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Is ocular melatonin regulated by the adrenergic system?
1Department of Medical Pharmacology and Toxicology, Texas A & M University College of Medicine, College Station.
Ophthalmic Research
|January 1, 1987
Summary
Ocular melatonin levels are not regulated by the adrenergic sympathetic nervous system in rabbits or chickens. These findings suggest other neurotransmitters influence melatonin production in the eye.
Area of Science:
- Ophthalmology
- Neuroendocrinology
- Chronobiology
Background:
- Melatonin plays a role in regulating intraocular pressure.
- The sympathetic nervous system regulates melatonin in the pineal gland, but its role in ocular melatonin is unknown.
Purpose of the Study:
- To investigate whether ocular melatonin levels are regulated by the sympathetic nervous system.
- To determine if adrenergic agents affect ocular melatonin levels in rabbits and chickens.
Main Methods:
- Topical application of L-timolol, norepinephrine, forskolin, domperidone, and pilocarpine to rabbit and chicken eyes.
- Measurement of melatonin levels in ocular tissues (iris-ciliary body, iris, ciliary body).
- Assessment of N-acetyltransferase activity and effects of chemical sympathectomy using 6-hydroxydopamine.
Main Results:
- None of the tested drugs altered melatonin levels in rabbit or chicken ocular tissues.
- Topical forskolin did not affect N-acetyltransferase activity in the rabbit iris-ciliary body.
- Chemical sympathectomy did not alter nighttime ocular melatonin levels in rabbits or daytime levels in chickens.
Conclusions:
- Ocular melatonin levels do not appear to be solely regulated by the adrenergic sympathetic nervous system.
- The data suggest that a neurotransmitter other than norepinephrine regulates N-acetyltransferase activity and melatonin levels in the eye.