Physiology and Pharmacology
Year:2005 | Volume:8 | Issue:2|Papers Count:11

In the present study, the effect of swim stress on morphine-induced tolerance was investigated in mice using formalin test. In this respect, intraperitoneal administration of different doses of morphine (3, 6, and 9 mg/kg) induced a dose-dependent antinociception in both acute and chronic phases of the formalin test. In addition, an exposure to swim stress 2 or 3 times for 3 consecutive days was performed in order to induce tolerance. This exercise decreased morphine-induced antinociception. Meanwhile, morphine administration (25 mg/kg) for 3 days in the presence of swim stress (for two to three times) potentiated tolerance induced by morphine in both phases of the formalin test. Administration of a higher dose of morphine (50 mg/kg) for 3 days in the presence of swim stress did not alter morphine-induced tolerance in both phases of the test. On the other hand, administration of the latter dose of morphine for 3 days in the absence of swim stress decreased morphine-induced antinociception in both phases of the formalin test. It can be concluded that there may be a cross interaction between morphineinduced antinociception and swim stress.

The prevalence of opioid addiction is relatively high in Iran. Since the mechanism of opioid addiction has not been well understood, this social problem is still remained unresolved. In the present study, the effect of nitric oxide within the nucleus accumbens on the acquisition and expression of morphine tolerance was investigated using an unbiased conditioned place preference (CPP) paradigm in male Wistar rats (200-250 g).For this purpose, morphine (2.5, 5, and 7.5 mg/kg) was administered to induce CPP. Seven days after surgery and cannulation, animals received morphine (12.5, 25, and 50 mg/kg, for three consecutive days) in order to develop tolerance to morphine. Administration of low and high doses of nitric oxide precursor L-arginine (0.3 and 3 µg/rat) into the nucleus accumbens on the testing day increased and decreased the expression of morphine incentive tolerance respectively. In addition, intra-accumbens injection of low and moderate doses of nitric oxide synthase inhibitor L-NAME (0.3 and 1 µg/rat) enhanced the expression of morphine incentive tolerance and an injection of a high dose of this drug (3 µg/rat) attenuated the latter response. Meanwhile, low-dose administration of L-arginine (0.3 µg/rat) before morphine (12.5, 25, and 50 mg/kg) had no effect on the development of morphine tolerance. On the other hand, higher doses of L-arginine (1 and 3 µg/rat) decreased the development of morphine tolerance. Furthermore, injection of L-NAME (0.3, 1, and 3 µg/rat) into the nucleus accumbens enhanced the development of morphine tolerance.It can be concluded that nitric oxide within nucleus accumbens may have an important role in the expression and development of morphine tolerance.

Hepatitis B virus (HBV) is considered a global health problem whid. affects 360 millions of people worldwide and about two millions in Iran. Among HBV antigens, the physiological function of HBeAg is still unresolved. In this respect, its presence in positive patients is regarded as a marker of viral replication and it may have roles in pathogenesis and persistence of the disease, while no obvious changes in clinical course of the disease has been observed in negative patients. As a result, availability of this protein with characteristics of the naturally occurred antigen in high amounts and of the same purity is highly required for being. Utilized in medical research and diagnosis. At present, recombinant HBeAg is being produced in different expression systems for various applications. In the present study, by application of a simple expression/purification system in E. coli and with the aim of producing physiologically natural HBeAg, that portion of the gene, which exactly corresponds to amino acid sequence of the blood-borne HBeAg have been isolated and cloned into pQE-30 vector which adds a 6x Histag to the N-terminal of the inserted gene, providing the ability of one step purification method by exploiting Ni-NTA column chromatography. Following restriction analysis and confirmation of recombinant vector accuracy, transformation to E. coli M15 cells and IPTG-mediated induction for protein expression was performed. Analysis of the purified protein by SOS-PAGE, ELISA and Western blotting indicated that obtained recombinant HBeAg had the perfect antigenic properties of authentic HBeAg and addition of the His-tag segment which produces extra epitopes on this antigen had no adverse effect on these properties. The results of this study clearly describe a very simple and efficient system for providing recombinant HBeAg in high yield and purity for diagnostic and physiological research applications.

