1995 Fiscal Year Final Research Report Summary
OCULAR CIRCULATION AND INNERVATIO
| Project/Area Number |
06671747
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Ophthalmology
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
KARITA Keishiro TOHOKU UNIV., PHYSIOL., ASSOC.PROF., 歯学部, 助教授 (40004600)
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| Co-Investigator(Kenkyū-buntansha) |
IZUMI Hiroshi TOHOKU UNIV., PHYSIOL., TUTOR, 歯学部, 助手 (20108541)
TAMAI Makoto TOHOKU UNIV., OPHTHALMOL., PROF., 医学部, 教授 (90004720)
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| Project Period (FY) |
1994 – 1995
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| Keywords | choroidal blood flow / short ciliary nerve / antidromic vasodilatation / parasy mpathetic vasodilatation / capsaicin / cat |
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| Research Abstract |
Choroidal blood vessels are innerv ated by three types of vasoactive nerve fibers : sympathefic, parasy mpathetic and sensory fibers in the short ciliary nerve. We investigated whether or not stimulation of the short ciliary nerve elicits vasodilatation. In 30 cats (2-4kg) anesthetized with pentobarbital sodium (30mg/kg, iv) and artificially ventilated (pancuronium bromide ; 0.2mg/kg/hr, iv), choroidal blood flow was continuously measured trans-sclerally with a laser Doppler flowmeter. The lateral short ciliary nerve was stimul ated electrically (0-50V,2ms, 20Hz, 10s) at two sites, one close to the eyeball (site P) and the other between the main and accessory ciliary gandlia (site Q). Choroidal vasodilatation occurred with a high incidence (80%) in response to electrical sfimulafion of the short ciliary narve at site P or Q,when cats had been treated with the alpha-adrenergic blocking agent phentolamine 3mg/kg) to eliminate sympathetic vasoconstrictor effects. A long-lasting vasodilatation was observed during 1% capsaicin application to the nerve bundle at site P,but not at site Q and capsaicin nearly abolis hed the vasodilatation evoked by stimulation at site P,but not that evoked from site Q.Vasodilatation elicited by electrical stimulation at site P or Q was not sensitive to the ganglion-blocking agent hexamethonium (3mg/kg, iv). It is suggested that two different mechanisms underlay the evoked blood flow increases in the choroid : one is a capsaicin-sensitive vasodilatation induced by antidromic activation of sensory fibers and the other is a capsaicin-insensitive vasodilatation mediated by orthodromic activation of the post-ganglionic parasy mpathetic nerve fibers.
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