Jpn. J. Pharmacol. 82 (2), 164-167 (2000)

1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) Inhibits Cyclic
GMP-PKG Pathway-Independent Nonadrenergic, Noncholinergic
Relaxation in Longitudinal Muscle of the Rectum of Wistar-ST Rats

Masashi Nakagawa^1,2, Tadayoshi Takeuchi¹, Satomi Niioka¹, Michiru Yamaji¹,
Yutaka Okishio¹, Hideaki Nishio¹ and Fumiaki Hata^1,3,*


¹Departmentﾊof Veterinary Pharmacology, College of Agriculture and ³Department of Molecular Physiology and Biochemistry,
Research Institute for Advanced Science and Technology, Osaka Prefecture University, Sakai 599-8531, Japan
²Departmentﾊof Anesthesiology, Sakai Municipal Hospital, Sakai 590-0064, Japan
*ﾊTo whom correspondence should be addressed⁽¹⁾.

Abstract: Participation of the nitric oxide-cyclic GMP pathway in nonadrenergic, noncholinergic (NANC) relaxation induced by electrical field stimulation of longitudinal muscle of the rectum of Wistar-ST rats was studied by using a selective inhibitor of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). ODQ concentration dependently inhibited the relaxation and at 10ﾊmM, maximally inhibited it by 83%. However, results obtained with N^G-nitro-L-arginine, L-arginine and exogenously added nitric oxide excluded the participation of nitric oxide in the relaxation. An inhibitor of cyclic GMP-dependent protein kinase (PKG) partially (39%) inhibited the relaxation. ODQ also significantly inhibited the relaxation, which persisted after the PKG inhibitor-treatment, by 85%. The results strongly suggest that ODQ inhibits the NANC relaxation in a cyclic GMP-PKG pathway-independent manner.

Keywords: 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), Soluble guanylyl cyclase,
Nonadrenergic, noncholinergic (NANC) relaxation