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

OBJECTIVE: To investigate the relationship between OPRM1 118A/G gene polymorphism and oxycodone analgesic dose in patients with cancer pain. METHODS: DNA sequencing was used to detect the genotypies of OPRM1 118 A/G site in 203 patients with moderate and severe cancer pain, and to compare the relationship between the pain degree and the dose of oxycodone at 3 and 30 days after treatment in patients with different genotypes. RESULTS: The fequencies of AA, AG and GG genotypes at the OPRM1 118 A/G site were 34.78%, 52.70%, and 12.52%, respectively. The dosage of oxycodone in GG genotype was significantly higher than that in AA genotype and AG genotype (15.44±10.19 vs. 10.25±4.53, 10.49±5.26; 89.15±27.69 vs. 43.59±12.19, 48.27±18.79) on the 3 and 30 day after treatment, difference was statistically significant (P< 0.05). CONCLUSION For cancer pain patients with GG genotype of OPRM1 118A/G site, if they need to achieve the same analgesic effect as patients with AA and AG genotype, the dose of oxycodone should be increased.
Analgesics, Opioid ; administration & dosage ; Cancer Pain ; drug therapy ; Dose-Response Relationship, Drug ; Genotype ; Humans ; Oxycodone ; administration & dosage ; Polymorphism, Single Nucleotide ; Receptors, Opioid, mu ; genetics

OBJECTIVETo investigate whether A118G single nucleotide polymorphisms of the µ-opioid receptor (OPRM1) affects epidural patient-controlled analgesia with fentanyl after caesarean section.

METHODSA total of 100 pregnant women (ASA class I or II) scheduled for elective caesarean section were enrolled in this study. All the patients received spinal-epidural anesthesia and were screened for blood A118G polymorphism. Epidural patient-controlled analgesia with fentanyl was provided postoperatively. The pain scores, incidence of nausea and vomiting, and total self-administered epidural fentanyl dose within 48 h postoperatively were recorded.

RESULTSNinety-six patients were finally included in this study. The percentages of the genotypes AA, AG, and GG were 36.5% (35 cases), 46.9% (45 cases), and 16.7% (16 cases), respectively. At 12 and 24 h postoperatively, the pain scores and the total fentanyl dose administered were significantly higher in group GG than in groups AA and AG.

CONCLUSIONA118G single nucleotide polymorphism affects pain relief and total fentanyl dose administered in epidural patient-controlled analgesia after caesarean section. G118 homozygotes have a poorer response to fentanyl than A118 homozygotes or heterozygotes.

Adult ; Analgesia, Epidural ; Cesarean Section ; Female ; Fentanyl ; administration & dosage ; Genotype ; Humans ; Pain Measurement ; Pain, Postoperative ; Polymorphism, Single Nucleotide ; Pregnancy ; Receptors, Opioid, mu ; genetics ; Young Adult

OBJECTIVETo detect the distribution of beta-endorphin and mu-opioid receptors (MOR) in normal skin tissue and scar tissue from healthy volunteers and patients with hypertrophic scar.

METHODSNormal skin samples from 10 healthy individuals and 10 patients with hypertrophic scar, and scar samples from the same 10 patients were investigated. The beta-endorphin and MOR protein in the samples were detected by immunofluorescence (IF). The reverse transcription polymerase chain reaction (RT-PCR) was used to detect MOR mRNA.

RESULTSBeta-endorphin and MOR protein were expressed in all samples. There were no significant differences in the expression of beta-endorphin and MOR protein between normal skin from healthy volunteers and patients with hypertrophic scar (P > 0.05). The expression of beta-endorphin, MOR protein and mRNA in hyperplastic scar was significantly stronger than that in normal skin (P < 0.01).

CONCLUSIONSThe expression of beta-endorphin and MOR is different in normal skin and hypertrophic scar. This maybe the possible reason of scar paresthesia.

Case-Control Studies ; Cicatrix, Hypertrophic ; metabolism ; pathology ; Humans ; RNA, Messenger ; genetics ; Receptors, Opioid, mu ; metabolism ; Skin ; metabolism ; pathology ; beta-Endorphin ; metabolism

BACKGROUNDMu opioid receptor plays an important role in many physiological functions. Fentanyl is a widely used opioid receptor agonist for analgesia. This study was conducted to test the role of mu-opioid receptor on insulin release by determining whether fentanyl affected insulin release from freshly isolated rat pancreatic islets and if small interfering RNAs (siRNA) targeting mu-opioid receptor in the islets could knock down mu-opioid receptor expression.