Erythropoietin was first introduced as a factor of RBC proliferation and differentiation. Since the use of recombinant human eryrthropoietin (rHuEPO) in the treatment of anemic patients has increased in recent years, therefore, much attention has been focused on its effects on the immune system. Therefore, in the present study anti-HLA antibody titer changes in three groups of sensitized rats (20 and 100 IU/Kg) were evaluated following administration of two doses of rHuEPO. For this purpose, rats were presensitized with HLA antigens of human Iymphocytes. In this respect, RHuEPO injected subcutaneously two times a week for a period of six weeks. Antibody titers were measured by microlymphocytotoxicity method. The results showed that rHuEPo significantly decreases anti-HLA antibody titer. This decrease could be attributed to a reduction in the number or activity of T and B lymphocytes. This effect may also be interpreted by different dosages of the drug, treatment duration, and/or the level of previous sensitization of rats.

Dendritic cells (DCs) with the most powerful antigen-presenting capability possess several clinical applications. Various methods for their generation and maturation are recently under investigation. The purpose of this study was to investigate the efficiency of PPD in maturation induction of monocyte-derived DCs and its comparison with TNF-α.For this purpose, immature dendritic cells were prepared by culturing peripheral blood monocytes from healthy volunteers in the presence of IL-4 and GM-CSF. The obtained immature DCs were stimulated by PPD extract and the results were compared with TNT-α. stimulated immature DCs. Morphological characteristics of the cells and their phenotypic markers were used for comparison of the effects of PPD and TNT-α. The expression of CD11c, CD14, CD1a, HLA-DR, and CD83 were studied by flow cytometery and their changes were analyzed.The obtained results showed that the expression of CD 14 decreases during culturing period, while CD83 and HLA-DR increases. The changes of CD II c were not statistically significant. In addition, CDIa level also relatively decreases during maturation. Regarding the morphological changes, the size of the cells increased by the time and longer cytoplasmic projections was obviously observed on the surface of the cells.Considering the obtained results, PPD-stimulated dendritic cells showed the phenotype of mature dendritic cells as indicated by high expression of CD83 and HLA-DR and low expression of CDla. Therefore, similar to TNT-α PPD can induce maturation of DCs and its optimum dose is 150 µg/ml. Introducing and use of this safe bacterial extract as maturation inducer of DCs can improve the new methods for disease immunotherapy by ex-vivo prepared dendritic cells.

There exist some evidences that physical activity through increasing opioid level could have beneficial effects in some diseases. In the present study, the effect of naloxone and various periods of physical activity on the acute and chronic pain were investigated using formalin test model. For this purpose, 84 NMRI adult male rats weighing 200-280 g were used. Physical activity (for 15 minutes, daily) was induced in different groups by rotating treadmill for 1, 2, and 4 weeks. In addition, naloxone (3 mg/kg, i.p.) as an antagonist of opioids was used in groups with no activity and after different periods of physical activity. Response time for licking and biting behavior at two phases of the test (0-5 min as the acute pain and 25-45 min as the chronic pain) was measured after subcutaneous injection of formalin into dorsal paw of the rats. The results showed that physical activity at weeks 1, 2, and 4 decreases the response time in acute and chronic phases of the model in a time-dependent manner, especially for chronic pain. In addition, naloxone (3 mg/kg) increased response time in acute and chronic pains in the presence of physical activity, but this effect was less in relation to the absence of physical activity. These results suggest that part of physical activity-induced analgesia may be mediated through opioid system and the role of other neurochemical systems could not be ignored in this respect.

There are some reports concerning the analgesic effect of the plant Safureja hortensis L. in Iranian traditional medicine. For evaluation of the possible analgesic effect of this plant, the chronic (formalin test) and acute (tail-flick) pain models were used in male rats. Administration of 62.5, 125, and 250 mg/kg (Lp.) of aqueous extract of this plant did not show any effect in the tail flick test. However, these doses of the extract produced significant analgesic effect in the first and second phases of the formalin test (p<0.001).Sodium salicylate (300 mg/kg, Lp.) only induced analgesia in the late phase of the formalin test.It can be concluded that the analgesic effect of the extract is more effective through intraperitoneal route than oral one, the analgesic effect of 250 mg/kg of the extract was more potent than 62.5 and 125 mg/kg of the extract (Lp.) and 300 and 500 mg/Kg of the extract (p.o.) and 300 mg/kg (Lp.) of sodium salicylate, and since aqueous seed extract of Safureja hortensis L. affects both phases of the formalin test, it produces its analgesic effect through central mechanisms. In addition, the analgesic effect of the extract may be attributed to its flavonoid and trepenoid content.

