Opiate receptor agonists (especially dynorphin - a kappa receptor agonist) have found to increase in the injuried segment of spinal cord. It is known to cause spinal cord damage when injected intrathecally. Nalbuphine is a kappa opiate receptor agonist/partial mu antagonist, and fentanyl is selective mu receptor agonist. To determine the effect of nalbuphine and fentanyl on experimental spinal cord injuries of Spague-Dawley rats (N=125): 1) I determinded the MAC (or ED50) values of enflurane, fentanyl, nalbuphine-enflurane in 65% N2O; 2) produced spinal cord injury model by different epidural ballooning time in the control (enflurane) gmup ; 3) produced spinal cord injuries in the experimental (fentanyl, nalbuphine-enflurane) group. The results were as follows ; 1) The MAC value of enflurane was 1.16+/-0.05%, and the ED50 values of fentanyl were 26.8, 36.2, 39.7, 44.7 ug/kg after 15, 30, 45, 60 min of injection, respectively. Also the MAC values of enflurane with 20 mg/kg nalbuphine were 1.08, 0.99% after 60, 90 min of injection, respectively. 2) We produced the graded spinal cord injuries by different epidural ballooning time. 3) The total neurological scores of fentanyl experimental group were significantly higher than control group on the 10th, 14th, and 21st postinjury day.
Animals ; Dynorphins ; Enflurane ; Fentanyl* ; Nalbuphine* ; Rats ; Receptors, Opioid ; Receptors, Opioid, kappa ; Receptors, Opioid, mu ; Spinal Cord Injuries* ; Spinal Cord*

BACKGROUND: Remifentanil is an ultra-short-acting mu opioid receptor agonist. However, there are few reports of its use in children. Therefore, this study compared propofol-remifentanil anesthesia (PR) with a desflurane-N2O anesthesia (D) in children. METHODS: One hundred children (5-12 years), who were scheduled for a tonsillectomy, were randomly assigned to either Group PR (n=50) or Group D (n=50). After inducing anesthesia with propofol and rocuronium, group PR was maintained with an infusion of propofol and remifentanil. Group D was maintained with desflurane. At the end of surgery all the anesthetics were terminated without tapering. The systolic and diastolic blood pressure, and heart rate were measured upon arrival at the operation room, after induction, after intubation, at the beginning of the operation, 5, 10, 20 minutes after beginning of surgery and the end of anesthesia. RESULTS: There was a significantly lower heart rate in group PR than in group D but there was no significant difference in blood pressure between the two groups. CONCLUSIONS: In children, propofol-remifentanil anesthesia is a well-tolerated method of anesthesia, with a lower heart rate compared with desflurane-N2O based anesthesia.
Anesthesia* ; Anesthetics ; Blood Pressure* ; Child ; Heart Rate* ; Heart* ; Humans ; Intubation ; Propofol ; Receptors, Opioid, mu ; Tonsillectomy*

The mu opioid receptor (MOR) has been regarded as the main site of interaction with analgesics in major clinical use, particularly morphine. The repressor element-1 silencing transcription factor (REST) functions as a transcriptional repressor of neuronal genes in non-neuronal cells. However, it is expressed in certain mature neurons, suggesting that it may have complex and novel roles. In addition, the interactions between MOR and REST and their functions remain unclear. In this study, we examined the effects of morphine on the expression of REST mRNA and protein in human neuroblastoma NMB cells to investigate the roles of REST induced by MOR activation in neuronal cells. To determine the effects of morphine on REST expression, we performed RT-PCR, real-time quantitative RT-PCR, western blot analysis and radioligand binding assays in NMB cells. By RT-PCR and real-time quantitative RT-PCR, the expression of REST was found to be unchanged by either the MOR agonist morphine or the MOR specific antagonist CTOP. By western blot, morphine was shown to significantly inhibit the expression of REST, but this suppression was completely blocked by treatment with CTOP. In the radioligand binding assay, the overexpression of REST led to an increased opioid ligand binding activity of endogenous MOR in the NMB cells. These results together suggest that morphine inhibits the expression of REST in human neuroblastoma cells through a post-transcriptional regulatory mechanism mediated through MOR.
Analgesics ; Blotting, Western ; Humans ; Morphine ; Neuroblastoma ; Neurons ; Receptors, Opioid, mu ; RNA, Messenger ; Somatostatin ; Transcription Factors

OBJECTIVETo explore the role of µ-opioid receptors (MOR) in the central nucleus of the amygdala (CeA) in modulating sucrose solution intake in rats.

METHODSSprague-Dawley rats received intra-CeA injection of MOR agonist DAMGO or saline, and then underwent two bottle choice test between sucrose solution and distilled water. After intake of sucrose solution or distilled water, activated neurons in the CeA were labeled and identified with MOR/Fos-double labeling immunohistochemistry.

