Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Biophysical properties of single potassium channel in the brain mitochondrial inner membrane of male rat with Alzheimer’s disease 1 14 EN Adele Jafari Javad Fahanik-babaei Afsaneh Eliassi Reza Saghiri Introduction: Alzheimer’s disease is a progressive neurodegenerative disorder, characterized by impairment of memory and changes in behavior and personality. Recent evidence suggests that mitochondrial channels play important roles in memory disorders. Accordingly, the biophysical properties of a single potassium channel were investigated in the brain mitochondrial inner membrane of rat with Alzheimer’s disease. Methods: In the male Wistar rats (220-250 g), Alzheimer’s disease was induced by intracerebroventricular injection of amyloid beta 1-42 (4μg/μL). After two weeks, the brain mitochondrial inner membranes were extracted. Vesicles were incorporated into lipid bilayer membranes, and single potassium channel properties were investigated. Also, purity of the cell fraction was tested by Western blotting. Protein samples were probed with specific antibodies. Results: Based on our previous data, mitochondrial inner membrane has a potassium channel with a main conductance 93 pS which was 4-AP sensitive and voltage-insensitive at -50 to +40 mV. In the present study, it was demonstrated that the channel conductance was increased to 114 pS in Alzheimer’s disease. In addition, the currentvoltage relationship showed an inward rectification. Western blotting and antibodies directed against various cellular proteins revealed that the extracted material contains only mitochondria. Conclusion: Our data showed that the biophysical properties (gating, conductance and activities) of potassium channel were significantly altered in Alzheimer’s disease. Based on these findings, we propose that the brain mitochondrial potassium channels are involved in Alzheimer’s disease, and it can be considered as a target for therapeutic plans.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Effect of endotoxemia on heart rate dynamics in rat isolated perfused hearts 15 26 EN Mohammad Karim Azadbakht Roham Mazloom Shahram Shahabi AliReza Mani Introduction: Beat-to-beat variation in heart rate shows a complex dynamics, and this complexity is changed during systemic inflammatory response syndrome (e.g. sepsis). It is not known whether or not cardiac pacemaker dynamical rhythm is affected by sepsis. The aim of this study was to investigate heart rate dynamics of isolated heart as well as expression of pacemaker channels (HCN) in a rat model of sepsis (endotoxemia) compared with normal rats. Methods: Male rats weighing 250-300 g were used in this study. Bacterial lipopolysaccharide was injected intraperitoneally (1mg/kg) in the endotoxemia group, and sterile saline in the control group. Three hours after injection, cardiac tissues were isolated and studied using Langendorff apparatus. Heart rate dynamics was assessed by calculating the standard deviation of inter-beat intervals as well as detrended fluctuation analysis (DFA). Quantitative RT-PCR was used to assess HCN expression in atria. Results: Hypoxia had a significantly different effect on heart rate variability in endotoxemic rats compared with controls (P<0.05). DFA analysis showed a linear relationship between logarithm of variance and the logarithm of scale in both endotoxemic and control rats. Atrial expression of HCN1 and HCN2 at mRNA level were significantly higher in endotoxemic rats in comparison with controls (P<0.05). Conclusion: Spontaneous beatings of isolated hearts exhibit a fractal-like dynamics which did not change after global hypoxia and/or endotoxemia. Endotoxemia was associated with altered heart rate variability and increased expression of pacemaker channels that might play a role in pathophysiology of cardiac complications of sepsis.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Modulation of extracellular atrioventricular node field potential pattern and ventricular rhythm by morphine in experimental atrial fibrillation in isolated rabbit heart 27 38 EN Vahid Khori Ali Mohammad Alizadeh Bagher Nikyar Ardeshir Banikarimi Fakhri Badaghabadi Ahmad Soltani Mohsen Nayebpour 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). 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.