• The Korean Journal of Physiology and Pharmacology
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• 제13권6호
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• pp.503-510
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• 2009

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 $(10\;{\mu}M)$ 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 $(1\;{\mu}M)$, 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 $VDCC_L$.

• The Korean Journal of Physiology and Pharmacology
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• 제1권3호
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• pp.303-313
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• 1997

The role of the lower esophageal sphincter(LES) is characterized by the ability to maintain tone and to relax allowing the passage of a bolus. It is known that LES relaxation during swallowing may be induced by the cessation of the tonic neural excitation and the activation of non-adrenergic, non-cholinergic(NANC) inhibitory neurons. Furthermore, it is generally accepted that the relaxation of the smooth muscle is mediated primarily by the elaboration of adenosine 3',5'-cyclic monophosphate(cyclic AMP) and guanosine 3',5'-cyclic mono-phosphate(cyclic GMP) via activation of adenylate cyclase and guanylate cyclase, respectively. It is thus possible that cyclic nucleotides might be a second messenger involved in neural stimulation-induced relaxation of LES, although a relationship between relaxation and changes in cyclic nucleotides after neural stimulation has not been established. The present study was performed to define the participation of cyclic nucleotides in the relaxation of LES of dog in response to neural stimulation. Electrical field stimulation(EFS) caused relaxation of the canine isolated LES strips in a frequency-dependent manner, which was eliminated by pretreatment with tetrodotoxin$(1{\mu}M)$, but not by atropine$(100{\mu}M)$, guanethidine$(100{\mu}M)$ and indomethacin$(10{\mu}M)$. The nitric oxide synthase inhibitors, $N^G-nitro-L-arginine$, $N^G-nitro-L-arginine$ methyl ester and $N^G-monomethyl-L-arginine$ inhibited EFS-induced relaxation. Additions of sodium nitroprusside, a nitrovasodilator and forskolin, a direct adenylate cyclase stimulant, caused a dose-dependent relaxation of LES smooth muscle. Effects of sodium nitroprusside and forskolin were selectively blocked by the corresponding inhibitors, methylene blue for guanylate cyclase and N-ethylmaleimide(NEM) for adenylate cyclase, respectively. Dibutyryl cyclic AMP and dibutyryl cyclic GMP caused a concentration-dependent relaxation of the LES smooth muscle tone, which was not blocked by NEM or methylene blue, respectively. However, both NEM and methylene blue caused significant antagonism of the relaxation in LES tone in response to EFS. EFS increased the tissue cyclic GMP content by 124%, whereas it did not affect the tissue level of cyclic AMP. Based on these results, it is suggested that one of the components of canine LES smooth muscle relaxation in response to neural stimulation is mediated by an increase of cyclic GMP via the activation of guanylate cyclase. Additionally, an activation of cyclic AMP generation system was, in part, involved in the EFS-induced relaxation.

• 동의생리병리학회지
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• 제27권5호
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• pp.625-630
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• 2013

Erectile dysfunction (ED) is a highly prevalent disorder that affects millions of men worldwide. ED is now considered an early manifestation of atherosclerosis, and consequently, a precursor of systemic vascular disease. Lycii fructus extracts (LFE) were administered for 4 weeks to assess the improving effects on ED. Animals were divided into one normal group and four LFE-treated groups (0, 0.3, 0.6, and 1.2 g/kg). We induced ED in the study animals by oral administration of 20% ethanol instead of water everyday for 4 weeks. This study was designed to investigate the effects of LFE on the mRNA levels of inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) expression; NO levels of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP); blood profile; and erectile response of the corpus cavernosum of the rat penis. The libido of the LFE-administered male rats was higher than that of the ethanol control group. The erectile response of the corpus cavernosum was restored after LFE administration, to a level similar to the normal group. In addition, the iNOS in the corpus cavernosum of the male rats administered LFE decreased. In contrast, compared to the control group, LFE-administered male rats showed increased eNOS, NO and cGMP levels in the corpus cavernosum. These results indicate that LFE effectively restored ethanol-induced ED in male rats.

