Physiology and Pharmacology
Volume:12 Issue: 2, 2008

(S)- 3,5-Dihydroxyphenylglycine (DHPG) is an agonist for group I metabotropic glutamate receptors. DHPG-induced synaptic depression of excitatory synapses on hippocampal pyramidal neurons is well known model for synaptic plasticity studies. The aim of the present study was to examine the effects of DHPG superfusion on excitatory synapses on pyramidal and fast-spiking GABAergic cells (FS-GABA) of layer II/III of mice visual cortex. Effects of DHPG was examined in visual cortical slices of GAD67-GFP knock-in mice using whole-cell recordings of excitatory postsynaptic potentials (EPSPs) in layer II/III cells evoked by layer IV stimulation. In part of experiments, long term potentiation (LTP) was induced by theta burst stimulation (TBS) paired with postsynaptic depolarization. DHPG induced potentiation of EPSPs of FS-GABA neurons in dose- and use-dependent manners but it has no effect on pyramidal cell excitatory synapses. An antagonist for type 5 metabotropic glutamate receptors (mGluR5) blocked DHPG-induced LTP, while an antagonist for mGluR1 was not effective. This potentiation and TBS-induced LTP occluded each other. Based on important role of FS-GABA cells in cortical neuronal circuit, mGlur5-dependent LTP may play a role in, enhancement or maintenance of synchronized activity of cortical pyramidal neurons.

Resent studies have been shown beneficial effects of hyperoxia pretreatment against ischemia-reperfusion injury in different organs. The aim of the present study was to investigate early and late effects of normobaric hyperoxia (≥95% O2) pretreatment on ischemia-reperfusion injuries in isolated rat hearts. Following 60 and 180 minutes of hyperoxia, rat hearts were isolated immediately (H60 and H180) or 24 hours later (H60/24 and H180/24), and subjected to 30 minutes of regional ischemia followed by 120 minutes of reperfusion. Incidence and severity of ventricular arrhythmias, mechanical function of the heart and coronary flow were assessed during 120 min of reperfusion. LDH and CK release and infarct size were also assessed. Incidence and severity of reperfusion arrhythmias significantly reduced by hyperoxia pretreatment, especially in the early phase of treanment. H180 reduced the incidence of ventricular fibrillation (VF) to 0% vs. 50% of normoxic control, p<0.05). VF duration decreased in H180 group (0 vs. 50±31s in the NC group, p<0.05) and duration of VT decreased in H60 and H180 groups compared to normoxic control group (NC) (1.5±0.7 s and 7.5±2.5 s vs. 17.7±3.3 s respectively, p<0.05). Hyperoxia improves mycardial contractile function and improves coronary flow during reperfusion. Infarct size and enzymes release were also significantly decreased in early and late phase of hyperoxia pretreatment. These results indicate that hyperoxia pretreatment before induction of regional heart ischemia reduces cardiac infarct size and attenuates reperfusion induced arrhythmias in isolated rat heart.

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.‎ 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.‎ 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. 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.‎

Gene expression and purification of luciferases from the firefly, Lampyris turkestanicus, and optimization of cellular ATP measurements were performed. cDNA encoding luciferases from Lampyris turkestanicus was transferred from pQE30 vector into pET28a expression vector and pLtu28 was built. Newly constructed vector was expressed in E. coli XL1 Blue and the recombinant luciferase was purified using Ni-NTA Sepharose column. Enzymatic properties (Km and Vmax) for ATP were measured using luminescence assay. Standard curve of ATP was obtained by Promega ATP detection kit and designed method based on the L. turkestanicus luciferase and ATP serial dilution. Moreover bacterial ATP was measured by Promega kit and designed method using L. turkestanicus luciferase. Results showed that ligation of L. turkestanicus luciferase encoding cDNA into pET28a and transformation of recombinant vector into competent cells was performed efficiently. Using luciferin, positive colonies were screened and cultured. SDA-PAGE showed that recombinant luciferase was efficiently purified by Ni-NTA Sepharose column. ATP standard curve and measurement of bacteria, using Promega and designed method by L. turkestanicus luciferases showed high identity. comparison of developed assay with promega kits in identification of bacterial concentration show its high quality and potent ability in ATP detection.

