• YAKHAK HOEJI
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• v.32 no.2
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• pp.129-136
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• 1988

Effects of the selective alpha-adrenoceptor agonists, clonidine, oxymetazoline and phenylephrine, on heart rate and contractile force were investigated in the isolated frog atria and it was attempted to examine the influence of adrenoceptor antagonist upon those. Clonidine produced dose-dependent negative chronotropic and positive inotropic effects. The negative chronotropic effect was significantly attenuated in the presence of prazosin and yohimbine but not propranolol. The positive inotropic effect was significantly attenuated by prazosin, yohimbine and propranolol. Oxymetazoline produced dose-dependent negative chronotropic and inotropic effects. The negative chronotropic effect was significantly attenuated in the presence of prazosin, which was partially augmented by yohimbine but was not affected by propranolol. The negative inotropic effect was not affected by propranolol but it was partially augmented by yohimbine and was partially attenuated by prazosin. Phenylephrine produced dose-dependent positive chronotropic and inotropic effects. The positive chronotropic and inotropic effect were significantly attenuated in the presence of propranolol but were not affected by prazosin and yohimbine. These results suggest that the negative chronotropic effect by clonidine and oxymetazoline is mediated by alpha-adrenoceptors, the positive chronotropic and inotropic effects by phenylephrine are mediated by beta-adrenoceptors, and alpha-adrenoceptors mediated the inhibitory chronotropic responses exists in the isolated frog atria.

• Archives of Pharmacal Research
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• v.11 no.1
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• pp.65-73
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• 1988

The effects of clonidine on the negative chronotropic response induced by stimulation of vagus nerve were studied in the presence of propranolol in reserpinized and anesthetized rats. When the heart rate was decreased by stimulation of the vagus nerve, clonidine significantly inhibited vagally induced heart rate decrease (negative chronotropic response) in dose dependent manner. This inhibitory effect of clonidine was virtually abolished by phentolamine, ${\alpha}_1-\;and\;{\alpha}_2-adrenoceptor$ antagonist, and partially antagonized by prazosin, ${\alpha}_1-adrenoceptor$ antagonist. On the other hand, when the heart rate was decreased by the infusion of bethanechol, a muscarinic parasympathetic stimulant, clonidine had no effect on the bethanechol-induced heart rate decrease. These results suggest that clonidine inhibits vagally induced negative chronotropic response by activation of presynaptic ${\alpha}-adrenoceptors$ located on the parasympathetic cholinergic nerve terminal in the heart and this effect of clonidine is more related to ${\alpha}_2-adrenoceptors$ than ${\alpha}_1-adrenoceptors$.

• The Korean Journal of Physiology
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• v.21 no.1
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• pp.1-12
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• 1987

There is evidence that the effect of extracellular $Ca^{2+}$ on heart rate is temperature-dependent: at $38^{\circ}C$ excess $Ca^{2+}$ induces positive chronotropic response, whereas at $30^{\circ}C$ there is no significant chronotropic effect of $Ca^{2+}$. The cause of this temperature-dependency, however, remains still unclear. Therefore, this study was undertaken to investigate the chronotropic effect of external $Ca^{2+}$ at different temperature in the isolated rabbit atria and in the small strips of SA node cut perpendicularly to crista terminalis. In the isolated atria, the $Ca^{2+}$ effect was temperature-dependent: at $35^{\circ}C$ excess $Ca^{2+}$ evoked positive chronotropic response, while at $30^{\circ}C$ there was no significant changes in sinus rate. On the contrary, in the small SA strips external $Ca^{2+}$ induced negative chronotropic effect. At $35^{\circ}C$ changes in $Ca^{2+}$ concentration from 2 to 4, 6, and 10 mM decreased the sinus rate by $2.7{\pm}1.6%$, $11.2{\pm}3.7%$ and $23.2{\pm}8.1%$ respectively. Lowering the temperature to $30^{\circ}C$, the negative chronotropic effect of $Ca^{2+}$ became greater. With intracellular microelectrodes transmembrane potential was recorded in the small SA strips at $30^{\circ}C$, $35^{\circ}C$ and $38^{\circ}C$. As temperature increased from 30 to $38^{\circ}C$, sinus rate was accelerated by $13/min/^{\circ}C$, $APD_{50}$(action ptential duration from peak to 50% repolarization) decreased by $5\;msec/^{\circ}C$, and amplitude of action potential was slightly decreased. With an increase in $Ca^{2+}$ concentrations from 0.5 to 6 mM, overshoot increased and MDP decreased. These $Ca^{2+}$ effects on the overshoot and MDP of action potentials were not altered by temperature. But the $Ca^{2+}$ effects on the rates of diastolic depolarization, systolic depolarization and repolarization were modified by temperature. Discrpancy of the chronotropic effects of $Ca^{2+}$ between isolated atria and small SA strips was discussed.

