Search published articles


Showing 26 results for Alizadeh

Farshad Alizadeh Mansouri, Fereshteh Motamedi, Fereshteh Fathollahi, Nafiseh Atapour, Saeed Semnanian,
Volume 1, Issue 1 (Spring and Summer 1997)
Abstract

The effects of chronic morphine administration on the development of long-term potentiation (LTP) were investigated at the Schaffer collateral-CA1 pyramidal cell synapses of the rat hippocampal slices using primed-bursts tetanic stimulation. Significant enhancement of orthodromic population spike (OPS) was found for all stimulus intensities after tetanic stimulation. OPS enhancement was greatest when tested with low to mid-range stimulus intensities (25, 50 and 100 µA). There was also significant decrease in OPS delay. These responses were similar in slices from both control and morphine dependent rats. At all delivered stimulus intensities, the amount of LTP of OPS in slices from dependent rats was larger than that of control slices. However, these differences in LTP of OPS were significant at low stimulus intensities. These findings suggest that chronic morphine administration had induced changes in CA1 neurocircuitry which modulated synaptic plasticity during high frequency stimulation and appeared as augmented LTP and also inhibition of LTP decay.
Farshad Alizadeh Mansouri, Fereshteh Motamedi, Fereshteh Fathollahi, Nafiseh Atapour, Saeed Semnanian,
Volume 1, Issue 1 (Spring and Summer 1997)
Abstract

  The effects of chronic morphine administration on the development of long-term potentiation (LTP) were investigated at the Schaffer collateral-CA1 pyramidal cell synapses of the rat hippocampal slices using primed-bursts tetanic stimulation. Significant enhancement of orthodromic population spike (OPS) was found for all stimulus intensities after tetanic stimulation. OPS enhancement was greatest when tested with low to mid-range stimulus intensities (25, 50 and 100 µ A). There was also significant decrease in OPS delay. These responses were similar in slices from both control and morphine dependent rats. At all delivered stimulus intensities, the amount of LTP of OPS in slices from dependent rats was larger than that of control slices. However, these differences in LTP of OPS were significant at low stimulus intensities. These findings suggest that chronic morphine administration had induced changes in CA1 neurocircuitry which modulated synaptic plasticity during high frequency stimulation and appeared as augmented LTP and also inhibition of LTP decay.


Fereshteh Motamedi, Ali Pourmotabbed, Yaghub Fathollahi, Farshad Alizadeh Mansouri, Saeed Semnanian,
Volume 1, Issue 2 (Fall and Winter 1997)
Abstract

  The involvement of NMDA receptors and voltage-dependent calcium channels in augmentation of long-term potentiation (LTP) was investigated at the Schaffer collateral CA1 pyramidal cell synapses in hippocampal slices of morphine dependent rats, using primed-burst tetanic simulation. The amplitude of the population spike and its delay were measured as indices of increase in postsynaptic excitability. D,L-APV and nifedipine were used as an NMDA receptor antagonist and a voltage-dependent calcium channel blocker, respectively. The amount of LTP of the orthodromic population spike (OPS) was higher in slices from dependent rats. Perfusion of slices from control and dependent rats with ACSF containing D,L-APV (25 µ M) and delivering tetanic simulation showed that D,L- APV completely blocked the LTP of OPS in slices from both control and dependent rats, while nifedipine (10 µ M) attenuated the amount of LTP of OPS in dependent slices and had no effect on controls. The results suggest that the enhanced LTP of OPS in the CA1 area of hippocampal slices from morphine-dependent rats is primarily induced by NMDA receptor activity, and the voltage-dependent calcium channels may also be partially involved in this phenomenon.


