• Journal of Chest Surgery
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• v.16 no.2
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• pp.199-212
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• 1983

The inhibition/influences of adenine compounds on the heart have been described repeatedly by many investigators, since the first report by Druny and Szent-Gyorgyi [1929]. These studies have shown that adenosine and adenine nucleotides have an over-all effect similar to that of acetylcholine [ACh] by slowing and weakening the heartbeat. The basic cellular and membrane events underlying the inhibitory action of adenosine on sinus rate, however, are not well understood. Furthermore, the physiological role of adenosine in regulation of the heartbeat remains still to be elucidated. Therefore, this study was undertaken in order to examine the response of rabbit SA node to adenosine and to compare the response to that of ACh. Isolated SA node preparation, whole atrial pair, or left atrlal strip was used in each experiment. Action potentials of SA node were recorded through the intracellular glass microelectrodes, which were filled with 3M KCI and had resistance of 30-50 M. All experiments were performed in a bicarbonate-buffered Tyrode solution which was aerated with 3% $CO_2-97%$ $O_2$ gas mixture and kept at $35^{\circ}C$. Spontaneous firing rate of SA node at 35C [Mean + SEM, n=16] was 154 + 3.3 beats/min. The parameters of action potentials were: maximum astolic potential [MDP], -731.7mV: overshoot [OS], 9 + 1.4mV; slope of pacemaker potential [SPP], 94 3.0mV/sec.Adenosine suppressed the firing rate of SA node in a dose dependent manner. This inhibitory effect appeared at the concentration of $10^{-6}M$ and was potentiated in parallel with the increase in adenosine concentration. Changes in action potential by adenosine were dose-dependent increase of MDP and decrease of SPP until $10^{-4}$. Above this concentration, however, the amplitude of action potential decreased markedly due to the simultaneous decrease of both MDP and OS. All these effects of adenosine were not affected by pretreatment of atropine [2mg/l] and propranolol [$5{\times}10^{-6}M$]. ACh [$10^{-6}M$] responses on action potential were similar to those of adenosine by increasing MDP and decreasing SPP. These effects of ACh disappeared by pretreatment of atropine [2mg/1]. Inhibition/effects of adenosine and ACh on sinus rate were enhanced synergistically with the simultaneous administration of adenosine and ACh. Marked decrease of overshoot potential was the most prominent feature on action potential. Dipyridamole [DPM], which is known to block the adenosine transport across cell membrane, definitely potentiated the action of adenosine . Adenosine suppressed the sinus rate and atrial contractility in the same dosage range, even in the reserpinized preparation. Above` results suggest that adenosine suppresses pacemaker activity, like ACh, by acting directly on the membrane of SA node, increasing MDP and decreasing SPP.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.4
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• pp.603-607
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• 2011

The purpose of this study is to investigate the effects of Carthami Flos on interstitial cells of Cajal in the gastrointestinal tract. Many regions of the tunica muscularis of the gastrointestinal (GI) tract display spontaneous contraction. These spontaneous contractions are mediated by periodic generation of electrical slow waves. Recent studies have shown that the interstitial cells of Cajal (ICCs) act as pacemakers and conductors of electrical slow waves in gastrointestinal smooth muscles. We investigated the cytotoxicity activity, antioxidant activity, and pacemaking activity. The cytotoxicity activity was measured by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Antioxidant activities were determined by DPPH (1.1-diphenyl-2-picrylhydrazyl) radical scavenging capacity assay and DCFH-DA (2,7-dichlorofluorescein diacetate) method. The effects of Carthami Flos on the pacemaker potentials in cultured ICCs from murine small intestine were investigated by using whole-cell patch-clamp techniques at $30^{\circ}C$. The addition of Carthami Flos (5, 10, $30{\mu}g$/ml) depolarized the resting membrane potentials in a concentration dependent manner. These results suggest that the GI tract can be targets for Carthami Flos, and their interaction can affect intestinal motility.