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Effect of morphine on apoptotic factors caspase-3, PARP and Bax/Bcl-2 ratio in nucleus accumbens in conditioned place preference model in rat 39 50 EN Najmeh Katebi Yasaman Razavi Shabnam Zeighamy Alamdary Shiva Irani Fariba Khodagholi Abbas Haghparast Introduction: Nucleus accumbens (NAc) plays a critical role in neuronal reward circuits that are responsible for motivated and goal-directed behaviors. Some data suggest that morphine induces apoptosis in neurons, while other evidences show that morphine could have beneficial effects against neuronal cell death. This study was designed to evaluate the effect of morphine on apoptosis in the NAc in rat brain by assessing the changes in apoptotic factors. Methods: To investigate the effects of 3 different doses (0.5, 5 and 10 mg/kg) of morphine on induction of apoptotic factors in the NAc after its sub-chronic consumption, conditioned place preference paradigm was used in three groups of rats compared with the control group that received saline, and then the changes in apoptotic factors caspase-3, PARP and Bax/Bcl-2 ratio were assessed by western blot technique. Results: Our results showed that apoptotic factors increase in all three groups treated with morphine. In the nucleus accumbens, morphine induced significant increase (p<0.01) in caspase-3, PARP and Bax/Bcl-2 ratio, in the lowest dose (0.5 mg/kg) compared with the control group that received saline instead of morphine. Conclusion: Increase in apoptotic factors by low dose morphine in the nucleus accumbens of morphine-treated rats shows that morphine can affect the molecular mechanisms which interfere with apoptosis through one kind of its receptors with high affinity. However, with increase in dose of morphine, it seems that other kinds of opioid receptors have been involved which exert some neuroprotective effects of morphine against apoptosis.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Role of a voltage-sensitive calcium channel blocker on inhibition of apoptosis in sensory neurons of cultured dorsal root ganglia in adult rat 51 59 EN Hamid Reza Momeni Mohammad Ali Shariatzadeh Ahmad Hamta Maryam Mirfakhrai Najmeh Eskandari Introduction: Under pathological conditions, abnormal increase in intracellular calcium concentrations is believed to induce cell death. In the present study, a voltage-sensitive calcium channel blocker (loperamide hydrochloride) was used to investigate its role in inhibition of apoptosis in sensory neurons of cultured spinal dorsal root ganglia (DRG). Methods: L5 DRG from adult rats were dissected and divided into three groups: 1. Freshly prepared DRG 2. Control DRG and 3. DRG treated with voltage-sensitive calcium channel blocker (loperamide hydrochloride, 200 μM). The control and the treated DRG were incubated in a culture medium for 72 hours. The DRG were then fixed and sectioned by a cryostat. Morphological and biochemical features of apoptosis in sensory neurons were studied by fluorescent staining (Propidium iodide and Hoechst) and TUNEL methods, respectively. Results: After 72 hours in culture, sensory neurons displayed morphological features of apoptosis. Most of these neurons also appeared as TUNEL positive. At this time period, the application of loperamide hydrochloride not only inhibited both morphological and biochemical features of apoptosis in the sensory neurons but also significantly increased the mean diameter of nucleus in these neurons compared to the control. Conclusion: This study showed that elevated intracellular calcium concentration might be one of reasons for apoptosis of sensory neurons in the cultured DRG.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 New manifestations of electrophysiological remodeling of heart during experimental model of atrial fibrillation in cirrhotic rat isolated heart 60 71 EN Vahid Khori Ali mohammad Alizadeh Hamidreza Moheimani Delaram Shakiba Soroosh Soroosh Aminolsharieh Najafi Shahryar Alizadeh Taghi Amiriyani Ardeshir Banikarimi Mahdi Zahedi Mohamad hadi Molseghi Ahmadreza Dehpour Introduction: The present study is aimed to evaluate electrophysiological remodeling of atrioventricular (AV) node and ventricular conduction during experimental atrial fibrillation (AF) model in isolated heart of cirrhotic rats. Methods: Cirrhosis-induced electrophysiological remodeling was evaluated in 24 isolated retrogradely perfused rat hearts in 2 groups (control and cirrhotic). Cirrhosis was induced after 6 weeks of common bile duct ligation in rats. Extracellular filed potential was recorded from upper atrium and right ventricle. The conduction time, refractoriness and frequency-dependent properties of AV node were characterized by specific stimulation protocols. Experimental AF was simulated by high-rate atrial pacing with random coupling intervals (range 75–125 ms). Results: Nodal conduction time and ventricular responsiveness were significantly increased in the cirrhotic rats compared to the control (95.8 ± 4.2 ms vs. 78.8 ± 3.3 ms) (P< 0.05). Nodal protective function during AF was potentiated with increased R-R interval, concealed beats, ventricular refractoriness and zone of concealment in the cirrhotic group. Cirrhosis evoked rate–dependent ventricular conduction time shortening with different patterns during arrhythmia. Conclusion: Cirrhosis-induced electrophysiological remodeling was shown by increased AV nodal conduction and shortened ventricular conduction. This electrophysiological remodeling may be considered as a new manifestation of cirrhotic cardiomyopathy in the heart, which can change ventricular rhythm during arrhythmia.