• Archives of Pharmacal Research
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• v.7 no.1
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• pp.61-62
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• 1984

The toxicity of water extracts from intestine parts (digestive tract respiratory tree) of Korean Stichopus japonicus was determined using mouse units and more purified substance decreases the amplitude of contraction of guinia pig atria in vitro; showes negative chronotropic and ionotropic effects in the spontaneously beating guinea pig atria.

• The Korean Journal of Pharmacology
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• v.13 no.1 s.21
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• pp.7-12
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• 1977

Recently several reports have claimed that the bath temperature changes, such as lower bath temperature, produce supersensitivity on the positive chronotropic effect of catecholamine in cat, mouse and guinea pig atria. However, others showed controversial results against temperature-dependent supersensitivity. Similarly, the inotropic effect of ouabain is diminished in febrile state, however some investigators indicated that cardiac glycoside showed less toxicities and less effects in hypothermic condition. In this study, the effects of norepinephrine and epinephrine on inotropy and chronotropy in isolated rat atria was investigated by changing the temperature of bath ($30^{\circ}C$, $^35{\circ}C$ and $38^{\circ}C$). In addition, the effects of ouabain on atria in hypothermic bath was also studied. The followings are the results. 1. At the lower bath temperature isolated rat atrial rate was decreased and contractility was increased. 2. The chronotropic responses to norepinephrine and epinephrine in $38^{\circ}C$ were decreased when the bath temperature lowered to $35^{\circ}C$ or $30^{\circ}C$, while the inotropic responses were not affected. 3. Hypothermic supersensitivity to norepinephrine or epinephrine was not observed in rat atrium. 4. The inotropic response to ouabain was potentiated but chronotropic response was diminished by a lowering in the bath temperature. In conclusion, the chronotropic response of rat atrium to catecholamine was decreased, however, hypothermic supersensitivity was no longer present in rat atrium and the inotropic response of ouabain was increased at lower bath temperature.

• The Korean Journal of Physiology
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• v.9 no.2
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• pp.23-31
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• 1975

The effects of ethanol intravenously administered on the mean arterial blood pressure and heart rate responses to electrical stimulation of vagus nerve and the hypothalamus were studied in the cats. Also investigated were the effects of ethanol on the cardiovascular responses to bilateral carotid occlusion and to intravenously injected epinephrine and acetylcholine separately. The results obtained from the present study were as follows; 1. In 1.0 ml/kg and 2.0 ml/kg of ethanol infused groups the mean arterial blood pressure increased gradually and reached plateaus in 10 minutes after ethanol infusion while no marked changes in blood pressure were observed in 0.5 ml/kg of ethanol infused group. 2. The pressor responses elicited by the electrical stimulation of the hypothalamus were depressed directly proportionally to amount of ethanol infused. In 0.5 ml/kg of ethanol infused group the pressor response was reduced to 84.5% of control value and it declined to 17.0% of control in 2.0 ml/kg of ethanol infused group. 3. After ethanol administration the heart rate decreased slightly and also was decreased positive chronotropic effect elicited by hypothalamic stimulation. In several cases even negative chronotropic responses were observed during electrical stimulation in the hypothalamus. 4. Since the pressor responses to bilateral carotid occlusion was reduced by ethanol administration it is suggested that activity of baroreceptor is inhibited by ethanol. 5. No changes were observed in the negative chronotropic effect Produced by electrical stimulation of the vegus nerve of ethanol infused animal. And cardiovascular responses to intravenously injected epinephrine and acetylcholine were not influenced by ethanol either.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.290-300
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• 2000

One of the most important topics in attentional and emotional modulation of cardiac responses is time course of cardiac chronotropic response. The reason lies in dual innervation of heart, which leads to occurrence of several phases of cardiac response during exposure to affective stimuli, determined by the balance of sympathetic and parasympathetic influences. Cardiac chronotropic reactivity thus represents quite effective measure capable to trace the moment when attending and orienting processes (i.e., sensory intake of stimulus) prime relevant behavioral response (ile., emotion with approach or avoidance tendencies). The aim of this study was to find the time course of heart rate (HR) responses typical for negative (disgust, surprise, fear, anger) and positive (happiness, pleasant erotic) affective pictures and to identify cardiac response dissociation for emotions with different action tendencies such as "approach" (surprise, anger, happiness) and "avoidance" (fear, sadness, disgust). Forty college students participated in this study where cardiac responses to slides from IAPS intended to evoke basic emotions (surprise, fear, anger, sadness, disgust, happiness, pleasant-erotic). Inter-beat intervals of HR were analyzed on every 10 sec basis during 60 sec long exposure to affective visual stimuli. Obtained results demonstrated that differentiation was observed at the very first 10s of exposure (anger-fear, surprise-sad, surprise-erotic, surprise-happiness paris), reaching the peak of dissociation at 30s (same pairs plus surprise-disgust and surprise-fear) and was still effective for some pairs (surprise-erotic, surprise-sad) even at 50s and 60s. discussed are potential cardiac autonomic mechanisms underlying attention and emotion processes evoked by affective stimulation and theoretical considerations implicated to understand the role of differential cardiac reactivity in the behavioral context (e.g., approach-avoidance tendencies, orienting-defense responses).

