Monkey central retinal artery is innervated by nitroxidergic vasodilator nerves.
OBJECTIVE
To determine whether the monkey central retinal artery is innervated by vasodilator nerves and to analyze the mechanism underlying the neurogenic response.


METHODS
Changes in isometric tension were recorded in helical strips of the arteries, which were stimulated by transmurally applied electrical pulses or nicotine. The presence of perivascular nerve fibers containing nitric oxide (NO) synthase immunoreactivity was determined histologically.


RESULTS
Transmural electrical stimulation (5 Hz) and nicotine produced a relaxation of the arterial strips denuded of the endothelium, treated with prazosin, and contracted with prostaglandin F2 alpha. The response was not influenced by timolol, atropine, and indomethacin, but it was abolished by methylene blue and oxyhemoglobin. NG-nitro-L-arginine, a NO synthase inhibitor, abolished the neurogenic relaxation, and L-arginine restored the response. Antagonists of calcitonin gene-related peptide and vasoactive intestinal polypeptide in sufficient concentrations did not influence the response to nerve stimulation by nicotine. There were abundant nerve fibers and bundles containing NO synthase immunoreactivity in the adventitia.


CONCLUSIONS
Monkey central retinal arteries are innervated by NO synthase-containing nerves that liberate NO possibly as a neurotransmitter on excitation to produce muscular relaxation.
Toda
N
N
Department of Pharmacology, Shiga University of Medical Science, Ohtsu, Japan.
Toda
M
M
Ayajiki
K
K
Okamura
T
T
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D004396:Coloring Agents / Q000494:pharmacology; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005731:Ganglionic Stimulants / Q000494:pharmacology; D007124:Immunoenzyme Techniques; D007537:Isometric Contraction; D008251:Macaca; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000294:innervation*; D009411:Nerve Endings / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D010108:Oxyhemoglobins / Q000494:pharmacology; D012161:Retinal Artery / Q000294:innervation*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D004396:Coloring Agents; D004791:Enzyme Inhibitors; D005731:Ganglionic Stimulants; D010108:Oxyhemoglobins; D019335:Nitroarginine; D009569:Nitric Oxide; D009538:Nicotine; D019001:Nitric Oxide Synthase; D015740:Calcitonin Gene-Related Peptide; D008751:Methylene Blue