Sadegh VAlizadeh, Mohammad Reza Zarrindast,
Volume 4, Issue 1 (Spring and Summer 2000)
Abstract

This study was designed to investigate the role of GABAB receptor agents on imipramine-induced antinociception in ligated and non-ligated mice using hot-plate test. The data showed that different doses of morphine (3, 6, and 9 mg/kg) induced a dose-dependent antinociception in ligated and non-ligated mice. However, the opioid response was decreased in ligated animals. Intracerebroventricular (i.c.v.) administration of imipramine (5, 10, 20, and 40 µg/mouse) did not induce antinociception in either non-ligated or ligated mice. However, the induced response in the ligated mice was less than that induced in the non-ligated mice. Intraperitoneal (i.p.) administration of imipramine (10, 20, 30, and 40 mg/kg) induced antinociception in both ligated and non-ligated mice. The responses to the drug were not significantly different in the two groups. Administration of baclofen either i.c.v. (0.125, 0.25, and 0.5 µg/mouse) or i.p. (0.5, 1,2, and 4 mg/kg) induced antinociception. The response to the drug was not significantly different in ligated and non-ligated mice. Intracerebroventricular administration of a lower dose of baclofen (0.125 µg/mouse) with different doses of imipramine (2.5, 5, and 10 mg/kg) potentiated the response to imipramine. This effect was reduced by i.c.v. injection of GABAB receptor antagonist, CGP35348 [P-(3-aminopropyl)-p-diethoxymethyl- phosphinic acid] at a dose of 20 µg/mouse. The higher dose of antagonist (20 µg /mouse) also decreased the response induced by baclofen or imipramine. CGP35348 itself (2.5, 5, 10, and 20 µg/mouse) induced a dose-dependent antinociception with no significant difference in the ligated and non-ligated mice. It is concluded that a GABA receptor mechanism(s) may modulate the antidepressant-induced antinociception.
Abbas Haghparast, Amir-Mohammad Alizadeh, Fereshteh Motamedi,
Volume 12, Issue 2 (Summer 2008)
Abstract

Introduction: Although formalin-induced activity in primary afferent fibers and spinal dorsal ‎horn is well described, the midbrain neural basis underlying each phase of behavior in ‎formalin test has not been clarified. The present study was designed to investigate the nucleus ‎cuneiformis (CnF)‎‏ ‏neuronal responses during two phases after subcutaneous injection of ‎formalin into the hind paw of rat.‎ Materials & Methods: In this study, seventy six male NMRI adult rats, weighing 230-320 g ‎were used. Control group (n=24), which was tested merely for determining spontaneous firing ‎rate of CnF neurons. Saline group (n=15) which received saline (50µl s.c.) instead of ‎formalin into the plantar surface of hind paw after 15 min baseline recording. Formalin group ‎that formalin-induced neural activity of 37 cells simultaneously recorded from the CnF during ‎first phase (0-5 min) and second phase (15-60 min) of formalin test in 5-min intervals, using ‎an extracellular single unit recording technique.‎ Results: The‏ ‏baseline firing rate of neurons in the CnF varied between 1.2 and 39.2 spikes/sec ‎and the average frequency of spontaneous activity over 1 h was 11.8 ± 1.1 spikes/sec. There ‎were three neural clusters after formalin injection. Neurons in cluster 1 (46%) exhibited ‎severe, transient excitatory response in the first (acute) phase while neurons in cluster 2 (35%) ‎exhibited tonic but long-lasting excitatory response in the second (chronic) phase. Cluster 3, a ‎small portion of neurons (about one fifth) which failed to show any evident responses to ‎formalin test. ‎ Conclusion: Our findings suggest that alteration of neural activity and pattern in the ‎spontaneous background of CnF neurons can be mediated a role in the transmission of ‎nociceptive information induced by the peripheral injection of formalin and can be discussed ‎in light of the role of these neurons in nociceptive information processing following ‎peripheral stimuli.‎
Zohreh VAlizadeh, Ahmad Ali Moazedi, Gholamali Parham,
Volume 12, Issue 3 (Fall 2008)
Abstract