• Natural Product Sciences
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• v.5 no.1
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• pp.25-32
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• 1999

The pharmacological actions of ambrein were investigated alone or in combination as a pretreatment with agonists (adrenaline, noradrenaline, acetylcholine, histamine, nicotine), antagonists (atropine, atenolol) and calcium channel blocker (verapamil) in vivo in anaesthetized SWR rats using blood pressure, heart rate and myocardial contractility as parameters. Ambrein in the dose range of 50-200 mg/kg to the normotensive anaesthetized rats demonstrated negative chronotropic effect and increased the myocardial contractility significantly. At the mid dose (100 mg/kg) this increase in contractile force was 36% and 44% above the normal at 30 min and 60 min intervals post-treatment, respectively. Both of the lower and high doses (50 mg/kg and 200 mg/kg) had similar effects. Furthermore, this contractile response was dose related. Also, this compound produced a considerable increase in myocardial contractility when used as a pretreatment with some agonists and antagonists. The results on blood pressure did not show a considerable change when ambrein was used alone. However, ambrein pretreatment at the dose of 100 mg/kg did not block the effects of adrenaline, noradrenaline, isoprenaline and acetylcholine on heart rate and blood pressure. On the other hand, this pretreatment attenuated the sympathoadrenal effects of nicotine significantly. Chronotropic and blood pressure changes produced by histamine were also inhibited by ambrein pretreatment. This pretreatment significantly reversed the effects of atenolol but failed to demonstrate any change in the negative chronotropic, inotropic and hypotensive responses induced by verapamil. It is concluded that ambrein induced nonselective dose dependent antagonism of the effects of some agonists and antagonists require contribution of some neuromediators. However, the positive isotropic effects of ambrein possibly involve the enhancement of slow Ca channels and/or activation of ${\beta}-adrenergic$ receptors in the heart. At this moment it is difficult to explain the exact mode of action of ambrein and the studies dealing with Ca channel blocker and adrenergic blocker followed by ambrein may help to define the factors which contribute to its positive inotropic effects.

• Journal of Biomedical Engineering Research
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• v.40 no.1
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• pp.32-37
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• 2019

In this study, we designed a blending algorithm for rate adaptive pacing for cardiac pacemaker. Generally, rate adaptive pacing (RAP) is applied to patients whose heart rate does not rise during exercise for chronotropic incompetence (CI) patient. It is very important to develop an algorithm for RAP that can be properly applied to CI patients. In order to design an RAP algorithm we used dual sensors. Firstly, we designed a bio-signal measurement system based on the dual sensors, which are accelerometer and respiratory system. Secondly, we conducted treadmill test for the simulation experiment while using 3-lead ECG as reference. Finally, we designed a blending algorithm based on activation state of the dual sensors. The proposed blending algorithm was subdivided into three sections based on the accelerometer signal, which are rapidly increased section (W1), hardly changed section (W2), and decreased section (W3). Each weight is set aside for each section. To evaluate this algorithm, ten healthy adult males were participated. The correlation and Root Mean Square Error between the proposed algorithm and the reference were compared, and shown to be r=0.88 and 2.82 bpm, respectively. These results show that the proposed blending algorithm of dual sensors enables proper tracking of the heart rate during exercise. Also, it shows the possibility that the proposed blending algorithm can be applied to improve quality of life of the chronotropic incompetence patient.

• The Korean Journal of Pharmacology
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• v.5 no.1
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• pp.35-38
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• 1969

1.On isolated atrial preparation of frog, effects of sympathomimetic amines were investigated. 2. Isoproterenol, epinephrine, norepinephrine, and phenylephrine produced positive chronotropic and inotropic effects. The relative potencies for the effects of these agents were: isoproterenol > epinephrine> norepinephrine> phenylephrine. Methoxamine had no effects or depressed the atria. 3. Pronethalol antagonized the positive effects of these adrenergic agents competitively. 4. Regitine did not affect the effects of these agents. 5. These data indicate that the adrenergic agents activate the atrial tissue of the frog via stimulation of adrenergic beta-receptor.