Expression of prostaglandin E_2 receptors in rat hippocampus

BACKGROUND: Prostaglandin E2 (PGE2) can directly regulate toxic injury of hippocampal neurons through participation by its receptor. Increase of excitability of hippocampal membrane and long-term synaptic elasticity are closely related to PGE2, PGD2 and PGF2A. This suggests that PGE2 may be a key molecule of neuronal signal passage and regulate the existence of neurons through its receptor. However, which isoforms of PGE2 receptor expressing in hippocampal neurons is still unclear. OBJECTIVE: To research the subtype expression of PGE2 receptor in hippocampus of rats through mRNA transcription and protein interpretation. DESIGN: Animal studies with random, control and operator and designer double-blind methods. SETTING: University of South Carolina, Animal Center. MATERIALS: Sprague-Dawley rats, aged 12 weeks, weighing 200 g, females 48 and males 48, were selected from Animal Center in South Carolina University. Tri ReagentTM kit was provided by Molecular Research Center, USA. METHODS: The experiment was carried out in Animal Center in South Carolina University from January to December 2005. The expression of the PGE2 receptors was profiled and compared in rat hippocampus using real-time RT-PCR and Western-blot techniques. MAIN OUTCOME MEASURES: Expression of PGE2 receptors in various isoforms of hippocampal neurons of rats. RESULTS: mRNAs of all four EP1-4 subtypes were detected in the hippocampus. Western-blot data showed consistently detectable bands at approximately Mr 50 000 of EP1, Mr 40 000 and Mr 52 000 of EP2, Mr 45 000, Mr 57 000 and Mr 105 000 of EP3, and Mr 46 000 of EP4. CONCLUSION: Identifying four subtypes of EPs heterogeneously expresses in the hippocampus.

Lead Can Inhibit NMDA-,K^+-,QA/KA-Induced Increases in Intracellular Free Ca^(2+) in Cultured Rat Hippocampal Neurons

Objective To examine the effects of Pb2+ on N-methyl-D-aspartate (NMDA)-, K+- and quisqualate(QA)/kainite(KA)-induced increases in intracellular free calcium concentration ([Ca2+],) in cultured fetal rat hippocampal neurons in order to explain the cognitive and learning deficits produced by this heavy metal. Methods Laser scanning confocal microscopy was used. Results The results clearly demonstrated that adding Pb2+ before or after NMDA/glycine stimulation selectively inhibited the stimulated increases in [Ca2+], in a concentration-dependent manner. In contrast, Pb2+ treatment did not markedly affect increases in [Ca2+], induced by an admixture of QA and KA. The minimal inhibitory effect of Pb2+ occurred at 1 μmol/L, and more than seventy percent abolition of the NMDA-stimulated increase in [Ca2+]; was observed at 100 Jμmoll/L Pb2+. Evaluation of Pb2+-induced increase in [Ca2+], response to elevating extracellular concentrations of NMDA, glycine or calcium revealed that Pb2+ was a noncompetitive antagonist of both NMDA and glycine, and a competitive antagonist of Ca2+ at NMDA receptor channels. In addition. Pb2+ inhibited depolarization-evoked increases in [Ca2+], mediated by K+ stimulation(30μmol/L). indicating that Pb2+ also depressed the voltage-dependent calcium channels. Also, the results showed that Pb2+ appeared to be able to elevate the resting levels of [Ca2+|, in cultured neurons, implying a reason for Pb2+-enhanced spontaneous release of several neurotransmitters reported in several previous studies. Conclusion Lead can inhibit NMDA-. K+-, QA/KA-jnduced increases in intracellular [Ca2+], in cultured hippocampal neurons.

AduoLa Fuzhenglin Down-regulates Microwave-induced Expression of β_1-adrenergic Receptor and Muscarinic Type 2 Acetylcholine Receptor in Myocardial Cells of Rats

This paper is aimed to study the effect of ADL on expression of ~z-AR and Mz-AchR in myocardial cells of rats exposed to microwave radiation. Immunohistochemistry, Western blot and image analysis were used to detect the expression of ~I-AR and Mz-AchR in myocardial cells at 7 and 14 d after microwave exposure. The results show that the expression level was higher in microwave exposure group and 0.75 g/（kg.d） ADL group than in sham operation group and significantly lower in 1.5 and 3.0 g/（kg.d） ADL groups than in microwave group. So we have a conclusion that the expression of I^z-AR and Mz-AchR is down-regulated in myocardial cells of rats exposed to microwave radiation. ADL can protect rats against microwave-induced heart tissue injury.

