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Q. Le, Y. Lu, R. Chu; The Effects of Pirenzepine on the Expression of Type I and Type IV Muscarinic Receptor in the Guinea Pigs . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3320.
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To study the expression of type I and type IV muscarinic receptors on the sclera, choroid and retina of the guinea pigs after the subconjunctival injection of pirenzepine.
10 three–week–old guinea pigs underwent monocular deprivation (MD) with right eyelids surgically sutured and were divided into 2 groups. The animals in one group were subconjunctivally injected with 0.1ml pirenzepine solution (containing 250 mg pirenzepine) in the deprived eye. The other group was left untreated. Another 10 age–matched ones, with their both eyes open, were divided into 2 groups as well. One group was treated with pirenzepine in the right eye, just like the deprived groups, and the other untreated. 2 weeks later, all the animals were sacrificed and had their right eye enucleated. Then immunohistochemical examination were done to detect the changes in the expression of type I and type IV muscarinic receptors on the sclera, choroid and retina in four groups.
No apparent M1 receptor expression were detected in the RPE layer of the animals that underwent monocular deprivation and treated with pirenzepine, compared with other groups. However, the photoreceptors and nerve fiber layer seemed to have an up–regulation of M1 receptor. The expression of M4 receptor was not observed on any layer of the retina, but the up–regulation of its expression was detected on the choroid and sclera.
Pirenzepine could alter the expression of type I and type IV muscarinic receptor, indicating that it might inhibit myopic progression through not only type I muscarinic receptors, but also type IV ones.
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