Introduction: Zinc is an essential trace element that plays an important role in synaptic plasticity and modulating the activity of CNS and involve in learning and memory. Synaptic vesicle zinc in the hippocampus area exerting modulatory effects on NMDA glutamate receptor. Method: In this experiment the effects of NMDA agonist and antagonist administration intra hippocampus on passive avoidance learning and memory in adult male rats in presence and absence of Zncl2 by step down task has been investigated. Animal divided into 10 group (n=8).Control group, second group received 0.1µg/rat NMDA in 1µlit saline for 4 days. Sham group received saline in the same volume. Forth group received 1µg/rat MK-801 in 1µlit saline 10min before training for 4 days. Sham group received saline in the same volume. Five remain groups received 30mg/kg/day zncl2 in drinking water for 2 weeks. Sixth groups only received 30mg/kg/day zncl2, but others groups (7, 8, 9, and 10) in addition consumption zncl2 received drug and saline in the same condition to 2,3,4,5 groups. Result: our experiment showed that consumption of 30mg/kg/day zncl2 impair learning and memory in adult male rats (P<0.05), while administration of NMDA improve the impairment effects on zncl2 consumption (P<0.05), but administration of MK-801 increasing the impairment effects of zncl2. Concultion: It seems that zinc impaired passive avoidance learning and memory by effects on subunits of NMDA receptor in hippocampus.
Vahid Khori, Ali Davarian, Mohsen Nayebpour, Saeed Saleki, Aref Salehi, Ahmadali Shirafkan, Fakhri Badaghabadi, Mona Pourabouk, Alimohammad Alizadeh, Shima Changizi,
Volume 14, Issue 1 (Spring 2010)
Abstract

Introduction: Recent studies showed that nitrergic system have specific modulatory effects on electrophysiological properties of atrioventricular (AV) node. The aim of this study was to determine the effects of nitric oxide (NO) on the electrophysiological properties of isolated rabbit AV node and to investigate the role of adrenergic and cholinergic receptors in the mechanism of its action. Methods: In our laboratory, an experimental model of isolated double-perfused AV-node of rabbits weighing 1.5-2 kg was used. Specific experimental protocols of recovery, Facilitation, Fatigue and Wenckbach were applied in both control and in the presence of the drug. A total number of 35 rabbits were divided randomly into the following groups (n=7): 1) L-Arg (NO donor) (250, 750 and 1000 μmol), 2) L- NAME, a NO synthesis inhibitor (25, 50 and 100 μmol), 3) L-Arg + L- NAME, 4) Nadolol (1 μmol), 5) Atropine (3 μmol). All data were shown as mean ± SE. The level of statistical significance was set at p<0.05. Results: Our results revealed the depressant effect of L-Arg on the basic and rate-dependent electrophysiological properties of AV-node. L- NAME did not deteriorate the effects of L-Arg on the basic and rate-dependent properties, nevertheless, at high concentration (100 μmol) it had a direct inhibitory effect on the AV-node. Nadolol and atropine could prevent the effects of NO on the basic nodal characteristics and the fatigue phenomenon, respectively. Conclusion: Nitergic system can affect basic and rate-dependent electrophysiological properties of the AV-node through adrenergic and cholinergic receptors.
Vahid Khori, Fatemeh Alizadeh, Sorosh Aminosariyeh, Mona Pourabouk, Mohsen Nayebpour, Aref Salehi, Ahmadali Shirafkan, Saeid Saleki, Fakhri Badaghabadi, Ali Davariyan,
Volume 14, Issue 2 (Summer 2010)
Abstract

Introduction: Recent evidence has indicated that statins can reduce the incidence of both supraventricular and ventricular arrhythmias with various mechanisms. The primary goal of the present study was to determine direct protective role of simvastatin in modifying concealed conduction and the zone of concealment in a simulated model of atrial fibrillation (AF) in an isolated atrioventricular (AV) node in rabbits. Methods: Male Newsland rabbits (1.5-2 kg) were used in all experiments. Stimulating protocols (recovery, AF, zone of concealment) were used to study electrophysiological properties of the node in one group (N=8). All of the stimulated protocols were repeated in the presence and absence of different doses of simvastatin (0.5-10 μm). Results were shown as mean ± S.E. Results: Significant inhibition of the basic properties of the AV node was observed after the addition of simvastatin. Significant prolongation of Wenkebakh index (wbcl) from 138.7±5.6 to 182.1±6.9 and functional refractory period (FRP) from 157.7±5.9 to 182.1±6 msec at the concentration of 10 μM was observed. Maximum efficacy of simvastatin in atrial fibrillation (AF) protocol was observed at the concentration of 3.10 μM, that was accompanied with prolonged HH interval and increased number of concealed beats. Zone of concealment significantly increased at the concentrations of 1.3 and 10 μM. Conclusion: This study shows the protective effect of simvastatin in the prolongation of ventricular beats during atrial fibrillation. The effect of simvastatin in increasing AV-nodal refractory period and zone of concealment are probably the anti-arrhythmic mechanisms of this drug.
Vahid Khori, Saed Saleki, Aref Salehi, Alimohammad Alizadeh, Mona Pourabouk, Fakhri Badaghabadi, Shima Changizi, Mohsen Nayebpour,
Volume 14, Issue 3 (Fall 2010)
Abstract