Biodegradable magnesium wire promotes regeneration of compressed sciatic nerves

Magnesium（Mg） wire has been shown to be biodegradable and have anti-inflammatory properties. It can induce Schwann cells to secrete nerve growth factor and promote the regeneration of nerve axons after central nervous system injury. We hypothesized that biodegradable Mg wire may enhance compressed peripheral nerve regeneration. A rat acute sciatic nerve compression model was made, and AZ31 Mg wire（3 mm diameter; 8 mm length） bridged at both ends of the nerve. Our results demonstrate that sciatic functional index, nerve growth factor, p75 neurotrophin receptor, and tyrosine receptor kinase A m RNA expression are increased by Mg wire in Mg model. The numbers of cross section nerve fibers and regenerating axons were also increased. Sciatic nerve function was improved and the myelinated axon number was increased in injured sciatic nerve following Mg treatment. Immunofluorescence histopathology showed that there were increased vigorous axonal regeneration and myelin sheath coverage in injured sciatic nerve after Mg treatment. Our findings confirm that biodegradable Mg wire can promote the regeneration of acute compressed sciatic nerves.

IMMUNOHISTOCHEMICAL DISTRIBUTION OF ERYTHROPOIETIN AND ITS RECEPTOR EXPRESSION IN POSTNATAL RAT RETINA DEVELOPMENT

Objective To investigate the distribution of erythropoietin （EPO） and erythropoietin receptor （ EPOR ） expression in the postnatal rat retina development. Methods Forty-two male Sprague-Dawley rats were divided into 7 groups according to their various postnatal days： postnatal 1 d （D1 group）, 3 d （D3 group）, I week （W1 group）, 2 weeks （W2 group）, 3 weeks （W3 group）, 4 weeks （W4 group） and8 weeks （W8 group） （ n = 6 ）. Single eye was randomly chosen from each rat for the study. The retinal sections were stained with hematoxylin and eosin （HE） and used for the retina development observation. Immunohistochemical staining was used to localize EPO and EPOR expressions in retinas.of differentstages of development, and the expression intensities were determined by an image plus 4 program~~ Results The retinal inner nuclear layer （INL） and outer nuclear layer （ONL） were mixed together and had not yet fully differentiated in D1 and D3 groups. The INL and ONL formed their own independent regions and the outer plexiform layer （OPL） appeared between two layers in W1 group. With the postnatal retinal development, the inner plexiform layer （ IPL ） , rods and cones layer （ RCL ）, and OPL were gradually widened and stabilized in W2 to W3 groups. EPO/EPOR expressions located prominently in the inner part of the postnatal rat developing retinas. The expression of EPO in GCL and INL gradually increased from DI to W4, then the expression decreased in W8. Expression of EPOR in GCL gradually increased from DI to WI , then decreased in W2 ; and it gradually increased again from W3 to W8. Expression of EPOR in INL gradually increased from D1 to W1, then decreased in W2 ; and it continued to decrease from W3 to W8. Expression of EPOR in the external segment of RCL gradually increased from D1 to W8. However, expression in the internal segment of RCL gradually decreased from D1 to W3 , then no obvious expression was seen in the internal segment of RCL in W4 and W8. Conclusion EPO/EPOR expressions locate prominently in the inner part of the postnatal rat developing retina. And EPO/EPOR expressions in the rat retinas exist the dynamic changes during the postnatal retina development period.

The Effect of U50488 on the Cardiac Rhythm and Intracellular Calcium in the Rat Heart.

The effect of U50488, a selective K-opioid receptor agonist, on cardiac rhythm in the isolated perfused rat heart and intracellular calcium ([Ca2+] i) in the single ventricular myocyte were studied. The results showed that U50488 can induce arrhythmias dose-dependently in the isolated perfused rat heart and increase [ Ca2 + ] i in the single ventricular myocyte. The effect of U50488 can be blocked by a selectivek-receptor antagonist, nor-binaltorphimine. The arrhythmogenic effects and the increase of [ Ca2+]i induced by U50488 were blocked by U73122, neomycin and streptomycin, which are selective phospolipase C inhibitors, but not by U73433, the inactive structural analog of U73122. These results demonstrated that the arrhythmogenic effect of cardiac K-receptor is due to activation of phosphoinositol/Ca2+ pathway.

