Physiology and Pharmacology
Year:2004 | Volume:7 | Issue:2|Papers Count:11

The effects of intraperitoneal injection of N6-cyclohexyladenosine (CHA, a selective adenosine A1 receptor agonist) and 8-cyclopenthyle-l-3-dimethylexanthine (CPT, a selective adenosine A1 receptor antagonist) on entorhinal cortex-kindled seizures were investigated. Fully entorhinal cortex-kindled rats received normal saline (control), CHA (0.06, 0.12 and 0.25 mg/kg) or CPT (0.06 and 0.12 mg/kg) and 15 min later were stimulated at AD threshold. Obtained data showed that intraperitoneal administration of CHA (0.12 and 0.25 mg/kg) reduces entorhinal cortex afterdischarge duration (ADD), duration of stage 5 of the seizure (S5D) and seizure duration (SD) at 15 min post-drug injection. The latency for stage 4 of the seizure (S4L) also increased at these doses. At the dose of 0.06 mg/kg, CHA only reduced S5D. lntraperitoneal injection of CPT increased ADD only at 0.12 mg/kg, but not at 0.06 mg/kg. Pretreatment of animals with CPT (0.06 mg/kg), 5 min before CHA (0.12 mg/kg) blocked the anticonvulsant effects of CHA. Obtained results may indicate that activity of adenosine A1 receptors reduces the severity of entorhinal cortex-kindled seizures.

Although leaf of Vitis vinifera (Vitaceae) has been used in traditional medicine to treat diarrhea, but no clinical and experimental studies have been conducted on its effects on the uterus. It has previously been reported that Vitis vinifera leaf extract reduces the ileum contractions induced by KCl and acetylcholine. The aim of the present study was to investigate the effect of Vitis vinifera hydroalcoholic leaf extract (VLHE) on the uterus of virgin rats. Extract was prepared by macerated method using 70% alcohol for 72 hours and the solvent was evaporated to obtain extract powder. Uterus of virgin rats was suspended in an organ bath containing De Jalon solution at 30 C. Tissue contractility was isometrically recorded under 0.5 g initial tension. Potassium chloride (60 mM) and oxytocin (4 mU/ml) was applied to the tissue in the presence and absence of the extract (0.5, 1, 2, 4, and 8 mg/ml). The contractile force was calculated as percentage or as g/100 mg of tissue. KCI-induced contraction reduced by the extract in a dose-dependent manner (P<0.0001). Application of propranolol (1 M) as a -adrenergic antagonist did not change KCI-induced contraction or extract-induced relaxation in the uterus. After application of oxytocin, extract at a concentration of 4 mg/ml was able to significantly reduce the oxytocin-induced contraction (P<0.0001). Application of the extract (4 mg/ml) 2 minutes before adding the stimulants KCI or oxytocin inhibited the tissue contractions. It seems that VHLE induces its inhibitory effects through the blockade of voltage-dependent calcium channels and adrenergic receptors are not involved in this inhibitory effect.

The nucleoside adenosine is present within cells and body fluids of all living organisms and its production, both intra- and extracellularly, is tightly coupled to energy consumption resulting in increased level of extracellular adenosine. The physiological effects of adenosine are mediated through four pharmacologically and biochemically distinct adenosine receptors (AR), i.e. A1, A2A, A2B and A3. A1 and A3AR generally couple to Gi proteins, whereas A2A and A2B receptors activate Gs proteins. Although the presence of these receptors has been reported in both normal and cancer cells, no data is available regarding breast cancer. Therefore, this study was aimed to investigate the existence and possible role of A3AR in ER+ MCF-7 and ER- MDA-MB468 breast cancer cell lines. The cell lines were cultured in RPMI-1640 medium and incubated with different concentrations of IB-MECA (0.1-100 μM), A3 selective agonist, and MRS-1220 (0.1-10 μM), a highly selective antagonist for different time periods (24-72 hr). MTT viability test was used to evaluate the proliferative and cytotoxic response. Then, mRNA was isolated and reverse transeriptase polymerase chain reaction (RT-PCR) was used. The results showed that IB-MECA at concentrations higher than 10 M results in a significant cell death (p<0.05), which reached the maximum level 48 hr after the experiment in both cell lines. In addition, pretreatment with MRS-1220 at 0.1 and 1 μM prevented the cytotoxic effect of IB-MECA at 30 and 60 μM, indicating that A3 receptor is present on both cell lines. Application of MRS-1220 had no effect when used alone. Further confirmation was provided by the application of RT-PCR method. Since both cell lines were responsive to the A3 agonist treatment and as of the presence of the receptor mRNA in RT-PCR analysis, it is concluded that this membrane receptor exists in the breast cancer cell lines, irrespective of ER status. These data are new and informative, emphasizing the role of A3 receptor in the cell cytotoxicity, which may introduce a new perspective on the mode of action and possible application of adenosine in breast cancer.

