Relaxation patterns of human gastric corporal smooth muscle by cyclic nucleotides producing agents.
To elucidate the mechanism of cyclic nucleotides, such as adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5' -cyclic monophosphate (cGMP), in the regulation of human gastric motility, we examined the effects of forskolin (FSK), isoproterenol (ISO) and sodium nitroprusside (SNP) on the spontaneous, high K(+) and acetylcholine (ACh)-induced contractions of corporal circular smooth muscle in human stomach. Gastric circular smooth muscle showed regular spontaneous contraction, and FSK, ISO and SNP inhibited its phasic contraction and basal tone in a concentration-dependent manner. High K(+) (50 mM) produced sustained tonic contraction, and ACh (10 microM) produced initial transient contraction followed by later sustained tonic contraction with superimposed phasic contractions. FSK, ISO and SNP inhibited high K(+)-induced tonic contraction and also ACh-induced phasic and tonic contraction in a reversible manner. Nifedipine (1 microM), inhibitor of voltage-dependent L-type calcium current (VDCC(L)), almost abolished ACh-induced phasic contractions. These findings suggest that FSK, ISO and SNP, which are known cyclic nucleotide stimulators, inhibit smooth muscle contraction in human stomach partly via inhibition of VDCC(L).
Kim
Young Chul
YC
Department of Physiology, Chungbuk National University College of Medicine, Cheongju 361-763, Korea.
Choi
Woong
W
Sung
Rohyun
R
Kim
Heon
H
You
Ra Young
RY
Park
Seon-Mee
SM
Youn
Sei Jin
SJ
Kim
Mi-Jung
MJ
Song
Young-Jin
YJ
Xu
Wen-Xie
WX
Lee
Sang Jin
SJ
Yun
Hyo-Yung
HY