• 동의생리병리학회지
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• 제21권5호
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• pp.1271-1277
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• 2007

This study was designed to investigate the effects of Sagunja-tang Extract & Zingiberis rhizoma recens Juice (SEZJ) and Zingiberis rhizoma recens Juice (ZRJ) on the changes in regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP) in normal rats. The results were as follows ; SEZJ and ZRJ significantly increased rCBF in a dose-dependent manner, while it did not change MABP. This results suggest that SEZJ and ZRJ significantly increased rCBF by dilating pial arterial diameter. Increase of SEZJ-induced rCBF was significantly inhibited by pretreatment with methylene blue (10 ${\mu}g/kg$, i.p.), an inhibitor of guanylate cyclase, and indomethacin (1 mg/kg, i.p.), an inhibitor of cyclooxygenase. SEZJ-induced MABP was significantly increased by pretreatment with indomethacin but was not changed by methylene blue. These results suggested that the action of SEZJ was mediated by cyclic 3',5'-guanosine monophosphate.

• Journal of Ginseng Research
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• 제39권2호
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• pp.169-177
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• 2015

Background: Ginsenoside Rd (GSRd), one of the most abundant ingredients of Panax ginseng, protects the heart via multiple mechanisms including the inhibition of $Ca^{2+}$ influx.We intended to explore the effects of GSRd on L-type $Ca^{2+}$ current ($I_{Ca,L}$) and define the mechanism of the suppression of $I_{Ca,L}$ by GSRd. Methods: Perforated-patch recording and whole-cell voltage clamp techniques were applied in isolated rat ventricular myocytes. Results: (1) GSRd reduced $I_{Ca,L}$ peak amplitude in a concentration-dependent manner [half-maximal inhibitory concentration $(IC_{50})=32.4{\pm}7.1{\mu}mol/L$] and up-shifted the current-voltage (I-V) curve. (2) GSRd ($30{\mu}mol/L$) significantly changed the steady-state activation curve of $I_{Ca,L}$ ($V_{0.5}:-19.12{\pm}0.68$ vs. $-6.26{\pm}0.38mV$; n = 5, p < 0.05) and slowed down the recovery of $I_{Ca,L}$ from inactivation [the time content (${\zeta}$) from 91 ms to 136 ms, n = 5, p < 0.01]. (3) A more significant inhibitive effect of GSRd ($100{\mu}mol/L$) was identified in perforated-patch recording when compared with whole-cell recording [$65.7{\pm}3.2%$ (n = 10) vs. $31.4{\pm}5.2%$ (n = 5), p < 0.01]. (4) Pertussis toxin ($G_i$ protein inhibitor) completely abolished the $I_{Ca,L}$ inhibition induced by GSRd. There was a significant difference in inhibition potency between the two cyclic adenosine monophosphate elevating agents (isoprenaline and forskolin) prestimulation [$55{\pm}7.8%$ (n = 5) vs. $17.2{\pm}3.5%$ (n = 5), p < 0.01]. (5) 1H-[1,2,4]Oxadiazolo[4,3-a]-quinoxalin-1-one (a guanylate cyclase inhibitor) and N-acetyl-$\small{L}$-cysteine (a nitric oxide scavenger) partly recovered the $I_{Ca,L}$ inhibition induced by GSRd. (6) Phorbol-12-myristate-13-acetate (a protein kinase C activator) and GF109203X (a protein kinase C inhibitor) did not contribute to the inhibition of GSRd. Conclusion: These findings suggest that GSRd could inhibit $I_{Ca,L}$ through pertussis toxin-sensitive G protein ($G_i$) and a nitric oxide-cyclic guanosine monophosphate-dependent mechanism.