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Expression of RFamide-related peptide in the dorsomedial nucleus of hypothalamus during the estrous cycle of rats 72 79 EN Mohammad Reza Jafarzadeh Shirazi Farid Pazoohi Mohammad Javad Zamiri Mohammad Saeed Salehi Mohammad Reza Namavar Amin Tamadon Nader Tanideh Afsoon Zarei Kazuyoshi Tsutsui Introduction: RFamide-related peptide (RFRP) is believed to act as an inhibitor of gonadotropin releasing hormone (GnRH) secretion. The aim of the present study was to compare the expression pattern of RFRP neurons in the dorsomedial nucleus of hypothalamus (DMH) at different phases of the rat estrous cycle. Methods: The phases of the estrous cycle were determined in 16 adult female Sprague-Dawley rats using vaginal smears. The rats were divided into five groups: proestrus phase (n=4), early estrus phase (n=3), estrus phase (n=3), metestrus phase (n=3) and diestrus phase (n=3). After transcardial perfusion, their brains were removed and fixed. Diencephalon of each rat brain was sectioned, and DMH-containing sections were stained using an immunohistochemical method. The number of RFRP positive neurons in DMH was counted microscopically. Results: Almost all of the neurons expressing RFRP in the DMH were bipolar. Mean and standard error of the number of RFRP neurons during diestrus (45.8±12.6) and estrus phases (44.7±3.6) were greater (P<0.05) than early estrus (18.8±0.8) and proestrus phases (16.2±2.0). Conclusion: Results confirm a regulatory role for RFRP in DMH in the control of rat estrous cycle.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Evidences for a new cation channel in the brain mitochondrial inner membrane 80 93 EN Javad Fahanikbabaei Adele Jafari Afsaneh Eliassi Reza Saghiri Introduction: Previous studies and our works have indicated several cation channels in the rat brain mitochondrial inner membrane. In this work, we report the single-channel characterization of a cation channel from the rat brain mitochondrial inner membrane incorporated into a planar lipid bilayer. Methods: After removing and homogenizing the adult rat brain, its supernatant was centrifuged in MSE-digitonin, H2O and Na2CO3, separately. Then, mitochondrial inner membrane vesicles were prepared in MSE solution. L-α- Phosphatidylcholine (for preparing membrane lipid bilayer) was extracted from fresh egg yolk. Bilayer lipid membranes were formed in a 150 μm diameter hole. All single channel recordings were filtered at 1 kHz and stored at a sampling rate of 10 kHz for offline analysis by PClamp10. Statistical analysis was performed based on Markov noise free single channel analysis. Results: The channel conductance was 93 pS in 200 mM KCl cis/50 mM KCl trans. The channel open probability appeared voltage-independent at -50 to +40 mV. The main characteristic of channel gating was its marked bursting behavior. Adding 10 mM 4-aminopyridine (4-AP) at positive and negative potentials inhibited the channel activities. Conclusion: These results demonstrate that a new cation channel, present in the brain mitochondrial inner membrane, displays different kinetics and biophysical properties than those classically described for brain mitochondria.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Effect of intracerebroventricular injection of aqueous extract and essential oil of Pulicaria gnaphalodes on PTZ-induced seizures in male rat 94 100 EN Morteza Zendehdel Roza Fallah Ali Baghbanzadeh Maryam Pourrahimi Nabi Shariatifar Sedigheh Garavand Introduction: Pulicaria gnaphalodes contains terpenoids and flavonoids. Referring to the role of benzodiazepine (BZD) receptor ligands as drug candidates in the treatment of epilepsy, anxiety and sleep disturbances, and since natural flavonoids are among these candidates and hold promise as BZD receptor ligands, this research was done to assess the effects of aqueous extract and essential oil of Pulicaria gnaphalodes on seizures induced by pentylenetetrazol (PTZ). Methods: In this research, male Wistar rats (200±20 g) were injected intracerebroventrically by vehicle, aqueous extract (125, 250 and 500 μg) or essential oil (0.125%, 0.25% and 0.5%) (1 μL volume in each), before intraperitoneal administration of PTZ (80 mg/kg) for induction of seizure. Then, onset times of myoclonic (stages 1, 2 and 3) and tonicclonic (stages 4 and 5) seizures were recorded during 20 minutes after PTZ administration. Data were analyzed by oneway analysis of variance. Results: The results of this study showed that aqueous extract and essential oil of Pulicaria gnaphalodes increase initiation time of PTZ-induced myoclonic and tonic-clonic seizures. Conclusion: Aqueous extract and essential oil of Pulicaria gnaphalodes probably have dose-dependent anticonvulsant property.