David C Knight

Lori L McMahon

Christianne E Strang

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Acetylcholine receptors (AChRs) are involved in visual processing and are expressed by inner retinal neurons in all species studied to date (Keyser et al., 2000; Dmitrieva et al., 2007; Liu et al., 2009), but their distribution in the mouse retina remains unknown. Reductions in alpha 7 nicotinic AChRs (nAChRs) are thought to contribute to memory and visual deficits observed in Alzheimer's and schizophrenia (Coyle et al., 1983; Nordberg et al., 1999; Leonard et al., 2006). However, the alpha 7 nAChR knockout (KO) mouse has a mild phenotype (Paylor et al., 1998; Fernandes et al., 2006; Young et al., 2007; Origlia et al., 2012). The purpose of this study was to determine the expression of AChRs in wildtype (WT) mouse retina and to assess whether up-regulation of other AChRs in the alpha 7 nAChR KO retina may explain the minimal deficits described in the KO mouse. Reverse-transcriptase PCR (RT-PCR) showed that mRNA transcripts for alpha 2-7, alpha 9, alpha 10, beta 2-4 nAChR subunits and m1-m5 muscarinic AChR (mAChR) subtypes were present in WT murine retina. Western blot analysis confirmed the presence of alpha 3-5, alpha 9, and m1-m5 AChR proteins and immunohistochemical analysis demonstrated nAChR and mAChR proteins expressed by subsets of bipolar, amacrine and ganglion cells. This is the first reported expression of alpha 9 and alpha 10 nAChR transcripts and alpha 9 nAChR proteins in the retina of any species. Quantitative RT-PCR (qPCR) showed changes in AChR transcript expression in the alpha 7 nAChR KO mouse retina relative to WT. Within whole retina alpha 2, alpha 9, alpha 10, beta 4, m1 and m4 AChR transcripts were up-regulated, while alpha 5 nAChR transcripts were down-regulated. However, cell populations showed subtle differences; m4 mAChR transcripts were up-regulated in the ganglion cell layer and outer portion of the inner nuclear layer (oINL),while beta 4 nAChR transcript up-regulation was limited to the oINL. Surprisingly, alpha 2, alpha 9, beta 4, m2 and m4 transcripts were down-regulated in the inner portion of the INL. These results indicate that compensation is mediated by differential regulation of more than one receptor type and changes in mRNA expression vary between cell populations.

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