• The Korean Journal of Physiology and Pharmacology
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• 제13권5호
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• pp.393-400
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• 2009

NO released by myenteric neurons controls the off contraction induced by electrical field stimulation (EFS) in distal esophageal smooth muscle, but in the presence of nitric oxide synthase (NOS) inhibitor, L-NAME, contraction by EFS occurs at the same time. The authors investigated the intracellular signaling pathways related with G protein and ionic channel EFS-induced contraction using cat esophageal muscles. EFS-induced contractions were significantly suppressed by tetrodotoxin ($1\;{\mu}M$) and atropine ($1\;{\mu}M$). Furthermore, nimodipine inhibited both on and off contractions by EFS in a concentration dependent meaner. The characteristics of 'on' and 'off contraction and the effects of G-proteins, phospholipase, and $K^+$ channel on EFS-induced contraction in smooth muscle were also investigated. Pertussis toxin (PTX, a $G_i$ inactivator) attenuated both EFS-induced contractions. Cholera toxin (CTX, $G_s$ inactivator) also decreased the amplitudes of EFS-induced off and on contractions. However, phospholipase inhibitors did not affect these contractions. Pinacidil (a $K^+$ channel opener) decreased these contractions, and tetraethylammonium (TEA, ${K^+}_{Ca}$ channel blocker) increased them. These results suggest that EFS-induced on and off contractions can be mediated by the activations Gi or Gs proteins, and that L-type $Ca^{2+}$ channel may be activated by G-protein ${\alpha}$ subunits. Furthermore, ${K^+}_{Ca^-}$ channel involve in the depolarization of esophageal smooth muscle. Further studies are required to characterize the physiological regulation of $Ca^{2+}$ channel and to investigate the effects of other $K^+$ channels on EFS-induced on and off contractions.

• 대한수학회논문집
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• 제27권1호
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• pp.117-128
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• 2012

Using the concept of a g-monotone mapping we prove some common fixed point theorems for g-non-decreasing mappings which satisfy some generalized nonlinear contractions in partially ordered complete quasi b-metric spaces. The new theorems are generalizations of very recent fixed point theorems due to L. Ciric, N. Cakic, M. Rojovic, and J. S. Ume, [Monotone generalized nonlinear contractions in partailly ordered metric spaces, Fixed Point Theory Appl. (2008), article, ID-131294] and R. P. Agarwal, M. A. El-Gebeily, and D. O'Regan [Generalized contractions in partially ordered metric spaces, Appl. Anal. 87 (2008), 1-8].

• The Korean Journal of Physiology
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• 제19권1호
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• pp.1-13
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• 1985

The influences of $Ca^{2+}-antagonists$, verapamil and $Mn^{2+}$, upon the spontaneous electrical activity and contractions were studied in guinea-pig taenia coli. Spontaneous contractions were recorded with force transducer, and spike action potentials were measured extracellularly by use of suction electrode. All experiments were performed in tris-buffered Tyrode solution Which was aerated With 100% $O_2$ and kept at $35^{\circ}C$. The results obtained were as follows : 1) Verapamil suppressed the frequency and amplitude of spontaneous contractions dose dependently, and blocked completely mechanical responses at the concentration of 1 mg/1. 2) The frequency of bursts of spike discharge(bursts frequency) and the number of spikes in a burst(spikes frequency) were reduced in a dose·dependent manner within the concentration range of $10^{-5}$ to $10^{-3}g/l$, and bursts frequency was affected more readily at a low concentration of $10^{-5}g/l$ verapamil. 3) The verapamil_induced suppression of spontaneous contractions in the Tyrode solution containing 1 mM $Ca^{2+}$ was completely antagonized by the addition of extra $Ca^{2+}$ to the Tyrode solution $(2\;m\;MCa^{2+})$. 4) $Mn^{2+}$ suppressed the amplitude of spontaneous contractions, whereas $Mn^{2+}$ accelerated the frequency dose-dependently within the range of low concentrations$(10^{-7}\;to\;10^{-4}\;M\;Mn^{2+})$. 5) The bursts frequency determining frequency of spontaneous contractions was increased in a dose-dependent manner, whereas the spikes frequency known to determine the contractions amplitude was reduced within the range of low concentrations. At a high concentration of 1 mM $Mn^{2+}$, however, all spontaneous contractile responses were blocked simultaneously with the disapperance of electrical activity. 6) The frequency and amplitude of spontaneous contractions altered by $Mn^{2+}$ in 1mM $Ca^{2+}$ Tyrode were increased by extra $Ca^{2+}(2mM)$.

