مجله فیزیولوژی و فارماکولوژی ایران
پیاپی 3 (پاییز 1396)

Ventricular fibrillation is one of the main causes of sudden death. In order to evaluate the efficacy and mechanism of anti-arrhythmic drugs, various experimental models of arrhythmia have been developed. In the present study some in vitro models of ventricular arrhythmia in rat isolated heart are presented. Furthermore, efficacy of a smart ablation protocol to suppress ventricular rate is examined.

Five groups of 5 Wistar rats were used in this study. In group I, ventricular fibrillation (VF) was induced in the isolated heart by stepwise increased electrical stimulation (0-5 mA). In group II, VF was induced by stepwise increase in end diastolic pressure (25-100 mmHg). Group III (computerized VF model), computerized electrical stimulation was executed during 2 s in the range of 25-125 ms by AV node pack software. Group IV (hypokalemia-induced VF), VF was induced by diminution of potassium to 2.5-2.9mM in Krebs Henseleit solution. Group V, it was same as group III but smart ablation of the left ventricle was carried out by 110 volt DC power to terminate the VF.

Premature ventricular beat, ventricular tachycardia and VF were successfully induced in the first 4 groups. The minimum and maximum threshold of arrhythmia was observed in groups II (0.1 ± 0.07 mA) and III (1.2 ± 0.05 mA), respectively. The longest duration of arrhythmia induced by hypokalemia (240 ± 45 s), while the shortest one provoked by electrical stimulation (10 ± 4 s). The maximum dominant frequency of arrhythmia was observed in group III (14.9 ± 1.2 Hz), while the lowest dominant frequency was related to group I (7.1 ± 1.6). The mean number of ablation was 20 ± 3 and VF terminated in 10% of all arrhythmias.

Experimental arrhythmia can be induced in rat isolated heart by the all 4 protocols. However, increasing end diastolic pressure and hypokalemia are the most efficient methods for induction of ventricular arrhythmia. Left ventricular ablation by using DC voltage and AV node pack software is a useful method to terminate ventricular arrhythmias.

Post-traumatic stress disorder (PTSD) symptoms and pain can be appeared repeatedly following traumatic events. Although in acute stress condition, pain perception significantly covered by stress, few studies have discussed the changes in pain perception in a PTSD stress conditioning. In the present study, changes of facial acute pain and allodynia have been investigated in an animal model of PTSD.

Male Wistar rats were divided to two groups as control and under stress. PTSD was induced by single prolonged stress (SPS) method and confirmed by elevated plus maze (EPM) and rats plasma corticostrone levels. Acute facial pain and allodynia were evaluated by the eye wiping test and von frey test in the experimental groups.

SPS rats spent less time and made a fewer entries into the open arms of EPM (p < 0.05). The corticostrone level was significantly decreased in Stress + DEXA group compared to the Control + DEXA (p < 0.05). The number of eye wiping was significantly decreased in SPS-induced rats compared to the control (p < 0.001). The response threshold of applying von frey filament in face of SPS-induced rats was significantly increased compared to the control (p < 0.001).

Acute pain perception and allodynia of face area of rats was reduced in SPS-induced animals. Increased endogenous opioids in PTSD condition may lead to this observation.

Neuropathy exists in many diabetic patients. The role of Periaqueductal Gray (PAG) region in pain modulation has long been investigated. Opioid and transient receptor potential vanilloid 1 (TPRV1) receptors are distributed in PAG. In this study, the role of intra-PAG injection of capsaicin on morphine analgesia was investigated in diabetic rats.

Twenty-four male Wistar rats (200-250g) were used in this study. Diabetes mellitus was induced by single i.p. injection of streptozotocin 60 mg/kg. Using stereotaxic surgery, a guide cannula was implanted in PAG. Twenty-eight days after STZ administration, neuropathy was confirmed by Von frey and hot plate tests. On day 29, morphine (5 mg/kg) was injected subcutaneously to diabetic rats. Capsaicin (10 nmol/µl) was injected into PAG 15 min later. Tail flick test was performed 5 min thereafter. Tail-flick latency was measured at 15, 30, 45 and 60 min after capsaicin administration.