• The Korean Journal of Physiology and Pharmacology
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• 제10권6호
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• pp.337-341
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• 2006

The present study was designed to investigate the protein expression of nitric oxide synthase (NOS) and guanylyl cyclase (GC) activity in ischemia/perfusion (I/R) renal injury in rats. Renal I/R injury was experimentally induced by clamping the both renal pedicle for 40 min in Sprague-Dawley male rats. The renal expression of NOS isoforms was determined by Western blot analysis, and the activity of guanylyl cyclase was determined by the amount of guanosine 3', 5'-cyclic monophosphate (cGMP) formed in response to sodium nitroprusside (SNP), NO donor. I/R injury resulted in renal failure associated with decreased urine osmolality. The expression of inducible NOS (iNOS) was increased in I/R injury rats compared with controls, while endothelial NOS (eNOS) and neuronal NOS (nNOS) expression was decreased. The urinary excretion of NO metabolites was decreased in I/R injury rats. The cGMP production provoked by SNP was decreased in the papilla, but not in glomerulus. These results indicate an altered regulation of NOS expression and guanylyl cyclase activity in I/R-induced nephropathy.

• 대한수의학회지
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• 제40권4호
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• pp.691-699
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• 2000

We investigated the effects of nitric oxide (NO) donors, S-nitroso-L-cysteine (Cys-NO) and 3-morpholinosydnonimine hydrochloride (SIN-1), on the contractile and electrical activity of the circular muscle of guinea pig gastric antrum by using intracellular microelectrode technique. The gastric antral circular muscle showed spontaneous phasic contraction and slow wave of membrane potential. Cys-NO ($0.001{\sim}10{\mu}M$) and SIN-1 ($0.001{\sim}100{\mu}M$) reduced not only the tonic and phasic contraction but also the amplitude of slow wave in a concentration dependent manner. NO donors were more potent to inhibit phasic contraction than to do slow wave. These inhibitory effects of NO donors were mimicked by the membrane permeable guanosine-3',5'-cyclic monophosphate (cGMP) analogue, 8-bromo-cyclic GMP (8-br-cGMP, $10{\sim}300{\mu}M$). The inhibitory effects of SIN-1 and Cys-NO were antagonized by the guanylate cyclase inhibitor, 1H[ [1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, $10{\mu}M$). These results suggest that the inhibitory effects of NO donors on the mechanical and electrical activity is mainly mediated by cGMP pathway.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1993년도 학술대회지
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• pp.40-48
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• 1993

Intravenous administration of saponin extracted from the root of Panax ginseng lowered the blood pressure dose-dependently (10-200 mg/kg, B.W) in anesthetized rats. Therefore, experiments were designed to study the hypothesis that the lowering of blood pressure is associated with the release of endothelium-derived relaxing factor and the accumulation of guanosine 3, 5-cyclic monophosphate (cGMP). Rings of thoracic aorta with and without endothelium were suspended for the measurement of isometric tension in organ chamber and the tissue content of cGMP was measured by radioimmunoassay. All experiments were performed in the presence of $indomethacin(10^{-5}M).$ Ginseng saponin $(10^{-5}-3{\times}10^{-6}g/ml)$ relaxed contractions induced by phenylephrine $10^{-6}M)$ in the aorta with endothelium but not in that without endothelium. Treatment of aortic rings with $N^G$ monomethyl-L-arginine (L-NMMA, $10^{-4}M$ for 30 min), a competitive inhibitor of nitric oxide synthase, and methylene blue $(MB,\;3{\times}10^{-7}M$ for 30 min). an inhibitor of soluble guanylate cyclase, diminished the relaxation induced by Ginseng saponin. Ginseng saponin $10^{-4}g/ml$ for 2 min) increased the accumulation of cGMP in rings with endothelium. L-NMMA and MB inhibited the accumulation of cGMP induced by Ginseng saponin. These data suggest that vascular relaxations induced by Ginseng saponin are mediated by release of endothelium-derived relaxing factor and the accumulation of cGMP. The effect of Ginseng saponin on endothelial function in hypercholesterolemic rabbits was examined. In hypercholesterolemic rabbits fed with $2\%$ cholesterol for 8 weeks, relaxation of aortic rings to acetylcholine was impaired. The impaired relaxations of aortic rings in hypercholesterolemic rabbits were improved by dietary supplementation of Ginseng saponin, probably because of an improved release of endothelium - derived relaxing factor.

