Expression of muscarinic receptor subtypes in tree shrew ocular tissues and their regulation during the development of myopia.

[摘要] Purpose: Muscarinic receptors are knownto regulate several important physiologic processes in the eye.Antagonists to these receptors such as atropine and pirenzepine areeffective at stopping the excessive ocular growth that results inmyopia. However, their site of action is unknown. This study detailsocular muscarinic subtype expression within a well documented model ofeye growth and investigates their expression during early stages ofmyopia induction. Methods: Total RNA was isolated fromtree shrew corneal, iris/ciliary body, retinal, choroidal, and scleraltissue samples and was reverse transcribed. Using tree shrew-specificprimers to the five muscarinic acetylcholine receptor subtypes (CHRM1-CHRM5),products were amplified using polymerase chain reaction (PCR) and theiridentity confirmed using automated sequencing. The expression of thereceptor proteins (M1-M5) were also explored in the retina, choroid,and sclera using immunohistochemistry. Myopia was induced in the treeshrew for one or five days using monocular deprivation of patternvision, and the expression of the receptor subtypes was assessed in theretina, choroid, and sclera using real-time PCR. Results: All five muscarinic receptorsubtypes were expressed in the iris/ciliary body, retina, choroid, andsclera while gene products corresponding to CHRM1, CHRM3,CHRM4, and CHRM5 were present in the corneal samples.The gene expression data were confirmed by immunohistochemistry withthe M1-M5 proteins detected in the retina, choroid, and sclera. Afterone or five days of myopia development, muscarinic receptor geneexpression remained unaltered in the retinal, choroidal, and scleraltissue samples. Conclusions: This study provides acomprehensive profile of muscarinic receptor gene and proteinexpression in tree shrew ocular tissues with all receptor subtypesfound in tissues implicated in the control of eye growth. Despite theefficacy of muscarinic antagonists at inhibiting myopia development,the genes of the muscarinic receptor subtypes are neither regulatedearly in myopia (before measurable axial elongation) nor aftersignificant structural change.

[学科分类] 生物化学/生物物理