Introduction: Electrophysiological studies have demonstrated a relationship between aging and atrioventricular (AV) nodal conduction and refractoriness. The aim of the present study was to determine the effects of nodal aging on dynamic AV nodal field potential recording during atrial fibrillation (AF) in rabbit. Methods: Two groups of male New Zealand rabbits (neonatal 2-week-olds and adult 12-week-olds, n=14 each group) were used in this study. Field potential recordings were executed by silver electrodes with a diameter of 100 M. Pre-defined stimulation protocols of AF, zone of concealment (ZOC) and concealed conduction for determination of the electrophysiological properties of the AV-node were separately applied in each group. Results: Results of the study showed that mean ventricular rate (HH) during atrial fibrillation was smaller in the neonatal compared to the adult group (229.1 ± 8.3 versus 198.6 ± 13.1 msec, respectively). Also ventricular distribution conduction pattern showed two peaks in the adult and one peak in the neonatal group. Analyzing the zone of concealment in different rates and after concealed beat indicated that the zone of concealment in neonates were significantly smaller compared with adult rabbits and increasing zone of concealment, which is accompanied with increasing ventricular rate is abrogated in the neonatal group (5 ± 3.3, 12.2 ± 6.3 msec). Conclusion: The results of this study showed that the electrophysiological protective dynamic behavior of the AV node during atrial fibrillation is smaller in neonates compared to adults. Narrower zone of concealment, abrogation rate dependent trend of the zone of concealment and shorter nodal refractoriness can account for the specific nodal electrophysiological properties of neonatal rabbits.
Mitra Yousefpour, Nima Naderi, Mahyar Janahmadi, Amir Mohammad Alizadeh, Fereshteh Motamedi,
Volume 14, Issue 4 (Winter 2011)
Abstract

Introduction: The magnocellular neurons (MCNs) of the supraoptic nucleus (SON) play a crucial role in control of physiological and pathophysiologiccal condition due to two peptides that they synthesize, i.e. Oxytocin (OXT) and Vasopressin (AVP). The activity of MCNs is regulated by a variety of excitatory and inhibitory inputs. Opioid receptors are one of the important receptors in SON synapses. The aim of the present study is to evaluate the effect of acute morphine application on SON synapses and AVP release in rats. Methods: In this study, whole cell patch clamp recording of neurons in rat (70-100 g, 3–4 weeks old) brain slice preparations consisting of SON was used to investigate the effect acute of lowest effective dose of morphine (25μM) administration on spontaneous inhibitory and excitatory post synaptic currents (sIPSCs and sEPSCs) in MCNs. Also, AVP levels were measured in blood samples of rats using ELISA technique after the Morphine injection (30 mg/kg, ip). Results: Bath application of morphine produced an increase in sEPSCs and a decrease in sIPSCs frequencies. Measurement of plasma AVP revealed an increase in hormone levels 45 min after systemic administration of morphine. P-values of less than 0.05 were considered statistically significant. Conclusion: It is suggested that acute administration of morphine stimulates the MCNs and AVP secretion.
Vahid Khori, Mohammad Azadbakht, Mohsen Nayebpour, Amirhosean Jamshidi, Mona Pourabouk, Alimohammad Alizadeh, Fakhri Badaghabadi, Shima Changizi, Maryam Rajaei,
Volume 15, Issue 1 (Spring 2011)
Abstract

Introduction: Despite extensive studies about effects of Crataegus monogyna on cardiovascular diseases yet, a few study has been undertaken antiarrhythmic property of this plant. Aims of the present study were: 1) To determine the protective role of methanolic extract of C.monogyna on the rate-dependent model and the concealed conduction . 2) To explore the role of Na+-K+ A TPase in the protective role of C.monogyna.

