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V. A. Barathi, S. R. Weon, J. H. Kam, J. Wess, R. W. Beuerman; Experimental Myopia in Muscarinic Receptor Knockout Mice: Role of Specific Muscarinic Receptor Subtypes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4418.
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The purpose of this study was to determine if there are differences in the ability to induce form deprivation experimental myopia in a series of mice with specific muscarinic acetylcholine receptor gene knock-outs.
Homozygous M2, M4, and M5 muscarinic receptor mutant mice (-/-) were backcrossed with B6 wild type (+/+) mice to get heterozygous (+/-) mice for further breeding. Tail biopsies were taken to extract DNA and PCR was carried out using specific primers for genotyping. F5 generation mice of M2-/-, M4-/-, M5-/- and wt+/+ mice were used for experiments. Contact lenses were placed over the right eyes of 6 knockout and wild type mice from each strain by gluing on a negative (-10D) contact lens over the eye on post natal day 10. Axial length was measured at 4, 6 weeks and 8 weeks by AC-Master, OLCI (Carl-Zeiss) and at 8 weeks by magnified video image photography. Expression of muscarinic receptor subtypes was detected by western blot and immunohistochemistry.
Axial length (mm) versus age (weeks) was presented in table. M4-/- and M5-/- axial growth was significantly 200 microns longer than the M2-/-. In M2+/+, M4+/+ and M5+/+ mice axial growth was not significantly different. Western blot and immunohistochemistry showed the expression of all five muscarinic receptor subtypes in sclera from wt mice.
The results provide initial evidence that the M4 and M5 muscarinic receptors may contribute more than the M2 receptor in terms of scleral growth in experimental myopia. This study also confirms the presence of all five muscarinic receptor subtypes in mouse sclera.
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