RESULTSCompared with saline injection, intra-CeA injection of DAMGO significantly increased sucrose solution intake in rats over a 3-h period. Sucrose solution intake induced significantly more c-Fos and MOR/Fos double-labeled neurons in the CeA than distilled water intake.

CONCLUSIONSThe CeA participates in modulation of sucrose intake in rats, and MOR may partly mediate this mechanism.

Amygdala ; metabolism ; Animals ; Male ; Neurons ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; metabolism ; Sucrose ; metabolism

OBJECTIVE: To investigate the role of zinc-fingers and homeoboxes 2 (ZHX2) in regulating μ-opioid receptor expression in the dorsal root ganglion (DRG) in mice with peripheral nerve injury-induced pain hypersensitivity. METHODS: Forty-eight male adult C57BL6J mice were randomized into 4 groups and subjected to chronic constriction injury (CCI) of the sciatic nerve or sham operation followed by microinjection of a specific small interfering RNA (siRNA) of ZHX2 or a negative control siRNA sequence (siNC) into the DRG. Seven days later, the mice were examined for changes in the hind paw withdrawal frequency (PWF), after which the DRG tissue was collected for detecting the expressions of μ-opioid receptor at the mRNA and protein levels using RT-qPCR and Western blotting. In another experiment, the DRG tissues were collected from 6 mice (21-day-old) for primary culture of the DRG neurons, which were transfected with ZHX2 siRNA or the siNC to observe the changes in the expressions of ZHX2 and μ-pioid receptor. RESULTS: Microinjection of ZHX2 siRNA into the ipsilateral L3 and L4 DRGs significantly reversed CCI-induced μ-pioid receptor downregulation in the injured DRG and alleviated CCI-induced mechanical allodynia in the mice. In the cell experiment, ZHX2 knockdown obviously upregulated the mRNA and protein expressions of opioid receptor in the primary cultured DRG neurons. CONCLUSIONS ZHX2 knockdown in the DRG reverses CCI-induced down-regulation of μ opioid receptor to alleviate periphery nerve injury-induced pain hypersensitivity in mice.
Animals ; Ganglia, Spinal ; Homeodomain Proteins ; Hyperalgesia ; Male ; Mice ; Neuralgia ; Rats, Sprague-Dawley ; Receptors, Opioid, mu

Distribution of A118G single nucleotide polymorphism (SNP) in the mu-opioid receptor 1 gene (OPRM1) differs with ethnicity. We assessed the distribution of this SNP in Korean women with breast cancer and compared it with that in women of other ethnicities with breast cancer. Distribution of SNP genotypes was as follows: 49.8% for AG genotype, 40.6% for AA genotype, and 9.6% for GG genotype. Logistic regression analysis showed a negative association between the presence of the G allele at position 118 of OPRM1 and breast cancer in the studied population (odds ratios [OR], 0.635; p=0.002). However, the AG and GG genotypes were not associated with breast cancer in the studied population (OR, 0.719; p=0.130). The proportions of the AG and GG genotypes of the OPRM1 SNP were higher in Korean women with breast cancer than in those of other ethnicities.
Adult* ; Alleles ; Breast Neoplasms* ; Breast* ; Female* ; Genotype ; Humans ; Logistic Models ; Polymorphism, Single Nucleotide ; Receptors, Opioid, mu ; Retrospective Studies*

Opioid receptor, is classified into three subtypes, mu, kappa and delta, with the mu-type receptor plays important roles in opioid analgesia and opioid addiction. The cDNA encoding mu-type receptor was obtained by RT-PCR from human brain RNA and was cloned into pcDNA3.1(+). The resultant recombinant plasmid pcDNAMORs were transfected into CHO cells by liposome. After PCR identification, the positive clone were treated with agonist and antiagonist were tested for their competence of signal transduction. CHO cells that contained mu-opioid receptor in the expression vector pcDNA3.1(+) acquired naloxone-blockable high-affinity specific binding of morphine and DAMGO. The concentration of cAMP in CHO cells transfected with pcDNAMOR was reduced after binding to morphine and DAMGO, and increased after binding naloxone. These results indicate that the mu-type receptor expreesd on the CHO cell has similar biological property as the nature receptor. The availability of these specific cell lines will facilitate the drug development and promote our understanding the mechanism underlying opiate addiction.
Animals ; Brain Chemistry ; CHO Cells ; Cricetinae ; Cricetulus ; DNA, Complementary ; biosynthesis ; genetics ; Humans ; Receptors, Opioid, mu ; biosynthesis ; genetics ; Transfection

OBJECTIVETo determine the affinity of new opioid receptor ligands to cloned mu opioid receptors stably expressed in CHO cell.