 

Methods: In all experiments were used of male New Zealand rabbits (1.5-2kg). Stimulation protocols were used to measure basic and rate-dependent ( recovery, atrial fibrilation and zone of concealment ) AV nodal properties in two groups(N=14) . In the first group all the stimulation protocols before and after different concentrations of C.monogyna extract were repeated (n=7) in the second group (n=7) in the presence of all stimulation protocols Ouabaine(0.05 m M) and extract were repeated. All results have been shown as Mean±SE.

 

Results: Basic and rate-dependent properties of node were inhibited after addition of plant extract of C.monogyna to KerebsHenselite solution . At the maximum concentration of cratagus.m(30 mg/l),WBCL cycle longth is increased significantly from 156.5±3.4 to 173±5.8 ms and nodal functional refractory is prolonged from 164.4±4.1 to 182.7±3.8 ms(P < 0.05).Was recorded Significant decreases of ventricular rhythm in both selective concentrations of plant. The depressent electrophysiologic effect of C.monogyna on the AV node did abolish inhibt by ouabaine.(Selective inhibitore Na+-K+ A TPase Enzyme ).

 

Conclusion: All results are indicating the potential anti-arrhythmic and protective effects of C.monogyna . The effect of plant in increasing nodal refractory period and widen concealment zone might be the major mechanism of this plant. The protective role of cratagus.m does not related to the Na+-K+ A TPase activity.


Vahid Khori, Alimohammad Alizadeh, Mahsa Niknam, Hamid Reza Moheimani, Hamid Yazdi, Mona Pourabouk, Fakhri Badaghabadi, Shima Changizi, Mryam Rajaei, Mohsen Nayebpour,
Volume 15, Issue 2 (Summer 2011)
Abstract

Introduction: Developmental changes in atrioventricular nodal conduction time and refractoriness have been shown in several studies. Prevalence of atrioventricular nodal reentrant tachycardia (AVNRT) is clearly age-dependent. The purpose of this study was to determine developmental changes of basic and frequency-dependent electrophysiological properties of the atrioventricular node (AV-node) in neonatal and adult rabbits. Methods: In this study, the effects of increasing age on the basic and rate-dependent properties of isolated perfused AV-node were analyzed in neonatal (2-week-old) and adult (12-week-old) New Zealand rabbits. Specific stimulation protocols of recovery, facilitation and fatigue were separately applied in each group (n=7). Unipolar extracellular field potential was recorded by a silver electrode (100 M). Results: The results showed that the basic nodal properties (ERP, FRP, WBCL and AHmax) were significantly shorter in neonates compared to the adult group. The magnitude of fatigue was also decreased in the neonatal group compared to control (18.9 ±3.3 vs. 11.1 ± 1.2 msec). Time constant of recovery of the adult group was significantly higher than the neonatal group (P<0.05). Conclusion: The results of this study showed that nodal basic and frequency-dependent properties are age-related and different developmental changes of slow and fast pathways are responsible for this behavior and may reveal the grater susceptibility of AVNRT in young adults compared to infants.
Vahid Khori, Sepideh Shariatnejad, Alimohammad Alizadeh, Hamidreza Yazdi, Mona Pourabouk, Fakhri Badaghabadi, Hamid Reza Moheimani, Shima Changizi, Maryam Rajee, Mohsen Nayebpour,
Volume 15, Issue 2 (Summer 2011)
Abstract