• The Korean Journal of Physiology and Pharmacology
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• 제27권4호
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• pp.325-331
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• 2023

α₁-adrenoceptors link via the G-protein Gq/G₁₁ to both Ca²⁺ entry and release from stores, but may also activate Rho kinase, which causes calcium sensitization. This study aimed to identify the subtype(s) of α₁-adrenoceptor involved in Rho kinase-mediated responses in both rat aorta and mouse spleen, tissues in which contractions involve multiple subtypes of α₁-adrenoceptor. Tissues were contracted with cumulative concentrations of noradrenaline (NA) in 0.5 log unit increments, before and in the presence of an antagonist or vehicle. Contractions produced by NA in rat aorta are entirely α₁-adrenoceptor mediated as they are competitively blocked by prazosin. The α_1A-adrenoceptor antagonist RS100329 had low potency in rat aorta. The α_1D-adrenoceptor antagonist BMY7378 antagonized contractions in rat aorta in a biphasic manner: low concentrations blocking α_1D-adrenoceptors and high concentrations blocking α_1B-adrenoceptors. The Rho kinase inhibitor fasudil (10 µM) significantly reduced aortic contractions in terms of maximum response, suggesting inhibition of α_1B-adrenoceptor mediated responses. In the mouse spleen, a tissue in which all 3 subtypes of α₁-adrenoceptor are involved in contractions to NA, fasudil (3 µM) significantly reduced both early and late components to the NA contraction, the early component involving α_1B- and α_1D-adrenoceptors, and the late component involving α_1B- and α_1A-adrenoceptors. This suggests that fasudil inhibits α_1B-adrenoceptor mediated responses. It is concluded that α_1D- and α_1B-adrenoceptors interact in rat aorta and α_1D-, α_1A- and α_1B-adrenoceptors interact in the mouse spleen to produce contractions and these interactions suggest that one of the receptors preferentially activates Rho kinase, most likely the α_1B-adrenoceptor.

• Journal of applied mathematics & informatics
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• 제38권5_6호
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• pp.507-518
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• 2020

In this article, we establish some fixed point results in G-metric spaces using the modified JS-G-contractions and we provide some suitable examples to support the results. Also, we give an application to solve an integral equation.

• Journal of Ginseng Research
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• 제17권2호
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• pp.109-113
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• 1993

The effects of ginseng total saponins (GTS) on the action of U-50,488H, a $textsc{k}$-opioid receptor agonist, on the electrically induced twitch responses of mouse vats deferens were studied. U-50,488H ($10^9$~$10^{-5}$M) inhibited the twitch contractions in a dose-dependent manner, which were caused by adenosine 5'-triphosphate (ATP) released from the stimulated sympathetic nerve, and this effect was antagonized by naloxone ($10^6$ M). GTS, which itself induced the inhibition of the twitch contractions, acted additively to U-50,488H, GTS and U-50,488H had no effect on the tension of the unstimulated organs. The contractions elicited by ATP were not affected by U-50,488H, but inhibited by GTS. These results suggest that U-50,488H suppressed the twitch contractions by the inhibition of neurotransmitter release from presynaptic nerve terminals via action on opioid receptor, but G75, by inhibiting the action of the neurotransmitter on the smooth muscle.