Feverfew (Tanacetum parthenium) (T.p.) is widely used in folk medicine to treat many diseases. We reported the analgesic effect of T.p. flower and leaf previously. Present study is designed to find the mechanism underlying the anti-nociceptive effect of the aqueous extract of T.p. flower. Based on our previous study, the dose 50 mg/kg i.p. of the T.p. aqueous extract had a potent analgesic effect on mice (NMRI) (20 ± 2 g) in formalin test which is used in the present study also. Here, we study the roles of opioidergic, sertoninergic and α - adrenergic systems on the anti-nociceptive effect of the extract. Animals had pretreated with drugs, 15 min before the extract treatments, including opioid antagonist naloxane (5mg/kg, i.p.), sertoninergic antagonist cyproheptadine (4 mg/kg, i.p.) and α-adrenergic antagonist phentolamine (20 mg/kg, i.p.) separately (each group with n≥6). Saline and extract used as controls. In contrast to extract analgesic effect, pretreatment with naloxan increased the pain sensation in the neurogenic phase of formalin test (p<0.001). Pretreatment with cyproheptadine increased the sensation of pain in both early and late phases (p<0.05). Inhibition of α -adrenergic system was not be able to attenuate the anti-nociceptive effect of the extract. The involvement of sertoninergic system in anti-nociceptive effect of the T.p. extract is proposed by the results. Also the involvement of opioidergic system has to be mentioned in this effect.

Previous studies have confirm the effects of water extract of Crocus sativus on the euphoric and behavioral properties of morphine in mice. In the present study, the effects of intra-accumbal administration of alcohol extract of Crocus sativus stigma on the acquisition and expression of morphine-induced conditioned place preference (CPP) in male Wistar rats (250-300 g) were investigated. This experimental study was conducted on the 78 male rats that were divided in 18 groups (n=6/group). In a pilot study, different doses of morphine (0.5, 1, 2.5, 5, 7.5 and 10 mg/kg) were injected to the animals for evaluation of the drug's ability to induction of place preference. In the second phase of the experiments, the extract of the C. sativus (1, 5 and 10 µg/rat), was administered into the nucleus accumbens shell during or after induction of morphine CPP. Then, CPP were tested in the animals. One-way Analysis of Variance (ANOVA) was proformed for statistical procedure. Administration of morphine (0.5, 1, 5, 7.5 and 10 mg/kg), indcreased the time spend in the compartment paired with morphine (i.e. conditioned place preference-CPP). The increament was significant for the dose 10 mg/kg of morphine. Injection of the same doses of the extract (1, 5 and 10 µg/rat) 5 min before morphine (10 mg/kg) administration, caused a decrease in the time spent in drug-paired side in doses 5 and 10 µg/rat of the extract. In addition, injection of the plant extract (1, 5 and 10 µg/rat) in to the shell part of nucleus accumbens in the test day to the animals in which reveived morphine (10 mg/kg) in the conditioning days decreased the expression of morphine CPP in the animals which was statisticaly significant for doses 5 and 10 µg/rat of the extract. It could be concluded that intra-accumbens shell compartment njection of the alcoholic extract of C sativus can inhibit the acquisition and expression of morphine-induced CPP and shift it to the aversive state in rats.

Anesthetic agents, blood pressure, arterial pH and blood gases have found to influence on the pathophysiology of experimental stroke. Despite, there are very few comparative studies about effects of anesthetic agents in animal model of cerebral ischemia. Therefore, in this study, we investigated the effects of chloral hydrate and pentobarbital anesthesia, as comparative study, on infarct size and motor neurological dysfunctions and physiological parameters in a transient model of focal cerebral ischemia. Twenty-four male Sprague-Dawley rats were divided into chloral hydrate (400 mg/kg ip, n=10) and pentobarbital sodium (60 mg/kg ip, n=14) anesthesia groups. Temporary focal cerebral ischemia was induced by 90 min middle cerebral artery occlusion (MCAO), followed by 23 h reperfusion. Physiologic parameters were measured before and after ischemia. Cortical, striatal infarct volumes and motor dysfunction were determined 24 h after MCAO. Cortical and striatal infarct volume in pentobarbital sodium anesthetized rats were 84±8 and 26±2 mm3 that significantly lower from chloral hydrate group (208±10, 62±2 mm3 respectively, P<0.001). Moreover, neurological motor dysfunction significantly was lower in pentobarbital sodium anesthetized in comparison with chloral hydrate group (P<0.01). Physiologic values were similar between anesthetic groups except mean arterial pressure was significantly greater in the pentobarbital group in comparison with chloral hydrate group (P<0.05). Finding of this study indicated that brain injuries and motor neurological deficits in rat anesthetized with chloral hydrate are higher than from pentobarbital sodium groups in temporary model of focal cerebral ischemia. Thus, the effects of anesthetic agents must be considered in experimental cerebral ischemic studies.