Introduction: Recent studies have shown acute cardioprotective effects of cyclosporine. The aim of the present study was to determine the protective role of cyclosporine on the model simulated the rotational nodal arrhythmia (AVNRT) by using extracellular field potential recordings of isolated atrioventricular-node (AV-node) of rabbit. Methods: This study was performed on isolated double-perfused AV-node of male New Zealand rabbits (1.5-2.5 kg) in one group (n=7). Basic and rate-dependent stimulation protocols (recovery, facilitation, fatigue) and arrhythmia threshold (index of refractoriness) and % Gap incidence were measured for assessment of electrophysiological properties of the AV- node. All stimulation protocols were repeated in control step and in the presence of various cumulative concentrations of cyclosporine (0.5 - 10 μm). Results: Cyclosporine prolonged the effective refractory period from 114.3±7.9 to 142±7.3 msec at the concentration of 10 μm. It also prolonged the functional refractory period from 162±3.3 to 178.6±5 msec and increased the time of Wenckebach at the concentrations of 5 - 10 μM. Various concentrations of cyclosporine increased fatigue and reached a significant level at 10 μm. Gap incidence was 82%, 16.6% and 20% in the control and treatments with 0.5 and 10 μm of cyclosporine, respectively. Conclusion: Block of MPTP by cyclosporine caused inhibition of basic and rate-dependent properties of atrioventricular node. Cyclosporine, by raising the threshold of arrhythmia, could be possibly considered as an anti- AVNRT drug.
Vahid Khori, Alimohammad Alizadeh, Ameneh Navaiyan, Mohsen Nayebpour, Mona Porabouk, Fakhri Badaghabadi, Shima Changizi, Maryam Rajaei, Hamidreza Moheimani, Hamidreza Yazdi,
Volume 15, Issue 3 (Fall 2011)
Abstract

Introduction: The aim of the present study was to determine direct effects of NO modulation on protective electrophysiological properties of atrioventricular node (AV node) in the experimental model of AF in rabbit. Methods: Isolated perfused rabbit AV nodal preparations were used in two groups. In the first group (N=7), LNAME (50μM) was applied. In the second group (N=12), different concentrations of L - argenine (250 μM - 5000 μM) were added to the solution. Programmed stimulation protocols were used to quantify AV nodal conduction time, refractoriness and zone of concealment. AF protocol was executed by software with coupling intervals (ranging from 75 – 125 msec). Results: L-NAME had depressive effects on basic AV nodal properties. L-Arginine (250μM) had direct inhibitory effects on nodal conduction time, Wenckebach and refractoriness. Significant increases in the number of concealed beats were induced by L-Arginine (500 μM ). Number of concealed beats were increased from 700.7 ± 33.7 to 763 ±21 msec (P<0.05). Trend of zone of concealment prolongation in a frequency-dependent model was abrogated by Larginine (250, 5000 μM). Conclusion: NO at low concentration (in the presence of L-NAME) had facilitatory role on AV nodal properties, but at high concentration (in the presence of L-arginine) enhanced protective role of AV node during AF. Biphasic modulatory role of NO may affect protective behavior of AV node during AF.
Ali Mohammad Alizadeh, Mahdieh Faghihi, Vahid Khori, Maryam Mohsenikia,
Volume 15, Issue 4 (Winter 2012)
Abstract

Introduction: Cardiac preconditioning represents the most potent and consistently reproducible method of rescuing heart tissue from undergoing irreversible ischemic damage. The aim of the present study was to evaluate oxytocin (OT) induced cardioprotection and its signaling pathways on lactate dehydrogenase (LDH) and creatine kinase-MB isoenzyme (CK-MB) in the anesthetized rats. Methods: Eighty-four rats were divided into fourteen groups. Animal’s hearts were subjected to 25 min ischemia and 2 h reperfusion (I/R). Oxytocin (0.03 μg/kg) was used 25 min prior to ischemia. Atosiban, an OT receptor antagonist (1.5 μg/kg), 5-hydroxydecanoic acid, an inhibitor of mitochondrial ATP-dependent potassium channel (10 mg/kg), atractyloside, an opener of mitochondrial permeability transition pores (5 mg/kg), chelytraine, a protein kinase C inhibitor (5 mg/kg) and N-acetylcysteine, a reactive oxygen species scavenger (200 mg/kg) were used 10 min prior to OT administration. Then, LDH and CK-MB levels in plasma were measured. Results: OT administration significantly decreased CK-MB and LDH levels compared to I/R group. Administration of atosiban, 5-hydroxydecanoic, atractyloside, chelytraine and N-acetylcysteine abolished the cardiac preconditioning effect of OT. Conclusion: The present study demonstrates that oxytocin cardioprotective effects are complex and its signaling pathways may mediate through mKATP channels, mPTP, PKC activation and increase ROS.
Vahid Khori, Samaneh Naeimipour, Alimohammad Alizadeh, Ali Haeri Rouhani, Mona Pourabouk, Fakhri Badaghabadi, Maryam Rajaei, Sepideh Shariatnezhad, Hamidreza Moheimani, Saeed Saleki, Mohammad Ali Zeyghami, Mohsen Nayebpour,
Volume 15, Issue 4 (Winter 2012)
Abstract

