The results shown in the text and figures are expressed as
mean ± SEM. Statistical analyses were made using the Student’s
paired and unpaired t-tests for two groups and the Tukey’s
test after one-way ANOVA for more than three groups. Drugs used were l-arginine, hexamethonium bromide (Nacalai
Tesque, Kyoto, Japan), atropine sulfate (Tanabe Seiyaku, Osaka, Japan),α
,β-methylene ATP, physostigmine sulfate, aminophylline, suramin
sodium salt (Sigma), timolol maleate (Banyu, Tokyo, Japan),
tetrodotoxin (Sankyo, Tokyo, Japan), prazosin hydrochloride (Wako Pure
Chemical Industries, Osaka, Japan), PG F2α (Pharmacia Upjohn, Tokyo, Japan), N G-nitro-l-arginine
(L-NA), N G-nitro-d-arginine
(D-NA), neuropeptide Y (Peptide Institute, Osaka, Japan), acetylcholine
chloride (Daiichi, Tokyo, Japan), BIBP3226[
R-N2-(diphenylacetyl)-N-(4-hydroxyphenyl)methyl-argininamide]
(Peninsula Laboratory, Belmont, CA); and papaverine hydrochloride
(Dainippon Pharmaceutical, Osaka, Japan). ODQ,
1H[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, was kindly provided
by Salvador Moncada.