The role of nitric oxide in the electrical field stimulation-induced contractions of sphincter of oddi and gallbladder strips in Guinea pigs.
The aim of this study was to investigate the modulatory role of nitric oxide (NO) in the electrical field stimulation (EFS)-induced contractions of isolated sphincter of Oddi (SO) and gallbladder strips from guinea pigs. EFS was used to activate the intrinsic nerves in SO and gallbladder strips. EFS produced frequency-dependent biphasic contractile responses in the SO strips. A smaller contraction, "on response", occurred during EFS, which was followed by a bigger contraction, "off response". Both responses were completely and irreversibly abolished by tetrodotoxin (TTX) (10(-6) M). Atropine (10(-6) M) inhibited the "on response", but not the "off response". EFS produced frequency-dependent monophasic contractile responses in gallbladder strips, which were completely and irreversibly abolished by TTX (10(-6) M) and atropine (10(-6) M). A nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine (10(-4) M and 3 x 10(-4) M, in SO and gallbladder strips, respectively), significantly increased all EFS-induced contractions of SO and gallbladder strips. L-Arginine, but not D-arginine reversed the effect induced by the NOS inhibitor, at all frequencies, in both strips. These results suggested that NO released from nitrergic nerve endings might play a regulatory role in the cholinergic neurotransmission of guinea pig SO and gallbladder strips. The "off response" in he SO preparations might be a rebound increase that was modulated by the nonadrenergic, noncholinergic inhibitory mediator NO.
Gultekin
Hulya
H
Department of Pharmacology, Faculty of Medicine, Erciyes University, Turkey.
Erdem
S Remzi
SR
Emre-Aydingoz
Selda
S
Tuncer
Meral
M
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005704:Gallbladder / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D026602:Nitrergic Neurons / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D009803:Sphincter of Oddi / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D013779:Tetrodotoxin; D001285:Atropine; D001120:Arginine; D019001:Nitric Oxide Synthase