Introduction: Previous studies have indicated a relationship between MPTP pore and AV nodal rate-dependent properties. The aim of present study was to determine acute direct effects of cyclosporine on extracellular field potential of isolated rabbit AV node during experimental atrial fibrillation. Methods: In one group of male New Zealand rabbits (1.5-2.5 kg) cumulative concentrations of cyclosporine (0.5 – 10 m) were applied on isolated perfused atrio-nodal preparation (n=7). Extracellular field potential recording was sampled during specific stimulation protocols (recovery, zone of concealment and atrial fibrillation) in the presence of drug on electrophysiological properties of AV-node. Results: Cyclosporine significantly decreased the ventricular rate (HH mean) from 231.8 ± 5.7 to 277.4 ± 14.6 msec and functional refractory period during AF (AF FRP) from 138.3 ± 7.5 to 161.2 ± 10.31 msec in control and treated groups, respectively. Effective refractory period during AF (AF ERP) was significantly decreased by cyclosporine 10 mM compared to control group (p<0.05). Conclusion: Cyclosporine-evoked slowing ventricular heart rate during AF was induced by increasing functional refractoy period and ZOC. A possible mechanism can be through blocking of MPT pores.
Vahid Khori, Samaneh Naeimipour, Ali-Mohammad Alizadeh, Mona Pourabouk, Fakhri Badaghabadi, Maryah Rajaei, Sepideh Shariatnezhad, Hamidreza Moheimani, Saeed Saleki, Mohammadali Zeyghami, Mohsen Nayebpour,
Volume 16, Issue 1 (Spring 2012)
Abstract

Introduction: Intranodal pathways of atrioventricular (AV) node play a vital role in the delay of conduction time in response to various atrial inputs. The present study was aimed to determine the frequency-dependent electrophysiological properties of concealed slow pathway according to a functional model of isolated rabbit atrioventricular node preparation after fast pathway ablation. Methods: Experiments were carried out in rabbit isolated heart AV-nodal preparations (N=8) by superfused/perfused mode. Extracellular recording was carried out from transitional cells of posterior and anterior extension of AV-node and upper part of atrium and its bundle. Unipolar silver electrode (100 μm) and direct voltage (100-110 V) was applied to create AV-nodal fast pathway ablation. Results: Minimum conduction time (AHmin) was significantly increased after fast pathway ablation (p<0.05). Fast pathway ablation had no significant impact on fatigue phenomenon but significantly reduced facilitation value (p<0.05). Rate-dependency properties of concealed slow pathway were explained according to functional nodal model. Conclusion: The mathematical functional model accurately simulated frequency-dependent electrophysiological properties of concealed slow pathway after fast pathway ablation, but some modifications are necessary for accurate prediction of nodal behavior in various cycle lengths and in arrhythmia. Concealed slow pathway may be considered as a potential electrophysiological substrate of fatigue and facilitation phenomenon
Mohsen Nasri, Ali Mohammad Alizadeh, Vahid Khori, Sohrab Hajizadeh, Saeed Khodayari,
Volume 16, Issue 4 (Winter 2013)
Abstract