Tamoxifen is a nonstroidal antiestrogen prescribed for treatment of breast cancer. The aim of this study was to investigate the effect of tamoxifen on testosterone level in the serum and sperm count in the epididymis of adult male Wistar rats. Three groups of rats received 200, 400 and 600 µg/kg body weight tamoxifen dissolved in solvent (60% ethanol in physiological solution) for 30 consecutive days. The sham group received the solvent and controls did not receive any drug or solvent. 1, 12 and 36 days after treatment, serum testosterone was measured by radioimmunoassay and sperm numbers in the epididymis were counted. Results showed that testosterone concentration in the serum and sperm count in the epididymis significantly decreased in groups which received tamoxifen compared with the control group. The most profound effects were observed in the first samplings of the group which received 600 µg / kg tamoxifen. These findings indicate that tamoxifen decreases the fertilization ability in adult male rats in a dose dependent manner and this effect disappears after a period of time.

Previous studies have shown that ghrelin inhibits the activity of Hypothalamus –Pituitary – Thyroid (H–P-T) axis. It is also proved that ghrelin increases appetite via Agouti Related Protein and neuropeptide Y pathway, decreases T3 & T4 secretion and inhibits serotonin release from hypothalamic synaptosomes. Serotonin may interact with ghrelin in control of thyroid hormones secretion. Thus, the goal of this study was to determine the influence of the interaction between ghrelin and serotonin agonist on thyroid hormones concentration. This is a suugestive mechanism to determine the effect of serotonin agonist in decreasing the effect of ghrelin. Twenty four male Wistar rats weighing 230-250 g were randomly divided into 3 groups. The groups respectively received 5 nmol ghrelin, 20 nmol serotonin agonist (R)-8-OH-DPAT or 5 nmol ghrelin with 20 nmol (R)-8-OH-DPAT in the volume of 5μl during 3 days via lateral cerebral ventricle. The blood samples were collected from one day before to one day after injections and brain slices were taken to ensure the place of the canulae is right. The plasma were analysed by Radio Immuno Assay technique to determine T3 and T4 concentrations. The results of this experience showed that the (.i.c.v) injection of ghrelin and (R)-8-OH-DPAT respectively decreased and increased the mean plasma concentrations of thyroid hormones significantly (p<0.05), while the interaction of these two substances showed that (R)-8-OH-DPAT can decease the inhibitory effect of ghrelin on thyroid hormones concentration, but this effect is not statistically significant. (p<0.05) This study showed that ghrelin decreased mean plasma concentration of T3 & T4 significantly and serotonin agonist while injected with ghrelin, because of the stronger effect of ghrelin, could not significantly inhibit this effect of ghrelin. (p<0.05)

Using brief episodes of ischemia and reperfusion (IR) prior to a more sustained IR insult – ischemic preconditioning (IPC) – can reduce IR injury of the heart, brain and many other tissues. The purpose of present study was to investigate the effect of 2min ischemic periods on subsequent rat renal IR injury.

Male rat's renal IR injury was investigated in a right nephrectomized model. For this purpose plasma creatinine (Cr) and urea, creatinine clearance, fractional excretion of sodium and histological injury score (Jablonski score; 0-4) were compared among these groups: IR group (40min of renal ischemia – followed by 24h reperfusion), sham group (no IR) and IPC group (3 times of 2min ischemia – 5min reperfusion before 40min of renal ischemia – followed by 24h reperfusion).

Necrosis score was significantly lower in IPC than IR group and cases with Jablonski score = 4 were significantly less frequent in IPC group compared to IR group (11.1% vs. 75%). Plasma Cr and urea, creatinine clearance and fractional excretion of sodium were not significantly different between IPC and IR groups. Cases with plasma urea levels higher than 190 mg/dl and also cases with fractional excretion of sodium beyond 2% were significantly less frequent in IPC group compared to IR group.

Using three times of "2min ischemia–5min reperfusion" before the injurious ischemic insult can reduce rat renal histological injury and relatively attenuate functional renal injury.