[Experimental research on choroidal circulation. 2. Choroidal blood flow increase elicited by electrical stimulation of parasympathetic nerve behind the eyeball in the cat].

The present studies were performed to examine whether the nerves behind the eye ball contain parasympathetic fibers which dilate the choroidal blood vessels. Choroidal blood flow in the cat (20 animals) was measured trans-sclerally with a laser Doppler flowmeter. Cats were anesthetized with pentobarbital sodium (30 mg/kg, i.v.) and artificially respirated after injection of pancuronium bromide (0.2 mg/kg/hr, i.v.). Electrical stimulation of the short ciliary nerve as well as of the nerve between the ciliary ganglion and accessory ciliary ganglion, where the sensory nerve is absent, elicited an increase choroidal blood flow in an intensity-dependent manner. Application of capsaicin, which is known to desensitize the polymodal nociceptive C-fibers, to these nerves did not abolish the increase in blood flow in response to electrical stimulation of the short ciliary nerve. Atropine, a muscarinic receptor antagonist, and phentolamine, an alpha-adrenoceptor blocking agent, had no effect on these responses. The results suggest that the blood flow increase elicited by stimulation of these nerves is mediated via activation of the atropine-resistant parasympathetic vasodilator fibers supplying the choroid in the cat.