Von frey and hot plate tests confirmed the hyperalgesia in diabetic rats. Capsaicin microinjection increased morphine analgesia at 15, 30, 45 and 60 minutes after injection in diabetic rats.

It seems that activation of the TRPV1 receptors in PAG potentiates antinociceptive effect of morphine in diabetic rats. This study confirmed evidences indicating the interaction between capsicinoid and opioidergic systems in pain analgesia regulatory system.

Spatial memory and learning deficits are the most visible symptoms of transient cerebral ischemia. Cortex and hippocampus are sensitive against cerebral ischemia. Oxidative stress and inflammation are involved in the pathological process after cerebral ischemic injury. Evidence indicates that minocycline has antioxidant and anti-inflammation effects. In this study the effect of minocycline on memory deficit after transient cerebral ischemia in rat was investigated.

Cerebral ischemia was induced by a transient 20 min bilateral occlusion of common carotid artery (BOCCA) of rat. A total of 60 male Wistar rats weighing 250-300 g were divided into 6 groups. Three groups of rats were evaluated for each drug administration method (pre- or post-ischemic administration of drug or vehicle). 1. Sham group: rats were subjected to the surgical procedure except for occlusion of common carotid artery and received saline (vehicle) 24 h before, or twice daily (every 12 hours) for 7 days after surgery; 2. Control group: rats underwent transient BOCCA and saline was injected 24 h before or twice daily for 7 days after ischemia; 3. Minocycline group: minocycline (40 mg/kg, i.p.) was injected 24 h before I/R (single dose), or twice daily, for 7 days after I/R. The spatial memory and learning were evaluated using the Morris water maze task.

Pre- or post-ischemic administration of minocycline significantly shortened the escape latency time and the distance traversed to reach the hidden platform. It also significantly increased the time spent in target quadrant compared with the control group. There was no significant change in the swimming speed of rats after I/R in the control and minocycline groups (either pre- or post-ischemic administration) during the first 4 days (trial) and the fifth day (probe test).

This study demonstrated the effectiveness of minocycline in preventing spatial memory and learning deficits induced by cerebral ischemia.

The purpose of this study was to assess effect of cinnamon extract supplementation on VEGF and Endostatin protein level in hind leg muscle of aged rats after one session of exhaustive exercise.

Thirty two aged male Wistar rats were subdivided into four groups randomly: exhaustive exercise (EX, n = 8), cinnamon extract (CE, n = 8), cinnamon extract and exhaustive exercise (CE-Ex, n = 8) and control without exhaustive exercise (n = 8). CE and CE-EX groups received (200 mg/kg) cinnamon extract by intra-gastric intubation for 14 days. CE-EX groups and EX performed an exhaustive running test on a treadmill. In the first 10 min, the animals walked on the treadmill at a speed of 10 m/min to warm up. The speed was then increased by 2 m/min every 2 min, till reaching the maximum speed of 28 m/min. The rats were then anesthetized immediately and 4h after trial, and SOL and EDL muscles were removed. VEGF and Endostatin protein level were measured in the muscles by western blot method. Data were analyzed by independent t-test and one-way analysis of variance (ANOVA).

VEGF decreased immediately (p ≤ 0.05) and increased 4 h after exercise in SOL muscle (p ≤ 0.05) of EX group. Endostatin increased immediately and 4 h after exercise in SOL muscle of EX group (p ≤ 0.05). VEGF decreased and Endostatin increased in SOL muscle of CE group. VEGF/Endostatin decreased in EDL muscle of all groups.

Cinnamon extract supplementation inhibited angiogenesis in CE group in SOL muscle but was not inhibited 4 h after exercise in CE-EX group. The raise in VEGF level 4 h after exercise indicates that exercise can overcome the inhibitory effects of cinnamon on angiogenesis.

The  purpose  of  this  study  was  to  investigate  the  effects  of  acute  aerobic  activity  on   spatial learning and memory in rats.

