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Endogenous catecholamine concentrations in rat iris-ciliary body
S Hiromatsu1, M Araie, K Fujimori
1Department of Ophthalmology, University of Tokyo School of Medicine.
Japanese Journal of Ophthalmology
|January 1, 1994
Summary
This study measured catecholamines in rat iris-ciliary bodies (ICB). Norepinephrine and dopamine were detected, but epinephrine was not, after using microwave irradiation and HPLC for analysis.
Area of Science:
- Ophthalmology
- Neuroscience
- Pharmacology
Background:
- The iris-ciliary body (ICB) is crucial for ocular functions.
- Understanding endogenous catecholamine levels in the ICB is important for ocular physiology and pharmacology.
Purpose of the Study:
- To quantify endogenous catecholamine concentrations (norepinephrine, dopamine, epinephrine) in the rat iris-ciliary body (ICB).
- To investigate the effect of apraclonidine, an alpha-2 agonist, on ICB catecholamine levels.
Main Methods:
- Microwave irradiation (9.5 kW, 2450 MHz, 0.9 seconds) was used for rapid enzyme inactivation in rat eyes.
- High-performance liquid chromatography (HPLC) was employed to determine catecholamine levels in isolated ICBs.
- Samples consisted of 10 ICBs from 10 eyes, with measurements of norepinephrine, dopamine, and epinephrine.
Main Results:
- Endogenous norepinephrine levels were 19.5 +/- 2.3 nmol/g protein, and dopamine levels were 3.2 +/- 0.2 nmol in the rat ICB.
- Epinephrine was not detected in the rat ICB samples.
- A single 0.05% apraclonidine instillation increased norepinephrine levels in the treated eye's ICB by 8% (P < 0.05) compared to the fellow eye.
Conclusions:
- Norepinephrine and dopamine are present in the rat ICB, while epinephrine is not detectable.
- Topical apraclonidine administration can modulate endogenous norepinephrine levels within the rat ICB.
- These findings contribute to understanding the neurochemistry of the iris-ciliary body and the pharmacology of alpha-2 agonists in the eye.