• 대한수의학회지
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• 제44권3호
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• pp.389-397
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• 2004

The therapeutic efficacy of xylamine in the field of psychological medicine has been recognized for years and the drug is used to treat depression and some other conditions, but little is known about its mechanism of action on vascular system. Therefore, the present study was designed to investigate the influence of xylamine on the contractile responses of isolated rat thoracic arteries to phenylephrine(PE) and potassium chloride(KCl). Xylamine produced a concentration-dependent relaxation in PE-precontracted endothelium intact(+E) rat aortic rings, but not in a KCl-precontracted aortic rings. Also, xylamine inhibited the PE-induced contraction in concentration-dependent manner, but not in the high KCl-induced contraction in +E rings. This concentration-dependent inhibition was suppressed by the removal of the endothelium (-E). The inhibitory effects of xylamine($0.3{\mu}M$) on the PE-induced contractions were suppressed by N(G)-nitro-L-arginine(L-NNA), N(omega)-nitro-L-arginine methyl ester(L-NAME), aminoguanidine, dexamethasone, methylene blue, 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one(ODQ), indomethacin, ryanodine, tetrabutylammonium(TBA), lidocaine, procaine and 0 mM extracellular $Na^+$, but not by 2-nitro-4-carboxyphenyl-n,n-diphenylcarbamate(NCDC), lithium, nifedipine, verapamil, 0 mM extracellular $Ca^{2+}$, glibenclamide and clotrimazole. These findings suggest that xylamine could act as a vasorelaxant and direct inhibitor of arterial contraction. This vasorelaxation involves an endothelial nitric oxide (NO)/cGMP (guanosine 3',5'-cyclic monophosphate) pathway or cyclooxygenase system, and an interference with $Ca^{2+}$ release, TBA-sensitive $Ca^{2+}$-activated $K^+$ channels and $Na^+$$ channels.

• 약학회지
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• 제41권3호
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• pp.370-380
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• 1997

The role of nitric oxide (NO) on the non-adrenergic non-cholinergic (NANC) relaxations induced by the short and prolonged electrical field stimulation (EFS) has been studied in the rabbit corpus cavernosum. In the presence of atropine and guanethidine the prolonged EFS (2-16 Hz) of corpus cavernosal strips precontracted with phenylephrine produced frequency-dependent relaxations, which were abolished by tetrodotoxin as shown in the relaxations induced gy the short EFS, indicating that their orgin is NANC nerve stimulation. $N^G$-nitro-L-arginine (L-NNA), inhibitor of nitirc oxide synthase, caused a concentration-dependent inhibition to the NANC relaxation, and at 100 M L-NNA the relaxation were virtually abolished. The inhibitory effect of L-NNA was reversed by L-arginine. Hemoglobin abolished the relaxations to NO and also caused a concentration-dependent inhibition of the NANC relaxation. The hemoglobin-resistant relaxation induced by EFS was eliminated by L-NNA. Methylene blue significantly reduced the NANC relaxation in a conentration-dependent manner. The NANC relaxation was not affected by a VIP-inactivating pepridase, alpha0chymotrypsin, whereas VIP-induced relaxation was completely abolished. NO- and VIP-induced relaxation were not affected by L-NNA. These results indicate that the NANC relaxation induced by prolonged EFS of the rabbit corpus cavernosum is mediated by NO-guanosine 3',5'-cyclic monophosphate pathway as shown in the relaxation induced by the short EFS, and that VIP release is not essential for the NANC relaxation of the rabbit corpus cavernosum and VIP is not involved the generation fo NO.