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Abstract #12115 Published in IGR 7-1
Time course of changes in optic nerve head circulation after acute reduction in intraocular pressure
Takayama J; Tomidokoro AInvestigative Ophthalmology and Visual Science 2005; 46: 1409-1419
See also comment(s) by Douglas Anderson •
PURPOSE: To study the time course of changes in circulation in the optic nerve head (ONH) after acute reduction in intraocular pressure (IOP) and to evaluate the effects of a calcium antagonist, a nitric oxide synthetase (NOS) inhibitor, indomethacin, and sympathetic nerve amputation on the changes in ONH circulation after reduction of IOP. METHODS: In anesthetized albino rabbits, acute reduction of IOP (acute increase in ocular perfusion pressure [OPP]) was manometrically achieved and normalized blur (NB), a quantitative index of tissue blood velocity obtained with the laser speckle method, was serially monitored for 30 seconds and 60 minutes. The effects of systemic administration of 1 mug/kg per hour nilvadipine (a calcium antagonist), 300 μg/kg Nomega-nitro-l-arginine (l-NAME, a nonselective NOS inhibitor), and 5 mg/kg indomethacin or sympathetic nerve amputation on the changes in NB after reduction of IOP were studied. RESULTS: During changes in IOP from 10 to 40 mmHg and then back to 10 mmHg, NB exhibited no significant change. During changes in IOP from 10 to 60 mmHg and then back to 10 mmHg, NB initially decreased with an increase in IOP to 60 mmHg and then increased to baseline level when IOP was returned to 10 mmHg. In the nilvadipine-treated rabbits, during changes in IOP from 10 to 40 mmHg and back to 10 mmHg and during the changes from 10 to 60 mmHg and back to 10 mmHg, NB decreased with increase in IOP to 40 or 60 mmHg and then increased to slightly above the baseline when IOP returned to 10 mmHg. l-NAME, indomethacin, and sympathetic nerve amputation each had little effect on the time course of change in NB. CONCLUSIONS: ONH circulation was stably maintained after reduction of IOP from 40 to 10 mmHg but not after that from 60 to 10 mmHg. The changes in NB after reduction of IOP occurred quickly and were partially impaired with a calcium antagonist, but not with the NOS inhibitor, indomethacin, or sympathetic nerve amputation. These findings suggest the importance of vascular smooth muscle in maintaining stable ONH circulation against reduction of IOP in a fashion nearly independent of NO, endogenous prostaglandins, and the sympathetic nervous system.
Dr. J. Takayama, Eye Clinic, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan
Classification:
6.11 Bloodflow measurements (Part of: 6 Clinical examination methods)
5 Experimental glaucoma; animal models