METHODSIslets were isolated from ripe SD rats' pancreas by common bile duct intraductal collagenase V digestion and purified by discontinuous Ficoll density gradient centrifugation. The siRNA knock-down of mu-opioid receptor mRNA and protein in islet cells was analyzed by semi-quantitative real time-PCR and Western blotting. After siRNA-transfection for 48 hours, the islets were co-cultured with fentanyl as follows: 0 ng/ml, 3 ng/ml and 30 ng/ml for 48 hours. Then glucose-evoked insulin release was performed. As a control, the insulin release was also analyzed in islets without siRNA-trasfection after being co-cultured with fentanyl for 48 hours.

RESULTSAfter 48 hours of transfections, specific siRNA targeting of mu-opioid receptors produced significant reduction of mu-opioid receptor mRNA and protein (P < 0.01). Fentanyl significantly inhibited glucose-evoked insulin release in islets in a concentration dependent manner (P < 0.01). But after siRNA-transfection for 48 hours, the inhibition on glucose-evoked insulin release was reversed (P < 0.01).

CONCLUSIONSRNA interference specifically reduces mu-opioid receptor mRNA and protein expression, leading to reversal of the fentanyl-induced inhibition on glucose-evoked insulin release of rat islets. The activation of opioid receptor induced by fentanyl functions to inhibit insulin release. The use of RNAi presents a promising tool for future research in diabetic mechanisms and a novel therapy for diabetes.

Analgesics, Opioid ; pharmacology ; Animals ; Cell Survival ; drug effects ; Cells, Cultured ; Fentanyl ; pharmacology ; Glucose ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; secretion ; Male ; RNA Interference ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; antagonists & inhibitors ; genetics ; physiology

OBJECTIVETo observe the effects of Jingqianping Granule (JG) on mRNA and protein expressions of mu opioid receptor in the parietal cortex and the frontal cortex, the hypothalamus and hippocampus of premenstrual syndrome (PMS) Gan-qi invasion rats.

METHODSTwenty rats were selected to prepare the PMS Gan-qi invasion model. After modeling rats were divided into the model group and the Chinese herb treated group, ten in each group. Another 10 rats were selected as the normal control group. During the modeling, JG (1.6 g/kg) was given to rats in the Chinese herb treated group by gastrogavage, while equal volume of normal saline (1 mL/100 g) was given to rats in normal control group and the model group. All treatment was performed once daily for five successive days. The mRNA and protein expressions of mu opioid receptor in the parietal cortex and the frontal cortex, the hypothalamus and hippocampus were detected using RT-PCR and Western blot respectively.

RESULTSCompared with the normal control group, the bands of products of MOR mRNA and protein in the parietal cortex and the frontal cortex were relatively weaker in the model group, and the optical density value decreased. The MOR mRNA and protein expressions in the parietal cortex and the frontal cortex relatively decreased. But the bands of products of MOR mRNA and protein in the hypothalamus and hippocampus were relatively stronger and optic value increased. The MOR mRNA and protein expressions in the hypothalamus and hippocampus relatively increased with statistical difference (P<0.01, P<0.05). Compared with the model group, the bands of products of MOR mRNA and protein in the parietal cortex and the frontal cortex were relatively enhanced, the MOR mRNA expression in the parietal cortex increased, the MOR protein expression in the parietal cortex and the frontal cortex increased in the Chinese herb treated group. The bands of products of MOR mRNA and protein in the hypothalamus and hippocampus were relatively weaker. The MOR mRNA and protein expressions in the hypothalamus and hippocampus relatively decreased. The MOR protein expression in the hippocampus decreased relatively with statistical difference (P<0.01, P<0.05).

CONCLUSIONSExpression of mu opioid receptor in brains of PMS Gan-qi invasion rats was regionally specific. Administration of JG showed corresponding regulatory effects.

