Animals ; In Vitro Techniques ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; physiology ; Progesterone ; pharmacology ; Rabbits ; Trachea ; drug effects

AIMIn order to elucidate the underlying mechanism of depressed maximal isometric twitch tension normalized by cross sectional area of muscle strip in unloaded soleus.

METHODSThe soleus and extensor digitorum longus (EDL) muscle strips were perfused in vitro and treated by 2,3-Butanedione monoxime (BDM).

RESULTSThe BDM decreased Pt of soleus and EDL in a concentration-dependent manner. The Pt could restored completely to normal level after washing out BDM. The isometric twitch duration was not altered during 1 mmol/L BDM of perfusion, but was shortened at 10 mmol/L dose. The time from maximal to half Pt in EDL was shorter than that in soleus during 10 mmol/L BDM of perfusion. The inhibitory effects of BDM on myosin ATPase activity were higher in EDL than in soleus. The inhibitory extent of BDM on myosin ATPase activity of soleus and EDL was lower than that on Pt.

CONCLUSIONThese results suggest that reduction in cross-bridge function of skeletal muscle may be one of reasons induced a decrease in its Pt. BDM is not a specific inhibitor on myosin ATPase activity and can affect multiple parts of excitation-contraction coupling in skeletal muscle.

Animals ; Diacetyl ; analogs & derivatives ; pharmacology ; Isometric Contraction ; drug effects ; physiology ; Male ; Muscle Contraction ; drug effects ; physiology ; Muscle, Skeletal ; drug effects ; physiology ; Myosins ; antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley

SS-cream (Severance Secret cream) is made up of extracts from 9 natural products for treating premature ejaculation (PE). SS-cream has been proved to be effective in the treatment of PE in pilot clinical studies. It has also been found to have a potentiating effect of their erectile capacity in some patients. Therefore, we investigated the pharmacological actions of SS-cream and the extracts of its individual components in rabbit corpus cavernosal smooth muscle to realize the effect of SS-cream on penile erection. Extracts of Bufonis Venenum induced a dose-related contraction of rabbit corpus cavernosal muscle, which was significantly inhibited by phentolamine. Extracts of Caryophylli Flos induced a dose-related relaxation in the muscle strips precontracted with phenylephrine (5 x 10(-6)M; PHE). Caryophylli Flos caused a dose-dependent inhibition of the PHE induced contraction and also inhibited the contractility of Bufonis Venenum. Other extracts, when used individually or in a mixture, induced a dose-related relaxation in the precontracted muscle strips with PHE. SS-cream began to exert a relaxing effect at the concentration of 0.05 mg/ml in the muscle strips precontracted muscle strips with PHE (5 x 10(-6)M); causing dose-dependent relaxation with a maximal effect at 0.2 mg/ml. The relaxation effect of SS-cream was partially inhibited by endothelial disruption and by pretreatment with methylene blue, pyrogallol, atropine, and indomethacin, although they were not statistically significant. The results show that SS-cream has a relaxing effect on cavernosal smooth muscle. And it is partly related with enhancing the NO/cyclic GMP pathway although the relaxation mechanism in detail remains to be elucidated. Therefore, SS-cream may be effective for future treatment of mild erectile dysfunction, in addition to its role for premature ejaculation.
Animal ; Ejaculation/drug effects ; In Vitro ; Male ; Muscle Contraction/drug effects ; Muscle, Smooth/drug effects ; Penile Erection/drug effects ; Penis/*drug effects/physiology ; Plant Extracts/*pharmacology ; Rabbits

OBJECTIVETo observe and compare the effects of 17beta-estradiol (EST) on the phasic and tonic contractile activities of the uterine smooth muscles of SD rats in vitro.

METHODSDifferent concentrations of 17beta-estradiol were added into the perfusion muscular sockets containing uterine smooth muscles of SD rats, and the activities of muscle contraction were recorded at the same time.

