Two types of vasodilatation in cat choroid elicited by electrical stimulation of the short ciliary nerve.
Choroidal blood vessels are innervated by three types of vasoactive nerve fibers: sympathetic, parasympathetic and sensory fibers in the short ciliary nerve. We investigated whether or not stimulation of the short ciliary nerve elicits vasodilatation. In 30 cats (2-4 kg) anesthetized with pentobarbital sodium (30 mg kg-1, i.v.) and artificially ventilated (pancuronium bromide; 0.2 mg kg-1 hr-1, i.v.), choroidal blood flow was continuously measured trans-sclerally with a laser Doppler flowmeter. The lateral short ciliary nerve was stimulated electrically (0-50 V, 2 msec, 20 Hz, for 10 sec) at two sites, one close to the eyeball (site P) and the other between the main and accessory ciliary ganglia (site Q). Choroidal vasodilatation occurred with a high incidence (80%) in response to electrical stimulation of the short ciliary nerve at site P or Q, when cats had been treated with the alpha-adrenergic blocking agent phentolamine (3 mg kg-1) 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 abolished 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 (3 mg kg-1, i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)
Nakanome
Y
Y
Department of Ophthalmology, Tohoku University School of Medicine, Sendai, Japan.
Karita
K
K
Izumi
H
H
Tamai
M
M
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001783:Blood Flow Velocity; D002211:Capsaicin / Q000494:pharmacology; D002415:Cats; D002829:Choroid / Q000098:blood supply* / Q000294:innervation; D004558:Electric Stimulation; D018738:Hexamethonium / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D018738:Hexamethonium; D002211:Capsaicin