Abstract Introduction: Isolated perfused heart models such as perfusion and superfusion are commonly used for mammalian heart research. However, there are several fundamental limitations in the current techniques. In perfusion model, a suitable cannula is connected to the aorta and the perfusion is retrogradely performed. But, electrode displacement is a potential unwanted event resulted from heart contractions. In superfusion model, atrioventricular node (AV) node area is completely visible and fixed in the tissue bath after appropriate preparation, but tissue ischemia is inevitable due to the absence of cell to cell nutrition. The aim of the present study was to create a novel isolated dual perfusion/superfusion model to be used in heart physiological and pharmacological studies. Methods: The rabbit hearts (n=10) were excised. After preparation of proper sections, the electrodes were attached till the steady state appeared. The stimulation protocols consisting Wenckebach and recovery were then carried out during the isolated dual perfusion/superfusion as well as perfusion and superfusion models. Results: The AV node conduction time was increased from 33±4 ms in the isolated dual perfusion/superfusion heart model to 43±5 and 52±5 ms in perfusion and superfusion models, respectively (P<0.05). In addition, Wenckebach cycle length, effective and functional refractory periods were increased in perfusion and superfusion models compared to the isolated dual perfusion/superfusion model (P<0.05). Conclusion: This study shows the superiority of the isolated dual perfusion/superfusion heart model in tissue nutrition compared to the other common methods of mammalian heart studies.
Mahdih Faghihi , Ali Mohammad Alizadeh, Vahid Khori, Vahid Khodayari , Saeed Moradi ,
Volume 16, Issue 4 (Winter 2013)
Abstract

Abstract Introduction: Occurrence of cardiac arrhythmias and myocardial infarction are two main deleterious events that are caused by ischemia-reperfusion (IR) injury in the heart. Cardiac preconditioning represents the most potent method of rescuing heart tissue from undergoing irreversible ischemic damage. The aim of the present study was to evaluate oxytocin (OT) cardioprotective effects and its signaling pathways in cardiac arrhythmias including ventricular tachycardia (VT) and ventricular fibrillation (VF) in anesthetized rats. Methods: Fifty-four rats were divided into nine groups. Animals’ hearts were subjected to 25 min ischemia and 2 h reperfusion. Oxytocin was used 25 min prior to ischemia. In certain groups, atosiban (an oxytocin receptor antagonist), atractyloside (an opener of mitochondrial permeability transition pore, mPTP) and N-acetylcysteine (a reactive oxygen species scavenger) were used 10 min prior to OT administration. Then, the severity and incidence of cardiac arrhythmias including VT and VF were measured. Results: OT administration significantly decreased the severity and incidence of cardiac arrhythmias compared to the IR group (P<0.05). Administration of atosiban, atractyloside and N-acetylcysteine abolished the cardiac preconditioning effect of OT in cardiac arrhythmia (P<0.05). Conclusion: The present study demonstrates that preconditioning with oxytocin reduced ischemia-reperfusioninduced ventricular arrhythmias and its signaling pathways are probably mediated through mitochondrial permeability transition pore and reactive oxygen species.
Vahid Khori , Ali Mohammad Alizadeh, Bagher Nikyar , Ardeshir Banikarimi, Fakhri Badaghabadi, Ahmad Soltani , Mohsen Nayebpour,
Volume 17, Issue 1 (Spring 2013)
Abstract

Introduction: Endorphins are produced by cardiomyocytes, and exert different effects on the heart. The aim of the present study is to assess morphine effects on extracellular atrioventricular (AV) node field potential pattern and ventricular rhythm of isolated rabbit heart during experimental atrial fibrillation (AF). Methods: Effects of different concentrations of morphine (10, 20, 50 and 100 μM) were assessed by applying basic stimuli protocols involving Wenckebach, recovery, zone of concealment and concealed conduction parameters during experimental atrial fibrillation in isolated rabbit heart. Two-way ANOVA was used to compare the groups. Results: Morphine significantly suppressed basic parameters of AV node. Morphine (100 μM) significantly increased wenckebach index (153.6±3.9 to 169.8±2.9 ms) and functional refractory period (156.9±3.0 to 176.4±3.5 ms) (P<0.05). During experimental atrial fibrillation, morphine nonsignificantly increased mean His–His interval, concealed conduction and zone of concealment (P > 0.05). Conclusion: The present results showed that morphine has concentration-dependent effects on AV node electrophysiological properties. Morphine at low concentrations can decrease nodal conduction and refractoriness of AV node, but in high concentrations causes increased nodal conduction without concealed conduction changes. Dual effects of morphine can explain the unpredictable behavior of heart in cardiac tachyarrhythmias.

Page 1 from 2    
First
Previous
1