RESULTS17beta-estradiol had obvious depression effects on spontaneous rhythmic contraction of the uterine smooth muscles in a concentration-dependent manner, it could considerably decrease muscular tension, the mean amplitudes and frequencies of contractile waves (P < 0.01); it could also suppress the uterine contraction stimulated by KCl, CaCl2 or prostaglandin F2alpha (PGF2alpha). Based on the contraction of uterine smooth muscle stimulated by KCl, IC50 was 7.278 micromol/L and pD2 was -0.862 when calculated by linear regression method. 17beta-estradiol could also inhibit the maximal CaC12 contraction of uterine smooth muscle in the Ca2+ free Krebs solution, which the ECQ was 1.422 x 10(-3) mol/L, pD2 was 2.847 (control), but the E50 was 3.028 x 10(-3) mol/L, p2 was 2.519 (added with EST) when calculated by linear regression method.

CONCLUSIONThe depression effects of 17beta-estradiol on the spontaneous rhythmic contraction and activated contraction of the uterine smooth muscles of SD rats could be mediated through the blockage of C2+ influx through potential-dependent Ca2+ channels of plasma membrane.

Animals ; Estradiol ; pharmacology ; Female ; Muscle, Smooth ; drug effects ; Myometrium ; drug effects ; Rats ; Rats, Sprague-Dawley ; Uterine Contraction ; drug effects

OBJECTIVETo investigate the effect of morphine chloride on small intestinal muscle in vitro or in vivo and its mechanisms.

METHODSContractile amplitude, tension and frequency of the isolated small intestine of rabbits were measured before and after treatment of morphine chloride. The propulsive distance of magenta in intestinal tract was measured when different concentration of morphine chloride was given orally in mice.

RESULTAfter treatment of different concentration of morphine chloride (5 mg/L, 10 mg/L, 30 mg/L), the contractile activities of isolated small intestines of rabbits decreased significantly. The inhibitory effect of morphine chloride was blocked by naloxone, atropine, but potentiated by regitine. The propulsive distance of magenta in intestinal tract of intact mouse decreased after treatment with morphine chloride of various concentration (75, 150, 300 mg/L).

CONCLUSIONMorphine chloride has an inhibitory effect on the contractility of rabbit small intestine in vitro or in vivo. Opioid receptor, choline and adrenal receptor might be involved in this effect.

Animals ; Female ; Gastrointestinal Transit ; drug effects ; In Vitro Techniques ; Intestine, Small ; drug effects ; Male ; Mice ; Morphine ; pharmacology ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; Rabbits

The effects of the alcohol extract of Panax ginseng on the myocardial contractility particularly with respect to Bowditch and Woodworth phenomena and the norepinephrine induced contraction of the vascular smooth muscle were studied in vitro. 1) In the isolated muscle preparation of guinea pig left auricle, the administration of ginseng-alcohol extract at concentrations of 10~50mg% resulted in a significant reduction of both Bowditch and Woodworth effects. 2) In the isolated Ca++ depleted heart of rabbit ginseng-alcohol extract inhibited the Ca++ uptake and the restoration of contractile force during perfusion with a Ca++ containing solution. 3) In the isolated muscle strip of the rabbit aorta noradrenaline (5 X 10-8 g/ml) induced contraction was inhibited by the ginseng-alcohol extract at concentrations of 10~50mg%. From these results it is speculated that the hypotensive effect of ginseng is accounted for by 1) the direct inhibition of myocardial contractility which is resulted from the reduction of Ca++ influx into cardiac cell, and 2) the inhibition of the catecholamine induced contractility of vascular smooth muscles.
Animal ; Aorta/drug effects ; Cardiovascular System/drug effects* ; Ethanol/pharmacology ; Female ; Guinea Pigs ; In Vitro ; Male ; Muscle Contraction/drug effects ; Muscle, Smooth/drug effects ; Myocardial Contraction/drug effects* ; Panax* ; Plant Extracts/pharmacology* ; Plants, Medicinal* ; Rabbits