Considering the clinical research in recent years, it has been shown that turmeric (Curcuma longa) is a medicinal plant with beneficial effect in hepatic-related disorders. Based on the importance of poultry industry and toxic agents that may induce disease in broilers, in this research the protective effect of turmeric was evaluated in an experimental model of liver disorder. For this purpose, broilers were pretreated with turmeric (1 mg/Kg B.W.) for 14 days and then treated with acetaminophen (650 mg/kg B.W.) and turmeric in 25-day broilers for 30 days. The results showed that pretreatment with turmeric will lead to a better rate of growth. The evaluation of enzyme values including ALP, GPT, and GOT indicated the hepatic protective effect of turmeric. There is also pathological proof of these results.

The long-chain omega-3 polyunsaturated fatty acids, especially eicosapentaenoic (EPA, 20:5) and docosahexaenoic acids (DHA, 22:6) are critical in prenatal formation and function of brain cells and the retina of the eye. Marines, especially cold water fishes are good sources of both EPA and DHA.Since milk is a natural compound that plays an importance role in human and animal nutrition, the present study was undertaken to examine the effects of fish oil on the quality improvement of cow milk fatty acids by feeding various amounts (100, 300 and 500 ml) of fish oil to dairy cattle. The finding of the present study showed that administration of fish oil improves the quality of fatty acids in milk so that the concentration of unsaturated fatty acids increases following fish oil supplementation, while the concentration of saturated fatty acids decreases, especially after consuming 300 ml regimen. Also, the concentration of alpha linolenic acid (an omega-3 fatty acid) increased in milk. Therefore, it is recommended to supplement bovine milk with fish oil to improve the quality of its fatty acids.

Neuropathic pain may be due to a primary insult to the peripheral or central nervous system. In this respect hyperalgesia and allodynia are the results of prostaglandin release in the spinal cord. It seems that at earlier stages of injury, COX1 release is more than COX2 isoenzyme. Comparing selective COX2 inhibitors, nimesulide, a highly selective COX2 inhibitor effectively reduces hyperalgesia due to peripheral administration of inflammatory agents like formalin. In this study, the effect of nimesulide and celecoxib was investigated in a neuropathic model of hyperalgesia. For this purpose, male Sprague-Dawley rats (n=18, 150-200 g) were divided into 3 groups, i.e., left ligation (LL, control), Sham-operated, LL+ mentioned drugs. For induction of neuropathic pain, Bennet & Xie (1988) model was used. Nimesulide (1 .25, 2.5. and 5 mg/Kg) and celecoxib (12.7 mg/kg) were used in treated groups. For thermal hyperalgesia 42 °C and 100° C water was used. In addition, acetone and Von Frey Filaments tests were used for cold and mechanical allodynia respectively. Experiments were performed one day before and 1, 3, 5, 7, 10, and 14 days post-injury. For statistical analysis, ANOVA and Tukey"s tests were used and p<0.05 was regarded as significant.The results showed that nimesulide at doses of 2.5 and 5 mg/kg reduce hyperalgesia and allodynia as compared to LL control group. There were also no significant differences between sham and LL+drugs groups. The effect of celecoxib at a dose of 12.7 mg/kg in reducing hyperalgesia as compared to LL control and nimesulide-treated group at a dose of 2.5 mg/kg began later and celecoxib had no anti-allodynic effects in this respect.It seems that nimesulide was more effective than celecoxib in reducing hyperalgesia and allodynia in neuropathic pain condition. In addition, compared to results for chronic inflammatory pain due to formalin administration, nimesuIide was more effective in controlling pain-ensued behavior.