Dexmendetomidine decreases spontaneous contraction of duodenal smooth muscle of rabbits in vitro / 中国药理学通报

Aim To observe the influences of dexmen-detomidine on the spontaneous contraction of duodenal smooth muscle of rabbits in vitro and explore the mech-anisms.Methods The rabbits ( male or female ) were stunned and the duodenums were isolated .The sam-ples of duodenal segments were connected with tension transducer , which were then put into oxygen saturation Krebs-Henseleit ( K-H) solution .The influences of dex-mendetomidine on amplitude ( AM ) and frequency ( FR ) of duodenal smooth muscle were recorded by BL-420 F biological signal processing system .The cu-mulative dosing method was used to observe the differ-ent concentrations of dexmedetomidine on duodenal smooth muscle spontaneous contraction .Glibenclamide ( Gli) was added to K-H solution before dexmendeto-midine.In the calcium-free K-H solution, calcium chloride and rynodine were added before dexmendeto-midine.The mechanisms of dexmendetomidine were studied .Results ① Dexmendetomidine reduced the amplitude of spontaneous contraction of duodenal smooth muscle in rabbits in a dose-dependent manner ( P0.05 ) .② Gli ( P <0.05 ) partly abolished the inhibitory effects of dexmendetomi-dine on duodenal smooth muscle .③ Dexmendetomi-dine inhibited the contraction of duodenum smooth muscle induced by calcium chloride ( P <0.05 ) and rynodine ( P<0.05 ) application into calcium-free K-H solution.Conclusion Dexmendetomidine inhibits the spontaneous contraction of duodenal smooth muscle of rabbits in vitro.The mechanisms may be related to ac-tivating ATP sensitive potassium channels , inhibition of the extracellular calcium influx via cell membrane and intracellular calcium release via sarcoplasmic reticulum in duodenal smooth muscle .

Role of hyperpolarization-activated cyclic nucleotide-gated cation nonselective channel in spontaneous contrac-tion of smooth muscles in human isolated ureters / 局解手术学杂志

Objective To investigate effects of hyperpolarization-activated cyclic nucleotide-gated cation nonselective channel in the hu-man ureter on the spontaneous contraction of smooth muscles. Methods Four HCN subtypes were detected in human ureteral tissue using reverse transcription polymerase chain reaction,Western blotting and immunohistochemical. ZD7288,the HCN blocker, was used to observe the changes of ureteral muscle contraction amplitude and frequency by applying the ureteral smooth muscle strip test in vitro. Results HCN1-4 isoforms were all identified in human ureter using reverse transcription-polymerase chain reaction and Western blotting. Through the immunohistochemical,HCN channel was found mostly in the urothelium layer and muscular layer of human ureteral wall. ZD7288 significantly decreased the bladder excitation. Conclusion All 4 HCN channel hypotypes exist in the human ureter, and affect the ureteral excitation.

Spontaneous Contractions Augmented by Cholinergic and Adrenergic Systems in the Human Ureter

Interstitial cells of Cajal (ICC) evoke pacemaker activities in many tissues. The purpose of this study was to investigate the relationship between interstitial cell and pacemaker activity in the human ureter through the recording of spontaneous contractions. Spontaneous contractions of eight circular and longitudinal smooth muscle strips of the human ureter to acetylcholine (ACh) and/or norepinephrine (NE) were observed. Human ureteral strips were divided into proximal and distal groups, and each group was subdivided into circular and longitudinal groups. The proximal group showed spontaneous activities of 3~4 times within 5 minutes in the longitudinal group. ACh (10(-4) M) augmented the frequency of the spontaneous contractions. The cumulative application of NE also augmented the frequency in a dose-dependent manner. The effects of NE application were inhibited by concomitant application of 10(-5) M glibenclamide. Receptor tyrosine kinase (c-kit) staining revealed abundant ICCs only in proximal tissues. Therefore, spontaneous contractions of the human ureter might be modulated by ICC in the proximal region, and the actions might be related with the activation of cholinergic and/or adrenergic system mediated by a glibenclamide-sensitive pathway.

Inhibitory effect of Suaeda asparagoides (Miq.) extract on the motility of rat gastric antrum is mediated by beta-adrenoceptor / 한국실험동물학회지

Suaeda asparagoides (Miq.) has long been used as a Korean folk herbal medicine for the treatment of functional gastrointestinal disorders. However, reports on its pharmacological activity on gastrointestinal motility are scarce. The present study investigated the effects of Suaeda asparagoides water fraction of the extract (SAWF) on antral motility in vitro. Muscle strips from rat gastric antrum were set up in an organ bath in a circular orientation. SAWF (100 microg/mL) inhibited the spontaneous contraction of antral circular muscle strips. These inhibitory effects were not significantly affected by tetrodotoxin (1 microM), N omega-Nitro-L-arginine methyl ester hydrochloride (100 microM), 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (10 microM), ryanodine (10 microM) and phentolamine (10 microM). SAWF-induced inhibition was mostly restored by cyclopiazonic acid (10 microM). Furthermore, the beta-adrenergic receptor antagonist, propranolol (10 microM), abolished SAWF-induced inhibition. These results suggest that SAWF may exert its activity on gastrointestinal smooth muscle via a-adrenergic receptors and sarcoplasmic reticulum Ca2+ ATPase.

Effects of ryanodine receptor channels on the spontaneous contractions of detrusor in rats of detrusor instability / 第三军医大学学报

Objective To explore the myogenic basis of the increased excitability and contractile activity in detrusor instability (DI) and investigate the differences of spontaneous contractions by ryanodine receptor (RyR) channels regulation in sarcoplasmic reticulum (SR) between DI and normal bladder muscle and of the RyR channels protein expression. Methods DI model was confirmed by filling cystometry from rats that underwent partial bladder outlet obstruction (BOO) about 8 weeks ago. Muscle strips were dissected from fresh bladder under microscope and the isometric tension in DI and normal strips were detected. The contractions were recorded in these strips exposed to some agents. SR microsome protein was obtained from DI and normal bladder muscle preparations and was used for Western blot analysis to determinate RyR channels expression. Results Treated with RyR channels blocker ryanodine , the contractile frequence significantly increased in normal strips, but not in DI muscle. Western blot analysis showed that RyR channels expression in DI muscle was significantly less than that in normal preparations. Conclusion RyR channels act a negative role in spontaneous contractile activity and the presumed mechanism may involve in Ca 2+ release of RyR channels which causes activation of Ca 2+ -dependent K + channels to decrease contractility. But this crosstalk mechanism is weaken in DI muscle, which provides a chance for spontaneous contractile overactivity.

MOLYBDENUM AND SPONTANEOUS CONTRACTION OF CARDIAC CELLS IN VITRO / 营养学报

Cardiac cell was cultured in low (5%) and normal (20%) bovine serum medium with or without molybdenum (Mo) supplementation (0.7ppm). Spontaneous contraction of the cultured cells was examined periodically. It was observed that the spontaneous contraction of the cardiac cells cultured in the low serum medium was better than that in the same medium without Mo and the frequency of the contraction was almost near the one cultured in normal serum medium. Some strengthen effect of Mo on the contraction was also seen in cardiac cell cultured in the normal serum medium with Mo.It suggested that Mo was necessitated in the contraction of cardiac cell and might be involved with the pathogenesis of certain cardiac diseases and Keshan disease and with their prophylaxis and treatment as well.