1,25-Dihydroxyvitamin D_(3) effects on the regulation of the insulin receptor gene in the hind limb muscle and heart of streptozotocin-induced diabetic rats

In the present study, we examine the effects of the treatment with 1,25-dihydroxyvitamin D3 [150 IU/Kg (3.75 μg/Kg) once a day, for 15 days] to non-diabetic and streptozotocin-induced diabetic rats. The results indicate that treatment with 1,25-dihydroxyvitamin D3 had minor effects in non-diabetic rats. The same treatment in streptozotocin-induced diabetic rats, although it did not correct the hyperglycemia and hypoinsulinemia induced by the diabetes, caused other actions that could mean beneficial effects on the amelioration of diabetes e.g., it avoided body weight loss, increased calcium and phosphorus plasma levels, and corrected the over-expression of the insulin receptor mRNA species of 9.5 and 7.5 Kb present in the hind limb muscle and heart of these animals. These genomic 1,25-dihydroxyvitamin D3 effects could involve transcriptional mechanisms of repression mediated by vitamin D response elements in the rat insulin receptor gene promoter. Using computer analysis of this promoter, we propose the -249/-235 bp VDRE (5’GGGTGACCCGGGGTT3’) with a pyrimidine (T) in the (+7) position of the3’half-site as the best candidate for negative control by 1,25-dihydroxy-vitamin D3. In addition, posttranscriptional mechanisms of regulation could also be implicated. Thus, computer inspection of the5’untranslated region of the rat insulin receptor pre-mRNA indicated the presence of a virtual internal ribosome entry segment whereas the computer inspection of the3’untranslated region localized various destabilizing sequences, including various AU-rich elements. We propose that through these virtual cis-regulatory sequences, 1,25-dihydroxyvitamin D3 could control the translation and stability of insulin receptor mRNA species in the hind limb muscle and heart of diabetic rats.

Activation of epidermal growth factor receptor mediates myocardial ischemia/reperfusion arrhythmias in anaesthetized rats

Objectives Epidermal growth factor receptor （EGFR）is a receptor protein tyrosine kinase and plays a critical role in the development and function of the heart.Previous studies have demonstrated that EGFR is involved in regulating electrical excitability of the heart.The present study was designed to investigate whether EGFR activation would mediate myocardial arrhythmias induced by ischemia/reperfu- sion in anaesthetized rats.Methods and results Myocardial ischemia/reperfusion arrhythmias were induced by 10 min ligation of the left anterior descending coronary artery,followed by a 30 min reperfusion in anaesthetized rats.Incidence and severity of cardiac arrhythmias were significantly reduced by pretreatment with the EGFR kinase inhibitor AG556.Phosphorylation level of myocardial EGFR was increased during ischemia and at early reperfusion.Intramyocardial transfection of EGFR siRNA reduced EGFR mRNA and protein,and decreased the incidence of ventricular fibrillation induced by reperfusion.Interestingly,tyrosine phosphorylation levels of cardiac Na+ channel(INa) and L-type Ca2+ channel(ICa.l) were significantly increased at corresponding time points to the alteration of phosphorylated EGFR level during reperfusion.AG556 pretreatment countered the increased tyrosine phosphorylation level of Na+ and L-type Ca2+ channels induced by reperfusion.No significant alteration was observed in tyrosine phosphorylation levels of cardiac Kv4.2 and Kir2.1 channels during the cardiac ischemia/reperfusion. Conclusions These results demonstrate for the first time that EGFR plays an important role in the genesis of myocardial ischemia/reperfusion arrhythmias,which is likely mediated at least in part by enhancing tyrosine phosphorylation of cardiac Na+ and L-type Ca2+ channels.

Correlation of expression of preprothyrotropin-releasing hormone and receptor with rat testis development

Objective To investigate the expression regulation of thyrotrophin-releasing hormone (TRH) and TRH receptor (TRH-R), and their role in the development of rat testis.Methods Oligonucleotide primers were designed from the sequences of rat hypothalamus prepro TRH (ppTRH) and pituitary TRH-R cDNA for reverse transcription polymerase chain reaction (RT-PCR). Specific fragments of ppTRH and TRH-R cDNA were cloned and sequenced. Expression plasmids containing ppTRH and TRH-R genes were then constructed, and expression was found in E.coli DH5-α. ppTRH and TRH-R mRNA in the testis was quantitated in RNA samples prepared from rats at different developmental stages by real time quantitative RT-PCR.Results The quantitative analyses demonstrated that no ppTRH and TRH mRNA could be detected at the earliest stage (day 8). ppTRH and TRH mRNA signals were detected on day 15 and increased progressively on days 20, 35, 60 and 90. Conclusion Our results suggest that rat testis could specifically express TRH and TRH-R, and the transcriptions of ppTRH and TRH-R genes in the rat testis were development-dependent. The acquirement of expressed products for ppTRH and TRH-R can be used for further research on the physiological significance of TRH and TRH-R expression in rat testis.

