ABSTRACT
BACKGROUND: Taraxacum officinale (TO) is a traditional herbal medicine that has been widely used for abdominal illnesses. However, the efficacy and the mechanism of TO on gastric emptying (GE) and smooth muscle motility are unknown. METHODS: Ethyl acetate fraction (EA), n-butanol fraction (BF), and aqueous fraction (AF) were prepared in succession from 70% ethanol extract (EE) of TO using solvent polarity chromatography. Phenol red meal was adopted to estimate GE in mice. A polygraph was used to measure the smooth muscle motility in rats. KEY RESULTS: The percentage of GE was 48.8 ± 6.1% (vehicle control), 75.3 ± 6.5% (cisapride positive control), 68.0±6.7% (EE), 53.3±6.0% (EA), 54.1±6.3% (AF), and 86.0±6.5% (BF). Thus, BF was determined to be most effective in accelerating GE. This stimulatory effect of BF on GE was also supported by the observation that BF increased spontaneous contraction of gastric fundus and antrum and decreased the spontaneous motility of pyloric sphincter in vitro. Atropine blocked the stimulatory effect of BF on GE, whereas phentolamine and propranolol had no effect. CONCLUSIONS & INFERENCES: BF seems to be a promising prokinetic agent. BF-induced increase in the contraction of fundus and antrum contributes to an increase in the intra-gastric pressure. BF-induced decrease in the motility of pyloric sphincter contributes to a decrease in the resistance of food from the stomach to the small intestine. The acceleration of GE by BF is likely to be exerted through cholinergic stimulation.
Subject(s)
Gastric Emptying/drug effects , Gastrointestinal Motility/drug effects , Plant Extracts/pharmacology , Rodentia , Taraxacum/chemistry , 1-Butanol/pharmacology , Adrenergic alpha-Antagonists/pharmacology , Animals , Atropine/pharmacology , Cisapride/pharmacology , Dose-Response Relationship, Drug , Gastrointestinal Agents/pharmacology , Male , Mice , Mice, Inbred BALB C , Muscle Contraction/drug effects , Muscle, Smooth/drug effects , Muscle, Smooth/physiology , Parasympatholytics/pharmacology , Phentolamine/pharmacology , Pyloric Antrum/drug effects , Pyloric Antrum/physiology , Pylorus/drug effects , Random Allocation , Rats , Rats, WistarABSTRACT
In our study of the effects of hyposmotic swelling on the Ca(2+)-activated potassium currents [I(K(Ca))] and its mechanism, we employed the whole-cell patch clamp technique using the gastric antral circular myocytes of the guinea-pig. Hyposmotic swelling efficiently increased I(K(Ca)), and the extent of changes in I(K(Ca)) was sharply dependent on the osmolarity of the perfusion solutions. When the calcium-free solution (EGTA 10 microM added in calcium-free solution) was superfused, I(K(Ca)) was not increased by the hyposmotic swelling. Gadolinium (Gd(3+)) 100 nM, a blocker of the stretch-activated nonselective cation channel, blocked the activation of I(K(Ca)) induced by hyposmotic swelling, but nicardipine 5 microM (the L-type calcium channel blocker) did not. Heparin 3 mg/ml, a potent inhibitor of inositol triphosphate receptor (InsP(3)R), did not inhibit the response, and caffeine 1 mM (the agonist for calcium-induced calcium release [CICR]) imitated the effect of hyposmotic swelling. Ryanodine (15 microM), markedly inhibited the effect. These results suggest that hyposmotic swelling activates I(K(Ca)), and the activation is associated with CICR, which is triggered by extracellular calcium influx through the stretch-activated channel (SA channel).
Subject(s)
Muscle, Smooth/physiology , Myocardium/cytology , Potassium Channels/physiology , Stomach/physiology , Animals , Caffeine/pharmacology , Calcium Channel Blockers/pharmacology , Central Nervous System Stimulants/pharmacology , Female , Gadolinium/pharmacology , Guinea Pigs , Male , Nicardipine/pharmacology , Osmotic Pressure , Patch-Clamp Techniques , Pyloric Antrum/cytology , Pyloric Antrum/physiology , Ryanodine/pharmacologyABSTRACT
AIM: To study the effect of exogenous nitric oxide (NO) on electric and mechanical activities of gastric antral circular muscle in guinea pigs in vitro. METHODS: Mechanical and electric activities of gastric antral circular muscle in guinea pigs were recorded simultaneously. RESULTS: Sodium nitroprusside (SNP, 0.5 mumol.L-1), an NO donor, inhibited the frequency and amplitude of fast wave and spontaneous contraction of the strips (P < 0.01). SNP-induced inhibition was not blocked by tetrodotoxin, atropine, phentolamine, and propranolol (P > 0.05), but diminished by methylene blue (P < 0.01) and oxyhemoglobin (P < 0.01). CONCLUSION: Exogenous NO inhibits gastric antral myoelectric and mechanical activities in guinea pigs. The inhibitions are produced by NO acting on extracellular membrane and enhancing the level of cGMP.