• Journal of Korean Neurosurgical Society
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• v.42 no.3
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• pp.205-210
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• 2007

Objective : Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels mediate the hyperpolarization-activated currents (Ih) that participate in regulating neuronal membrane potential and contribute critically to pacemaker activity, promoting synchronization of neuronal networks. However, distinct regional and cellular localization of HCN channels in the brain have not been precisely defined. Aim of this study was to verify the precise cellular location of HCN1 channels in rat cerebellum to better understand the physiological role these channels play in synaptic transmission between CNS neurons. Methods : HCN1 expression in rat brain was analyzed using immunohistochemistry and electron-microscopic observations. Postsynaptic density-95 (PSD-95), otherwise known as locating and clustering protein, was also examined to clarify its role in the subcellular location of HCN1 channels. In addition, to presume the binding of HCN1 channels with PSD-95, putative binding motifs in these channels were investigated using software-searching method. Results : HCN1 channels were locally distributed at the presynaptic terminal of basket cell and exactly corresponded with the location of PSD-95. Moreover, nine putative SH3 domain of PSD-95 binding motifs were discovered in HCN1 channels from motif analysis. Conclusion : Distinct localization of HCN1 channels in rat cerebellum is possible, especially when analyzed in conjunction with the SH3 domain of PSD-95. Considering that HCN1 channels contribute to spontaneous rhythmic action potentials, it is suggested that HCN1 channels located at the presynaptic terminal of neurons may play an important role in synaptic plasticity.

• The Korean Journal of Physiology
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• v.19 no.2
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• pp.127-137
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• 1985

The present study was undertaken in order to investigate effect of ethanol extract of Rehmanniae radix(RREE) on electrophysiology of sinus node and papillary muscle. Rehmanniae radix is a herbal medicine which has been known to have diuretic, antipyretic, hemopoietic and cardiotonic effects. Action potentials were recorded by means of glass capillary microelectrode(technique) in rabbit sinoatrial nodal cells and papillary muscle cells which were superperfused with either tyrode solution or tyrode solutions containing different amount of RREE. The results obtained were as follows ; 1) In both central and peripheral nodal cells maximum diastolic potential (MDP) and amplitude of action potential (APA) were not affected by RREE. 2) Action potential duration as expressed $APD_{60}$(time to 60% repolarization) of central and peripheral pacemaker cells were significantly prolonged following perfusion with tyrode solution containing 0.1% RREE. 3) The rates of spontaneous firing from central pecemaker cell were decreased by RREE at concentration of 0.05% and 0. 1% while spontaneous rhythm of perinodal cell was decreased by 0.1% RREE. 4) The action potential duration of papillary muscle as expressed $APD_{60}$ were prolonged by 0.1% RREE.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.4
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• pp.193-198
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• 2006

Many gastrointestinal muscles show electrical oscillation, so-called 'slow wave', originated from interstitial cells of Cajal (ICCs). Thus, a technique to freshly isolate the cells is indispensable to explore the electrophysiological properties of the ICCs. To apply an enzyme solution on the serosal surface for cell isolation, the intestine was inverted and 0.02% trypsin solution and 0.04% collagenase solution were applied to serosal cavity. After the enzyme treatment, mucosal layer was removed and longitudinal muscle layer was gently separated from the rest of tissue. The thin layer was stretched in the recording chamber and mounted on an inverted microscope. Using ${\beta}-escine$, perforated whole cell patch clamp technique was used. Under a microscope, the tissue showed smooth muscle cells and interstitial cells around the myenteric plexus. Under voltage clamp condition, three types of membrane potential were recorded. One group of interstitial cells, which were positive to methylene blue and CD34, showed spontaneous outward current. These cells had bipolar shape and were considered as fibroblast-like cells because of their peculiar shape and arrangement. Another group, positive to c-kit and methylene blue, showed spontaneous inward current. These cells had more rounded shape and processes and were considered as ICCs. The third, positive to c-kit and had granules containing methylene blue, showed quiet membrane potentials under the voltage-clamp mode. These cells appeared to be resident macrophages. Therefore, in the freshly isolated thin tissue preparation, methylene blue could easily identify three types of cells rather than morphological properties. Using this method, we were able to study electrical properties of fibroblast and residential macrophage as well as myenteric ICCs.