Thirty six  healthy  male  rats  were  randomly  assigned  to  one  of  three  groups:  physical  activity,  sham,  and  control.  Physical activity group ran 50 minutes daily for two weeks on treadmill. Escape latency, distance moved and time spent in the target zone were measured to assess spatial learning and memory.

No  significant differences  were found between  three  groups  in   the acquisition  phase  (p > 0.05) but  the  physical  activity  group  performed  better  than  the  sham and control  groups  in  probe  test  (p = 0.003).  In  recall  test,  the  physical  activity  group  performed  better  than  the  sham and control  groups  in  both  distance moved (p = 0.004)   and   time spent in the target zone  (p = 0.01).

Results  showed  that  acute  aerobic  activity  improves  spatial  learning  in  rats.  It  seems  that  cardiovascular  fitness  obtained  by  aerobic  activity  is  a  physiological  mediator  that  explains  the  relationship  between  physical  activity  and  improved  cognitive  performance.

Dopamine plays an important role in modulating food intake in the central nervous system. Dopamine receptors are distributed within the hypothalamus with significant expression of D2 receptors in hypothalamic paraventricular nucleus (PVN). D2 receptors are involved in modulation of food intake. Therefore, they might have potential as a pharmacologic target in treatment of obesity. This study was conducted to find if microinjection of the D2 receptor antagonist sulpiride, into PVN can modulate food intake.

A guide cannula was stereotaxically implanted in PVN (coordinates: L:+0.4; DV:7 AP:-1.8 mm) of male Wistar rats weighing 220-250 g. Sulpiride (0.1, 0.3, 0.75, 1.5, and 3μg) or saline were injected into PVN after a 7 day recovery period. Food intake was then measured at one, two and three hours afterward. Moreover, effect of sulpiride (0.1 μg, intra-PVN) on spontaneous activity of animals was measured by Auto vision instrument.

Sulpiride at the doses of 0.1 μg (p < 0.001), 0.3 μg (p < 0.001), 0.75 μg (p < 0.01), and 3μg p < 0.05) significantly decreased food intake in a dose- and time-dependent manner. Sulpiride 0.1μg had no significant effect on the locomotor activity of animals.

Activation of D2 receptors of PVN increases food intake. Intra-PVN microinjection of sulpiride decreases food intake by blocking D2 receptors in this area.

Administration of warfarin, the most common oral anticoagulant, is usually accompanied with limitations. Anticoagulant effect of warfarin has wide inter-patients variations due to pharmacodynamics, pharmacokinetics and especially pharmacogenetics factors. Polymorphisms of VKORC1 gene is one of the genetic factors influencing adjustment of warfarin dosage. In order to better determine the appropriate dosage of the drug, this study was conducted to find out the allele and genotype frequencies of VKORC1 gene in population of Birjand city.

One hundred-fifteen patients who referred to Imam Reza and Vali-asr hospitals of Birjand city for PT and INR tests, were selected for this experimental study. After genomic DNA extraction, all amplified PCR products of VKORC1 were sequenced to determine the genotypes. Statistical analysis was performed using SPSS software.

The average age of patients was 57.7 ± 12.9, 55 were women and 60 were men. Normal, heterozygous and homozygous mutant genotypes of -1639 G>A variant, had a frequency of 40.3%, 30.5%, 17.5%  in men; and 50%, 36.7%, 5% in women, respectively. Regarding 1173C>T variant, normal, heterozygous and homozygous mutant genotypes had a frequency of 38.9%, 38.9%, 22.2% in men; and 52.6%, 40.4%, 7% in women, respectively. Two new mutations as g.3660G> A and g.3565G> T with the frequency of 2.7% and 0.9% in -1639 G>A promoter region of VKORC1 gene were observed.  Finally, -1639G and 1173C alleles had a high frequency (68.1% and 62.6%, respectively) in people of Birjand city.

Our results indicate that there are significant differences in the frequency of VKORC1 genetic variants in people of Birjand city compared to other parts of Iran. The ethnic differences can affect sensitivity to warfarin. Therefore, knowing the genotype of the patients before starting warfarin therapy will help to have a precise and efficient therapy.