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J. Carnes, A. G. Holt; Changes in Opioid Receptor and NOS Isozyme Expression in Ciliary Bodies From Sprague Dawley Rats Following Acute Morphine Treatment. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1641. doi: https://doi.org/.
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Previous studies in our laboratory have demonstrated a role of nitric oxide in morphine-induced reduction of intraocular pressure (IOP). More recent studies have demonstrated the ability of morphine to stimulate an increase in the levels of nitric oxide (NO) in aqueous humor. The aim of the present study is to determine the effect of acute morphine treatment on opioid receptor and nitric oxide synthase (NOS) expression in the ciliary body, the site of aqueous humor production.
Experiments were conducted using male Sprague Dawley rats. One group of animals was treated with morphine (100µg/25µl) that was applied topically to both eyes while a second group, age-matched controls, received vehicle (normal saline) in the same manner. Two hours following treatment, the animals were euthanized, ciliary bodies (divided into pools containing 3 animals each) were rapidly dissected and analyzed for changes in expression of opioid receptors (mu, delta and kappa) and NOS isozymes (NOS I and NOS II) using quantitative real time reverse transcription polymerase chain reaction (qRT-PCR).
Ciliary bodies from morphine treated rats showed a 2.7 and 2.0-fold increase in the gene expression levels of mu and kappa opioid receptors, respectively. In contrast, the level of expression of delta opioid receptors was reduced by 2-fold. The expression of NOS I and NOS II isozymes increased by 1.6 and 3.0-fold, respectively, in morphine-treated animals. Preliminary immunohistochemical data demonstrated that the NOS isozymes and mu receptors are produced in the ciliary body and are primarily localized to the ciliary processes. We are currently evaluating the effect of morphine administration on the production and localization of opiate receptors and NOS.
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