Changes of large-conductance calcium-activated potassium channel in gastric smooth muscle cells of diabetic gastroparesis rats / 中国病理生理杂志

[ ABSTRACT] AIM: To discuss the relevance between the pathogenesis of diabetic gastroparesis and the large-conductance calcium-activated potassium channels ( BKCa ) in gastric smooth muscle cells.METHODS:The SD rats were randomly divided into control group and model group.The gastric smooth muscle cells of the SD rats were enzymatically iso-lated in a low calcium solution containing papain.The current was recorded by patch clamp single channel recording tech-nique.The expression of KCNMA and KCNMB1 were observed by the method of immunohistochemistry.RESULTS:The value of BKCa single channel conductance was (220.10 ±10.90) pS;the channels had distinct voltage dependent and cal-cium dependent characteristics.In outside-out patch (Vm =+30 mV), the activation of BKCa was blocked by 200 nmol/L IbTX completely.Compared with control group, the open probability and amplitude of current in model group significant-ly increased, while the mean open time and mean close time significantly decreased.Compared with control group, the ex-pression of KCNMB1 in model group was significantly increased.CONCLUSION: Up-regulation of β1-subunit and in-crease in BKCa functional activities may be associated with diabetes gastroparesis in rats.

The effect of hesperdin and synephrine on the isolated hastric smooth muscle cells / 中国药理学通报

Aim To study the effect of hesperdin and synephrine on the isolated gastric smooth muscle cells.Method Gain isolated gastric smooth muscle cells by digesting gastric smooth muscle with collagenase(typeⅡ), measure long axis length of 25～50 cells randomly under microscope. Then, compare the contraction change of cells between before and after given drugs, the contraction change of cells is expressed with percent, negative expresses contraction, positive expresses relaxation.Results Hesperdine had no effect on the isolated gastric smooth muscle cells. The contractile response to synephrine was prompt, rising to a peak within 60 s and dose-dependent at the range of 0.001～1 g?L -1. Synephrine inhibited the excited cells caused by acetylcholine(P

Effects of Folium Crataegi Water Extract on the Contractility of Isolated Gastric and Intestinal Muscle Strips in Rats / 中国药房

OBJECTIVE: To study the effects of Folium Crataegi water extract on contractility of isolated gastric and intestinal smooth muscle strips in rats. METHODS: The effects of Folium Crataegi water extract on the contractility of isolated rat gastric and intestinal smooth muscle strips in the presence of normal Krebs’ solution, acetylcholine or atropine were investigated. RESULTS:Folium Crataegi water extract (5～20 mg?mL-1)significantly enhanced the contractility of rat gastric and intestinal smooth muscle strips in a dose-dependent manner, and Folium Crataegi water extract (20 mg?mL-1) could enhance the intensive contraction induced by acetylcholine and antagonize the relaxation of intestinal smooth muscle induced by atropine. CONCLUSION:Folium Crataegi water extract has remarkable stimulation on the contractility of isolated rat gastric and intestinal smooth muscle strips.

Nitroxergic nerve relaxes rat gastric smooth muscle by NO-cGMP pathway

This study was undertaken to investigate an involvement of nitroxergic innervation in gastric smooth muscle of rat. Isometric tension study, the measurement of single cell length, NADPH diaphorase stain of smooth muscle layers and neuronal nitric oxide synthase (nNOS) western blotting were performed. Sodium nitroprusside (SNP), a nitric oxide donor, relaxed the muscle strips precontracted by acetylcholine (ACh) in a concentration-dependent manner. Pretreatment of L-arginine decreased the contraction induced by electric field stimulation (EFS). Pretreatment of NG-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, increased the EFS-induced contractions. LY 83583, a guanylate cyclase (GC) inhibitor, reversed the inhibitory actions of L-arginine on the muscle contractions. The effects of L-Arginine, L-NAME and LY 83583 on ACh-induced contractions were not significant. L-arginine reduced the EFS-induced contraction in circular muscle, whereas L-NAME enhanced the EFS-induced contraction in longitudinal strips. By EFS, the phasic contractions appeared approximately 20~25 seconds later. L-NAME significantly shortened the delay time to about 2~3 seconds. In single cell study, ACh contracted gastric smooth muscle cells, SNP relaxed the cells, and the latter also inhibited the ACh-induced contraction. LY 83583 enhanced the ACh-induced contraction and antagonized SNP-induced relaxation. NADPH diaphorase activity was assessed by a histochemistry, nitroblue tetrazolium (NTB) staining. Positive staining was observed in both circular and longitudinal muscle layers. L-arginine increased the staining, while L-NAME decreased the staining. Western blotting for nNOS proved the presence of nNOS in rat gastric smooth muscle. EFS and additional Ca2+ increased nNOS protein expression. These results suggest that in rat stomach, both circular and longitudinal muscle layers are innervated with nitroxergic nerves which relax the gastric smooth muscle via NO-cGMP pathway.

Effects of prostaglandin E2 on the spontaneous contractions and electrical activities of the antral circular muscle in guinea-pig stomach

The spontaneous contractions of gastric smooth muscles are regulated by slow waves, which are modulated by both nervous system and humoral agents. This study was designed to examine the effects of Prostaglandin E2 (PGE2) on the contractile and electrical activities of antral smooth muscles in guinea-pig stomach, using an intracellular recording technique. To elucidate the underlying mechanism for its effect on contractility, ionic currents were also measured using a whole-cell patch clamp method. The basal tone by PGE2 was variable, whereas the magnitude of phasic contractions was reduced (19.0 +/- 2.1%, n=19). The resting membrane potentials were hyperpolarized (-4.4+/-0.5 mV, n=10), and plateau potentials were lowered (-2.9+/-0.5 mV, n=10). In most cases, however, the initial peak potentials of slow waves were depolarized more by PGE2 than those of control. The frequency of the slows wave was increased from 5.7+/-0.2 cycles/min to 6.5+/-0.2 (n-22). Voltage-operated Ca2+ currents were decreased by PGE2 (n=5). Voltage-operated K+ currents, both Ca-dependent and Ca-independent, were increased (n-5). These results suggest that PGE2 plays an important role in the modulation of gastric smooth muscle activities, and its inhibitory effects on the contractility and activities of slow waves are resulted from both decrease of Ca2+ currents and increase of K+ currents.