Electrical stimulation of neuromuscular system has been used in a variety of research and therapeutic applications. Although tri-polar transcutaneous electrical stimulation (TENS) is commonly used to change motoneuron excitability, but the effect of TENS on synaptic activities through dorsal column stimulation or cutaneous pathways is unknown. So, the aim of this research study was to determine the role of cutaneous receptors in conductance of TENS. For this purpose, 10 healthy non-athlete volunteers were tested in three separated sessions, i.e. control 1 (placebo spray and silent TENS), control 2 (lidocaine spray and silent TENS), and experimental (lidocaine spray and TENS) groups. Tri-polar TENS was used on vertebral column (cathode on T11, one anode 3cm above and another 6cm below the cathode). For evaluation of motoneuron activity, soleus H-reflex and Mh wave recruitment curve were evaluated. We sprayed water (Placebo) and 10% lidocaine on the vertebral column skin under the electrodes for 20 sec. In the experimental session, tripolar TENS on desensitized skin of the vertebral column was applied. TENS was applied for 15 minutes with a frequency of 100 Hz and a pulse width of 300 s. The results showed that Hmax evocation intensity decreases after application of placebo and lidocaine spray (p<0.05). The positive slope of H-reflex recruitment curve also increased after application of placebo and lidocaine spray (p<0.05). Based on the above results, we suggest a theory to explain the change of synaptic activities of spinal cord as follows: Low-threshold cutaneous receptors diminish the pre-synaptic inhibition of Ia afferent fibers and application of TENS on the desensitized skin increases fit L5 slope and decreases fit L3 slope of H-reflex recruitment curve. In this study, since only low-threshold cutaneous receptors were inhibited, therefore, the role of cutaneous receptors in conductance of TENS could not be ignored.

Considering the clinical significance of opioids, especially their application for the treatment of severe painful conditions including cancer pain and the requirement for the synthesis of more specific drugs with lower side effects, this study was conducted to perform a preliminary investigation on six newly developed opioid drugs. Our aim was to introduce drugs that act selectively on the opioid or receptors. Since the inhibitory effect of the opioids on the smooth muscle cells has already been proved, we have decided to investigate the inhibitory effect of new drugs in this family on the contraction of guinea pig ileum and mouse vas deferens. Each drug was tested for 6 times and the results were evaluated through comparing their Ic50 with morphine and with other drugs regarding MVDIc50/GPI Ic Ratio.The results showed that all new drugs have inhibitory effects on the muscle twitch, which indicates their agonistic property. Secondly, the new drugs were more selective for receptors than ones. Third, drug F in guinea pig didn't produce any significant effect in comparison with morphine, but the observed difference for drugs A, B, C, D, and E were significant as compared to morphine. Furthermore, all of them had significant effect on mouse vas deferens in comparison with morphine.

Therapeutic use of biological response modulators in combination with chemotherapeutic drugs may propose a more efficient way for cancer therapy with fewer side effects. However, the related mechanism has not been well understood. γ-interferon is a modulator of biological responses that inhibits the growth of malignant cells and mediates their differentiation. In this investigation, T cell lymphoblastic leukemia-derived cell line (KE-37) was used for studying the synergistic effect of interferon and chemotherapeutic agents.For this purpose, this cell line was grown in tissue culture flasks and transferred to 96 well plates. Various doses of vincristine, methylprednisolone and dounorubicin were added to culture medium and the cells were grown at 370 °C incubator with 5% CO2. Then, 100 IU/ml of -interferon was added to cell culture at different times (at hours 0, 8, 36, and 60). The synergistic effect of γ-interferon and above-mentioned drugs was measured through MTT assay. Our results suggest that γ-interferon could significantly increase the cytotoxic and/or cytostatic effects of vincristine, methylprednisolone, and dounorubicin (p<0.05). In addition, this synergistic effect was more significant when γ-interferon was added 36 and 60 hours after addition of drugs (p<0.05).

