Isolated Dog Ophthalmic Arteries

Methods. Changes in isometric tension were recorded in helical strips of the arteries, and the presence of perivascular nerve containing NADPH diaphorase was histochemically demonstrated. Results. Nicotine (10~ M, EOA and IOA) and transmural electrical stimulation (5 Hz, EOA) produced a slight or no contraction followed by a moderate relaxation in the strips contracted with prostaglandin F2a. The contraction was abolished by a-adrenoceptor antagonists. The relaxation was abolished and the contraction was potentiated by N-nitro-L-arginine (L-NA), a nitric oxide (NO) synthase inhibitor; the relaxation was reversed by L-arginine. Contractile response in L-NA-treated EOA was greater than in the IOA, and the relaxation was less in nontreated EOA. NO-induced relaxation and norepinephrine-induced contraction were not influenced by L-NA. There were plenty of nerve fibers visualized by NADPH diaphorase staining method in the adventitia of EOA and IOA, indicating the presence of NO synthasecontaining nerves.