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BT Reed, CE Strang, LM Brockway, FR Amthor, KT Keyser; MLA Sensitivity in the Rabbit Retina is Medicated by Functional alpha7 nAChRS . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4770.
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Purpose:α7 nAChRs are present and functional in the developing mammalian retina (Edwards & Cline 1999). However, there is controversy about whether expression and function of α7 nAChRs is retained in adult retina (Baldridge, 1996; Neal et al., 2001). Previous experiments have demonstrated that there are ganglion cells in the rabbit retina that show sensitivity to nanomolar concentrations of the α7 specific antagonist MLA (Reed et al., 2000, 2001). This study was part of an effort to clarify the identity of MLA sensitive receptors in rabbit retina. Methods:Standard extracellular recording techniques were used to record light responses of rabbit ganglion cells (GC) during exposure to the α7-specific antagonist MLA in an everted eyecup preparation. For RT-PCR analysis, total RNA was extracted from the hippocampus of dutch-belted rabbit and from the retinas of dutch-belted and albino rabbits. Primers based on the human α7 cDNA (genbank accession number U40583) sequence were used to amplify the coding region 140-602. The resulting products were sequenced and compared for cross-species and cross-receptor homology. Results:Nanomolar doses of MLA affected light responses of both ON and OFF brisk transient GCs and directionally selective GCs. RT-PCR products showed 91% sequence homology with human and rat α7 cDNA, while showing no significant homology with the DNA of other receptor types. Conclusion:The detection of mRNA with high sequence homology to human α7 cDNA supports the premise that the MLA sensitivity in GCs in the rabbit retina is mediated by functional α7 nAChRs.
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