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Effect of vitamin C on tracheal responsiveness and pulmonary inflammation in chronic obstructive pulmonary disease model of guinea pig 101 115 EN Rana Keyhanmanesh Mahdi Ahmadi Sajjad Jeddy Horyeh Bagban Fariba Mirzaei Bavil Mohammad Reza Alipour Mohammad Hossein Boskabady Javad Ashrafi Helan Mohammad Ali Ebrahimi Saadatlou Introduction: In the present study, the prophylactic effect of vitamin C, as a potent anti-oxidant, on tracheal responsiveness to methacholine and ovalbumin, bronchoalveolar lavage fluid white blood cell (WBC) count and differential count, and also lung pathology in chronic obstructive pulmonary disease (COPD) -guinea pigs (cigarette exposed guinea pigs) were examined. In addition, the relaxant effects of theophylline on tracheal chains of guinea pigs were studied. Methods: Twenty four male guinea pigs were randomly divided to three groups control (C group), COPD model of guinea pigs (COPD group) and pretreated group (COPD+ Vit C group). The two first groups were given drinking water alone, and the third group used water containing vitamin C. The relaxant effects of four cumulative concentrations of theophylline were examined by their relaxant effects on precontracted tracheal chains of guinea pig by 60 mM KCl (group 1) and 10 μM methacholine (group 2). Results: The tracheal responsiveness to methacholine and ovalbumine, and WBC count of COPD guinea pigs were significantly higher than those of controls (p<0.05 to p<0.001). The lung in COPD group showed significant pathological changes. The tracheal responsiveness to methacholine and avalbumine and WBC count were significantly decreased in pretreated group compared with the COPD guinea pigs (COPD group) (p<0.05 to p<0.001). In both groups, the relaxant effect of theophylline in the COPD group was lower than the control group (group C) (p<0.05 to p<0.001). Conclusion: These results showed prophylactic effect of vitamin C on tracheal responsiveness and pulmonary inflammation of COPD-guinea pigs.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 Effect of transient inactivation of rostral ventromedial medulla on swim stress induced analgesia in formalin test in rats 116 124 EN Neda Soleimani Elaheh Erami Mehdi Abbasnejad Shamsizadeh Ali Azhdari-Zarmehri Hassan Introduction: Despite significant progress in understanding pain control mechanism, there are numerous questions about central nervous mechanisms underlying stress-induced analgesia. The rostral ventromedial medulla (RVM) in the brainstem integrates a variety of functions, including pain modulation and pain perception. In the present study, we investigated the effect of temporary inactivation of RVM on stress-induced analgesia. Methods: This study was performed using adult male Wistar rats (200-250 gr). Swim stress was induced using a cylinder filled with water (50 cm height, 20±1°C) in which the rats were kept for 3 min. For induction of pain, 50 μL of 2% formalin was injected subcutaneously in the hind paw. For temporary inactivation of RVM, 0.5 μL of 2% lidocaine was injected into RVM. Results: Injection of lidocaine into RVM, before inducing swim stress, potentiated the anti-nociceptive effects of swim stress in phase 1 and phase 2A. In phase 2B swim stresses increased nociceptive scores of formalin test so administration of lidocaine into RVM inhibited the effect of swim stress. Conclusion: The result of this study demonstrated that temporal inactivation of RVM by lidocaine potentiated stress-induced analgesia.

Iranian Society of Physiology and Pharmacology Physiology and Pharmacology 24765236 17 1 2013 3 1 The effect of Co-administrtion of Ascorbic acid and Bromocriptine in nucleus accumbens shell on locomotor activity in male rats by Open Field Test 125 136 EN Mehdi Abbasnejad Fatemeh Shahsevari Background: Ascorbic acid (AA) as a vitamin and neuromodulator is present in the most part of CNS such as nucleus accumbens shell (Acbsh), so the main purpose of this investigation was to evaluated the effect of AA and their Co-administration in Acbsh on anxiety and motor activity of rat by Open Field Test(OFT). Methods: Forty nine adult male Wistar rats (220-270 g) were used into 7 groups: control (intact), sham AA (injected normal salin as AA vehicle), 3 groups of AA (12,24 and 48 μg/rat/side), AA plus Br (24 and 25 μg/rat/side), sham AA plus Br. Drugs were injected (volum= 1µl) for one-day period , locomotor activity and anxiety behavior were assessed. Results: The result showed that Intra-accumbance injection of AA (12, 24 and 48 μg/rat/side) increased locomotor activity and decreased anxiety. Co-administration of AA and Br, showed AA could attenuate the effect of Br. Conclusion: Our findings confirm the role of AA as an effective factor in locomotor activity and anxiety regulation in NAcS.