Hemophilia is an X chromosome-linked inherited bleeding disorder. Frequent intra-articular and intra-muscular hemorrhage in severe hemophiliacs can cause significant disability. In order to resolve a simple bleeding in a 20-kilogram child, some 500 IU of factor VIII is usually required. The cost of this replacement therapy is enormous, especially for less wealthy countries. Vigorous exercise in normal individuals has been known to increase levels of F.VIII:C and vWF:Ag transiently through β-adrenergic stimulation. The goal of this research study was to investigate the effect of ergometric exercise on F. VIII activity in patients with mild and moderate hemophilia-A. Research studies on this phenomenon have not been reported since 1984. Since the previous studies have mainly been carried out on either healthy individuals or patients with cardiac functional abnormalities, it appears appropriate to further characterize the effect of exercise on the coagulation parameters in patients suffering from bleeding disorders.For this purpose, 10 hemophiliacs (a mean age of 24 years) were exercised on a bicycle ergometer in accordance with accepted protocols for a period of 23 to 46 minutes. We deliberately limited the periods of activity because of the low exercise tolerance of these patients. Venous blood samples were drawn before and at 8 and 45 minutes after the exercise. The results showed that the increase in the activity of F.VIII:C following exercise was very significant among mildly-affected patients, and the reduction in aPTT at 45 minutes after the exercise, the increase in vWF activity 8 minutes after the exercise, and the rise in vWF:Ag in both stages were all significant.It is concluded that ergometric exercise induces a significant increase in F-VIII activity in both mild and moderate hemophiliacs. Establishing a suitable exercise program in patients with hemophilia A not only improves the status of their musculo-skeletal system, but also transiently increases the activity of F-VIII activity. Prophylaxis in severe hemophiliacs could be achieved by means of replacement therapy. Among mildly- or moderately-affected patients, exercise may serve the same purpose and effectively reduce the need for replacement therapy.

The linker histones (H1 or H5), which play a key role in the folding of chromatin, are general repressors of gene expression. Nuclei of the mature chicken erythrocytes (and in some mammalian cells) contain both of them. Although the interaction of H5 with DNA is stronger than that of H1, it does not prevent the transcription of some erythroid-specific genes. It has been shown that some modifications have important role in modulating the interactions of histones with DNA, specially regulating the transcription. Histone acetylation changes the chromatin structure into an active form. It has been suggested that aspirin (ASA) acts as an acetylator of proteins. Also, it has been used as an anti-cancer drug in recent years. In this research study, histone H5 was extracted from chicken erythrocytes using a modified method. Purity of the obtained H5 was detected by SDS-PAGE electrophoresis. Spectrophotometric results showed that ASA optimum concentration for H5 acetylation was 6.5 mM after incubation for 210 min at 27 °C. These results are compatible with our previous results for H1 acetylation using both ASA and acetic anhydride (as a standard acetylator). Also, the fluorometric data showed the quenching of H5 emission due to its acetylation and partial unfolding. The acetylated protein had lower electrophoretic mobility on SDS-PAGE due to the increase of its molecular weight after acetylation. The interaction of acetylated histone H5 with DNA decreased about 15 bpDNA/H5 molar ratios at 50% precipitation in comparison with the normal H5. However, after the addition of ASA to the H5-DNA complex, only about 5 bpDNA/ H5 at 50% precipitation was seen. It can be concluded that histone H5 (like H1) is acetylated by aspirin. Acetylation neutralizes H5 positive charges, modifies its conformation, and reduces its interaction with DNA.

Memory and learning are considered as the most complicated and important processes of behavioral sciences. On the other hand, considering the wide and progressively increasing applications of anesthetic agents all over the world, it is of great importance to have a reasonable knowledge regarding their effects on the memory process and its retrieval. The main purpose of this study was to evaluate anterograde and retrograde effects of isoflurane anesthesia on the memory process. For this purpose, male rats were divided into one control and two treatment groups. All of the groups underwent the training program of single trial passive avoidance learning, and the treatment groups (b and c) were exposed to isoflurane anesthesia (1.4% for 60 min) before and after the learning program. After 24 hours, the memory retrieval test was performed. The results showed that the mean retention latency value (which was considered as total in the control groups and measured as 600 sec) significantly decreases to 139 and 179 sec in groups b and c respectively (p<0.05). It can be concluded that that administration of isoflurane both before and after learning program causes disturbances in retrieval process of memory and also results in anterograde and retrograde amnesia in rats.