METHODSThe binding characteristics of the opioid ligand [3H] diprenorphine (3H-dip) were studied by cellular biological techniques and radioligands binding in cloned mu opioid receptors stably expressed in CHO cells in saturation binding experiments, and were followed by competition binding experiments with a variety of new synthesized opioid receptor ligands.

RESULTSThe Kd and Bmax of [3H] diprenorphine bound to mu receptors were 1.06 nmol/L and 930 fmol/mg protein, respectively. Competition binding experiments revealed that ligand 3# and 12# displayed much higher affinity than DAMGO and Morphine for the cloned mu opioid receptor. However, the affinities of ligands 2#, 6#, 8# and 9# were lower than DAMGO and Morphine.

CONCLUSIONThe present results suggest that the new ligands 3# and 12# have higher affinity to mu opioid receptors. However, ligands 2#, 6#, 8# and 9# have lower affinity to mu opioid receptors.

Animals ; Binding Sites ; Binding, Competitive ; CHO Cells ; metabolism ; Cloning, Molecular ; Cricetinae ; Diprenorphine ; pharmacology ; Ligands ; Receptors, Opioid, mu ; biosynthesis ; genetics ; metabolism

BACKGROUNDOpioid switching is a therapeutic maneuver to improve analgesic response and/or reduce adverse side effects although the underlying mechanisms remain unknown. The µ-opioid receptor (MOR) has an important role in mediating the actions of morphine and other analgesic agents. This study is aimed at exploring the changes of MOR in the periaqueductal gray (PAG) in rats when morphine is substituted for equianalgesic fentanyl.

METHODSForty rats were randomly assigned to five treatment groups: 7 days normal saline group (N group), 7 days fentanyl group (F group), 7 days morphine group (M group), 7 days morphine and 7 days fentanyl-switching group (MF group), and 14 days morphine group (MM group). Rats repeatedly received subcutaneous injections of morphine sulfate (10 mg/kg) or equianalgesic fentanyl sulfate (0.1 mg/kg) twice daily. Rats' antinociceptive response to thermal pain was evaluated by the tail flick latency assay. MOR mRNA and protein expression in the PAG were measured using RT-PCR and Western blotting analyses respectively.

RESULTSThis study showed that after morphine was substituted with fentanyl on day 8, the tail flick latency (TFL) increased from (3.9 ± 0.4) seconds to (11.4 ± 0.4) seconds. The results also demonstrated that both MOR mRNA and protein expression in the PAG of rats in the MF group were less than that in the M group (P < 0.05) but more than that in MM group (P < 0.05).

CONCLUSIONSEquianalgesic fentanyl was still antinociceptive effective in rats with morphine tolerance, which may be due to the switching from morphine to fentanyl attenuating the decline of MOR expression in the PAG of rats.

Analgesics, Opioid ; pharmacology ; Animals ; Drug Tolerance ; Fentanyl ; pharmacology ; Male ; Morphine ; pharmacology ; Periaqueductal Gray ; chemistry ; RNA, Messenger ; analysis ; Rats ; Rats, Wistar ; Receptors, Opioid, mu ; analysis ; genetics

AIMTo compare the antagonistic effects of 6 beta-naltrexol and naltrexone against morphine analgesia.

METHODSThe effects of 6 beta-naltrexol and naltrexone against morphine analgesia were observed in mouse heat radiant tail-flick assay and in mouse (55 +/- 1) degrees C hot plate test. The displacement of 6 beta-naltrexol and naltrexone on binding to CHO-mu receptor was observed by radioligand binding study.

RESULTS6 beta-naltrexol antagonized morphine analgesia but the potency was (6.1 +/- 1.7)% that of naltrexone. The effective duration of 6 beta-naltrexol was 3-4 times that of naltrexone and the peak time of the response was about 0.5-1 h after s.c. equivalent efficacy dose (ED95) in two models. Like naltrexone, 6 beta-naltrexol was effective by oral administration and the potency ratio of p.o./s.c. was 1/3. As an antagonist to opioid receptor, the displacement of 6 beta-naltrexol was about 12.5% that of naltrexone, which was almost in agreement with the efficacies against morphine analgesia in mouse.

CONCLUSIONCompared with naltrexone, 6 beta-naltrexol was less potent but duration was longer.

Analgesia ; Analgesics, Opioid ; antagonists & inhibitors ; Animals ; Female ; Male ; Mice ; Morphine ; antagonists & inhibitors ; Naltrexone ; analogs & derivatives ; pharmacology ; Narcotic Antagonists ; pharmacology ; Pain Threshold ; drug effects ; Receptors, Opioid, mu ; metabolism