To investigate the role of ligustrazine on relaxation of the isolated rabbit corpus cavernosum tissue in vitro, the effects of ligustrazine on the corpus cavernosum were observed by using experimental method of smooth muscle strips. Concentration-responses to phenylephine (PE) and KCl were recorded. The results showed that ligustrazine concentration-dependently depressed the contraction response of smooth muscle strips induced by PE. The maximum percentage relaxation of cavernosal strips by ligustrazine was 74.1% +/- 6.2% (compared with control: 21.9% +/- 5.6%, P < 0.01). Ligustrazine concentration-dependently reduced the amplitude of the contraction induced by cumulative doses of PE or KCl, shifted the cumulative concentration response curves of PE and KCI to the right and depressed their maximal responses. It was concluded that ligustrazine could significantly relax the cavernosal muscle contraction induced by PE in vitro. The results suggested that ligustrazine inhibited calcium ion influx.
Calcium Channels/drug effects ; Muscle Contraction/*drug effects ; Muscle Relaxation/*drug effects ; Muscle, Smooth/*drug effects ; Muscle, Smooth/physiology ; Penis/*drug effects ; Penis/physiology ; Phenylephrine/pharmacology ; Potassium Chloride/pharmacology ; Pyrazines/*pharmacology

OBJECTIVETo investigate the effect of ascorbic acid (VC) on relaxation of ex vivo Bufo gastrocnemius during sustained isometric contraction.

METHODSDynamic tension of the muscle was recorded under constant voltage stimulation within 7.0 min at 2 s intervals. The rest tension and relaxation rate of the muscle was obtained by weighted fitting to the relaxation process of tension <90% of its peak with a mono-exponential model to characterize the muscular relaxation.

RESULTSVC at 2.0 mmol/L alone or in combination with the inhibitors of the antixoidation enzymes (surperoxide dismutase, glutathione peroxidase and catalase) resulted in negligible alterations in the muscular relaxation kinetics. VC combined with the inhibitor of surperoxide dismutase resulted in significantly lowered relaxation rate while increased rest tension, but VC with the inhibitor of either catalase or glutathione peroxidase showed negligible action. VC combined with the inhibitors of all the 3 enzymes also caused significant effect on the muscular relaxation kinetics, which was similar the effect of VC with superoxide dismutase inhibitor.

CONCLUSIONVC at high concentration may result in oxidative toxicity to the biological system rich in transitional metal ion complexes but with low antioxidation capacity by causing superoxide-mediated oxidative damages.

Animals ; Ascorbic Acid ; pharmacology ; Bufonidae ; Electric Stimulation ; In Vitro Techniques ; Isometric Contraction ; drug effects ; Muscle Relaxation ; drug effects ; Muscle, Skeletal ; drug effects ; physiology

Animals ; Cholagogues and Choleretics ; pharmacology ; Drugs, Chinese Herbal ; pharmacology ; Gardenia ; chemistry ; In Vitro Techniques ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; physiology ; Rabbits ; Stomach ; drug effects

The aim of this study was to investigate the inhibitory effect and the underlying mechanism of ethacrynic acid (EA) on the contraction in mice. BL-420S force measuring system was used to measure the tension of mouse tracheal rings. The whole cell patch clamp technique was utilized to record the channel currents of airway smooth muscle (ASM) cells. The calcium imaging system was used to determine the intracellular Ca concentration ([Ca]) in ASM cells. The results showed that EA significantly inhibited the high K (80 mmol/L) and acetylcholine (ACh, 100 µmol/L)-induced contraction of mouse tracheal rings in a dose-dependent manner. The maximal relaxation percentages were (97.02 ± 1.56)% and (85.21 ± 0.03)%, and the median effective concentrations were (40.28 ± 2.20) μmol/L and (56.22 ± 7.62) μmol/L, respectively. EA decreased the K and ACh-induced elevation of [Ca] from 0.40 ± 0.04 to 0.16 ± 0.01 and from 0.50 ± 0.01 to 0.39 ± 0.01, respectively. In addition, EA inhibited L-type voltage-dependent calcium channel (LVDCC) and store-operated calcium channel (SOCC) currents in ASM cells, and Ca influx. Moreover, EA decreased the resistance of the respiratory system (Rrs) in vivo in mice. These results indicated that EA inhibits LVDCC and SOCC, which results in termination of Ca influx and decreases of [Ca], leading to relaxation of ASM. Taken together, EA might be a potential bronchodilator.
Animals ; Calcium ; metabolism ; Calcium Channels, L-Type ; Enzyme Inhibitors ; pharmacology ; Ethacrynic Acid ; pharmacology ; Mice ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; Respiratory System ; cytology ; drug effects