HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (7) Citing Articles via Google Scholar Google Scholar Articles by Rada, J. A. S. Articles by Wiechmann, A. F. Search for Related Content PubMed PubMed Citation Articles by Rada, J. A. S. Articles by Wiechmann, A. F.

Melatonin Receptors in Chick Ocular Tissues: Implications for a Role of Melatonin in Ocular Growth Regulation

¹From the Departments of Cell Biology and ²Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma.

PURPOSE. The influences of diurnal rhythms involving a variety of ocular parameters are implicated in the development of myopia. The purpose of this study was to determine the expression of the melatonin receptor subtype proteins in chick ocular tissues and to examine the role of the circadian signaling molecule melatonin in normal ocular growth and the exaggerated ocular growth associated with the development of myopia.

METHODS. Expression of the Mel_1a, Mel_1b, and Mel_1c melatonin receptor proteins in ocular tissues was examined by Western blot analyses, slot blot analyses, and immunocytochemistry. For examining the effect of melatonin on ocular growth, chicks were maintained on a 12-hour light–dark cycle and were monocularly form-vision deprived in one eye with a translucent occluder for 5 days. During the 5-day treatment period, chicks were injected systemically during the early dark period with melatonin (0.6 mg) or 2% ethanol vehicle control. Ocular dimensions of normal and deprived eyes were examined by high frequency A-scan ultrasound.

RESULTS. Immunocytochemical analysis of chick ocular tissues revealed the cellular distribution of the Mel_1a receptor subtype in the cornea, choroid, sclera, and retina. Western blot and slot blot analyses demonstrated that all three receptors were present in these tissues and they demonstrated distinct diurnal rhythms of protein expression in the retina-RPE-choroid, with peak levels of Mel_1a and Mel_1b occurring during the night and peak levels of Mel_1c during the day. Systemic administration of melatonin resulted in significant changes in anterior chamber depth, vitreous chamber depth, and choroidal thickness of form-deprived and/or control eyes.

CONCLUSIONS. Results of this study show that all three melatonin receptor subtypes are expressed in retinal and extraretinal ocular tissues of the chick eye. The finding that administration of melatonin alters the growth of several ocular tissues in both control and form-deprived eyes suggests that melatonin, acting through specific melatonin receptors in ocular tissues, plays a role in ocular growth and development. This conclusion suggests that the action of melatonin, combined with expression of melatonin receptors, is involved in the regulation of the diurnal rhythm of ocular growth.

This article has been cited by other articles:

				M. P. Feldkaemper, I. Neacsu, and F. Schaeffel Insulin Acts as a Powerful Stimulator of Axial Myopia in Chicks Invest. Ophthalmol. Vis. Sci., January 1, 2009; 50(1): 13 - 23. [Abstract] [Full Text] [PDF]