CCK RECEPTOR ANTAGONIST L-365,260 POTENTIATED ELECTROACUPUNCTURE ANALGESIA IN WISTAR RATS BUT NOT IN AUDIOGENIC EPILEPTIC RATS

Cholecystokinin octapeptide (CCK-8) has been shown to be a neuropeptide with potent anti-opioid activity. Previous studies have shown that central administration of nanogram dose of CCK-8 totally abolished morphine analgesia in the rat, an effect mediated by CCK-B receptor in central nervous system. In the present study CCK-B antagonist L-365,260 was injected intracerebroventricularly (icv) to Wistar rats to see its effect on the analgesic effect induced by electroacupuncture (EA) stimulation. A marked potentiation of EA-induced analgesia was observed. The degree of potentiation depends on the frequency of EA used, with a rank order of 100 Hz > 15 Hz = 2/15 Hz>> 2Hz. In a strain of rat with acoustically evoked epileptic seizure (P77PMC rats), an extra-ordinarily strong analgesic effect was produced in response to 100 Hz EA stimulation, which was similar to that in Wistar rats pre-treat ed with L-365,260. However, L-365,260 was not effective in potentiating EA analgesia in P77PMC rats. The results suggest that (1) high frequency EA is more likely to increase the release of CCK-8 in CNS as compared to low frequency EA, and (2) P77PMC rats may have a functional defect of the central CCK neurons in the nature of either a low CCK content or a reduced rate of release of CCK-8 in the CNS.

Effects of Ningdong granule on DA,DRD2,and HVA in a rat model of Tourette's syndrome

OBJECTIVE:Ningdong granule is a traditional Chinese medicine preparation for the treatment of Tourette's syndrome.METHODS:Sixty-four rats were randomly assigned to a control group and three experimental groups,respectively.Rat models of Tourette's syndrome were established via intraperitoneal injection of apomorphine(Apo).The rats in the experimental groups were subsequently intragastrically injected with haloperidol at 10 mg/kg(haloperidol group),Ningdong granule at 370 mg/kg(NDG group),and normal saline(0.9%) at 10 mL/kg(Apo group),respectively.Rat behaviors were observed and recorded on a daily basis.After 12 w,all rats were sacrificed,and sera and striatal tissues were harvested.Homovanillic acid levels in sera,as well as dopamine and dopamine D2 receptor mRNA expression in the striatum,were measured to determine possible mechanisms of Ningdong granule on the dopamine system in a rat model of Tourette's syndrome.RESULTS:Following intervention,stereotype actions of the Tourette's syndrome rats were significantly inhibited in the haloperidol and NDG groups,respectively(P<0.01).Homovanillic levels were significantly greater in the haloperidol and NDG groups,respectively(P<0.05).In addition,dopamine levels were significantly less in the NDG group(P<0.01),and DRD2 mRNA expression was significantly reduced in the haloperidol and NDG groups,respectively(P<0.05).CONCLUSION:Results demonstrated that Ningdong granule effectively inhibited stereotype actions and Tourette's syndrome symptoms by promoting dopamine metabolism,reducing dopamine levels in the striatum,increasing homovanillic acid content in sera,and reducing mRNA expression of DRD2 in the striatum.

Effect of Shengqing capsule on serum cholesterol content and hepatic scavenger receptor class B of rats with cholesterol calculus

Objective To observe the effect of Shengqing Capsule(SC)on serum contents of TC,LDL-C,and HDLC,hepatic scavenger receptor BⅠ(SRBⅠ),and CD36 in rats with cholesterol calculus.Methods

Effect of the change of ghrelin and its receptor on accelerating diabetic encephalopathy by blood glucose fluctuation in GK rats

Objective To explore the the effect of the changes of ghrelin and its receptor(GHSR1a)on accelerating diabetic encephalopathy by blood glucose fluctuation in GK rats.Methods Eight male wistar rats were set as normal control group(NC).16 male GK rats were randomly divided into sustained hyperglycemia group(MS)and blood glucose fluctuation group(MF).MF group