Animals ; Brain ; metabolism ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Female ; Premenstrual Syndrome ; drug therapy ; metabolism ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; genetics ; metabolism

OBJECTIVETo observe the analgesic effect of electroacupuncture (EA) on collagen-induced arthritis (CIA) rats and its regulating effect on inflammation reaction and the endogenous opioid system of synovial tissues. Methods A total of 30 healthy male Wistar rats were randomly divided into a control group, a model group and an EA group, 10 rats in each one. The chronic pain model of CIA rats was made by cattle type-II collagen in the model group and EA group. Rats in the EA group were treated with EA at "Zusanli" (ST 36) and "Kunlun" (BL 60) for 30 min from 16th day after model establishment, once a day for consecutive 10 days. Rats in the control group did not receive any treatment. Rats in the model group were treated with fixation as the EA group. Threshold of pain, arthritis index, paw swelling were measured before model establishment and 16 d, 20 d, 23 d and 25 d after model establishment. The levels of beta-endorphin (β-END), met-enkephalin (met-ENK), dynorphin A (Dyn A) were measured by radioimmunoassay; the mRNA expressions of mu opioid receptor (MOR), kappa opioid receptor (KOR) and delta opioid receptor (DOR) in synovial tissues of CIA rats were detected by I quantitative polymerase chain reaction (qPCR).

RESULTSCompared with the control group, threshold of pain was reduced (all P<0. 01), arthritis index was increased (all P<0. 01) and paw swelling was increased (all P<0. 01) in the model group on the 16th day, 20th day, 23rd day, 25th day after model establishment. Compared with the model group, the threshold of pain was increased in the EA group (all P<0. 01), arthritis index and paw swelling were reduced (all P<0. 01) on the 23rd day and 25th day after model establishment. Compared with the control group, the level of Dyn A in synovial tissues of CIA rats was increased in the model group (P<0. 01); the mRNA expressions of MOR, KOR and DOR were down-regulated lower than 0. 5 fold of normal level. Compared with the model group, the level of β-END in synovial tissues of the knee joint was increased in the EA group (P<0. 05), and the mRNA expressions of MOR, KOR and DOR in synovial tissues of CIA rats were up-regulated more than 2 folds of normal level.

CONCLUSIONThe intervention of EA on chronic pain of CIA rats is superior, which is likely to be related with effects of EA on anti-inflammation and up-regulation of synovial tissue β-END and MOR, KOR, DOR.

Acupuncture Analgesia ; Acupuncture Points ; Analgesics, Opioid ; immunology ; Animals ; Arthritis, Rheumatoid ; immunology ; therapy ; Cattle ; Chronic Pain ; immunology ; therapy ; Dynorphins ; genetics ; immunology ; Electroacupuncture ; Enkephalin, Methionine ; genetics ; immunology ; Humans ; Male ; Rats ; Rats, Wistar ; Receptors, Opioid, mu ; genetics ; immunology ; Synovial Fluid ; immunology ; beta-Endorphin ; genetics ; immunology

Alcohol dependence is a chronic disorder that results from a variety of genetic, psychosocial, and environmental factors. Relapse prevention for alcohol dependence has traditionally involved psychosocial and psychotherapeutic interventions. Pharmacotherapy, however, in conjunction with behavioral therapy, is generating interest as another modality to prevent relapse and enhance abstinence. Naltrexone and acamprosate are at the forefront of the currently available pharmacological options. Naltrexone is an opioid receptor antagonist and is thought to reduce the rewarding effect of alcohol. Acamprosate normalizes the dysregulation of N-methyl-D-aspartate (NMDA)-mediated glutamatergic excitation that occurs in alcohol withdrawal and early abstinence.These different mechanisms of action and different target neurotransmitter systems may endow the two drugs with efficacy for different aspects of alcohol use behavior. Since not all patients seem to benefit from naltrexone and acamprosate, there are ongoing efforts to improve the treatment outcomes by examining the advantages of combined pharmacotherapy and exploring the variables that might predict the response of the medications. In addition, novel medications are being investigated to assess their efficacy in preventing relapse and increasing abstinence.
gamma-Aminobutyric Acid/metabolism ; Taurine/analogs & derivatives/therapeutic use ; Recurrence ; Receptors, Opioid, mu/genetics/metabolism ; Receptors, Opioid/antagonists & inhibitors ; Polymorphism, Genetic ; Neurons/metabolism ; Naltrexone/therapeutic use ; N-Methylaspartate/metabolism ; Models, Neurological ; Models, Biological ; Humans ; Glutamine/metabolism ; Disulfiram/therapeutic use ; Alcoholism/*drug therapy ; Alcohol Deterrents/*therapeutic use