• The Korean Journal of Physiology and Pharmacology
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• 제13권3호
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• pp.241-249
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• 2009

Although extracellular $Ca^{2+}$ entry through the voltage-dependent $Ca^{2+}$ channels plays an important role in the spontaneous phasic contractions of the pregnant rat myometrium, the role of the T-type $Ca^{2+}$ channels has yet to be fully identified. The aim of this study was to investigate the role of the T-type $Ca^{2+}$ channel in the spontaneous phasic contractions of the rat myometrium. Spontaneous phasic contractions and $[Ca^{2+}]_i$ were measured simultaneously in the longitudinal strips of female Sprague-Dawley rats late in their pregnancy (on day 18 ${\sim}$ 20 of gestation: term=22 days). The expression of T-type $Ca^{2+}$ channel mRNAs or protein levels was measured. Cumulative addition of low concentrations (< 1 ${\mu}M$) of nifedipine, a L-type $Ca^{2+}$ channel blocker, produced a decrease in the amplitude of the spontaneous $Ca^{2+}$ transients and contractions with no significant change in frequency. The mRNAs and proteins encoding two subunits (${\alpha}$ 1G, ${\alpha}$ 1H) of the T-type $Ca^{2+}$ channels were expressed in longitudinal muscle layer of rat myometrium. Cumulative addition of mibefradil, NNC 55-0396 or nickel induced a concentration-dependent inhibition of the amplitude and frequency of the spontaneous $Ca^{2+}$ transients and contractions. Mibefradil, NNC 55-0396 or nickel also attenuated the slope of rising phase of spontaneous $Ca^{2+}$ transients consistent with the reduction of the frequency. It is concluded that T-type $Ca^{2+}$ channels are expressed in the pregnant rat myometrium and may play a key role for the regulation of the frequency of spontaneous phasic contractions.

• Biomolecules & Therapeutics
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• 제2권2호
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• pp.173-184
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• 1994

The general and some pharmacological actions of DWP 305 were investigated in animals and the following results were obtained. In central nervous system, DWP 305 had no effects on the pentobarbital induced anaesthesia, locomotor activity, rotarod test, traction test, analgesic action in mice and body temperature in rat. DWP 305 showed no depressive action on convulsion induced by strychnine, electronic shock and pentylenetetrazole. From these results, DWP 305 was considered to have no pharmacological effect on the central nervous system. Furthermore, DWP 305 had no influences on the normal blood pressure and heart rate. In the isolated ileum of guinea pig, DWP 305 inhibited contractive effects against the acetylcholine (10$^{-6}$ g/mι), histamine (10$^{-6}$ g/mι), 5-hydroxytryptamine (10$^{-6}$ g/mι) and BaCl$_2$(10$^{-4}$ g/mι) at a concentration of 2.15$\times$10$^{-4}$ g/ml in bath. In the isolated trachea and vats deference, DWP 305 showed no effect on the contractions produced by histamine and norepinephrine, respectively. DWP 305 showed inhibitory effect on the contractions produced by acetylcholine and oxytocin at a concentration of 2.15$\times$10$^{-4}$ g/ml on the isolated nonpregnant rat uterus. DWP 305 had no effect on the isolated right atrium of guinea pig, bile excretion, urine volume, pH, gastrointestinal motility, gastric secretion and blood aggregation.

• Nonlinear Functional Analysis and Applications
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• 제26권1호
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• pp.13-33
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• 2021

The aim of this paper is to establish common fixed point theorems under generalized (ψ - ϕ)-weak contractions in the setting of complete S-metric spaces and we support our result by some examples. Also an application of our results, we obtain some fixed point theorems of integral type. Our results extend Theorem 2.1 and 2.2 of Doric [5], Theorem 2.1 of Dutta and Choudhury [6], and many other several results from the existing literature.

• Journal of applied mathematics & informatics
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• 제39권3_4호
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• pp.529-539
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• 2021

The purpose of this paper is to prove some fixed point theorems using (𝜓, 𝜑)-contractions via the concept of C-class functions in G_b-metric spaces. Moreover, an example is presented to illustrate the validity of our results.