Neuraxial opioids, widely used in obstetric and perioperative pain management, often lead to unwanted itch, reducing patient satisfaction. While the μ-opioid receptor has been implicated in opioid-induced itch, the genetic basis for variable itch incidence remains unknown. This study examined 3616 patients receiving epidural opioids, revealing an itch occurrence of 26.55%, with variations among opioid types and gender. Analysis of the OPRM1 gene identified six single-nucleotide polymorphisms, notably rs1799971 (A118G), that correlated with opioid-induced itch. Mouse models with an equivalent A112G mutation showed reduced neuraxial opioid-induced itch and light touch-evoked itch, mirroring human findings. The 118G allele demonstrated an anti-itch effect without impacting analgesia, addiction, or tolerance, offering insights for risk stratification and potential anti-itch pretreatment strategies.
Receptors, Opioid, mu/genetics* ; Pruritus/chemically induced* ; Humans ; Analgesics, Opioid/administration & dosage* ; Female ; Male ; Animals ; Polymorphism, Single Nucleotide/genetics* ; Adult ; Mice ; Middle Aged

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 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

Association between postoperative nausea and vomiting (PONV) and micro-opioid receptor A118G single nucleotide polymorphism (SNP) is undefined and might underlie inconsistent results of studies on PONV occurrence in patients undergoing general anesthesia with the opioid, remifentanil. Four hundred and sixteen Korean women undergoing breast surgery with general anesthesia were randomized to receive remifentanil 10 ng/mL (plasma-site, Minto model) using a target-controlled infusion device and either propofol for total intravenous anesthesia (T group) or sevoflurane for inhalation anesthesia (I group) with bispectral index values maintained between 40 and 60. Blood specimens were collected after anesthesia induction for A118G SNP analysis. PONV and postoperative pain were evaluated. A118G SNP type distribution among Korean female adults studied was AG (n=195)>AA (n=158)>GG (n=63). Regardless of anesthetic technique, patients with GG types had lower PONV scale on arrival at postoperative care unit (PACU) (P=0.002), while T group showed lower PONV scale than I group up to 6 hr after PACU discharge in AA and AG types. No differences were apparent for postoperative pain among opioid receptor polymorphism. PONV occurrence differs according to opioid receptor polymorphism and anesthetic technique in patients undergoing general anesthesia with remifentanil.
Adult ; Analgesics, Opioid/*adverse effects ; Anesthesia, General/*adverse effects ; Breast Diseases/surgery ; Demography ; Double-Blind Method ; Female ; Humans ; Methyl Ethers/adverse effects/therapeutic use ; Pain, Postoperative/drug therapy ; Piperidines/*adverse effects/therapeutic use ; *Polymorphism, Single Nucleotide ; Postoperative Nausea and Vomiting/*etiology ; Receptors, Opioid, mu/*genetics

Pain perception is influenced by multiple factors. The single nucleotide polymorphisms (SNPs) of some genes were found associated with pain perception. This study aimed to examine the association of the genotypes of ABCB1 C3435T, OPRM1 A118G and COMT V108/158M (valine 108/158 methionine) with pain perception in cancer patients. We genotyped 146 cancer pain patients and 139 cancer patients without pain for ABCB1 C3435T (rs1045642), OPRM1 A118G (rs1799971) and COMT V108/158M (rs4680) by the fluorescent dye-terminator cycle sequencing method, and compared the genotype distribution between groups with different pain intensities by chi-square test and pain scores between groups with different genotypes by non-parametric test. The results showed that in these cancer patients, the frequency of variant T allele of ABCB1 C3435T was 40.5%; that of G allele of OPRM1 A118G was 38.5% and that of A allele of COMT V108/158M was 23.3%. No significant difference in the genotype distribution of ABCB1 C3435T (rs1045642) and OPRM1 A118G (rs1799971) was observed between cancer pain group and control group (P=0.364 and 0.578); however, significant difference occurred in the genotype distribution of COMT V108/158M (rs4680) between the two groups (P=0.001). And the difference could not be explained by any other confounding factors. Moreover, we found that the genotypes of COMT V108/158M and ABCB1 C3435T were associated with the intensities of pain in cancer patients. In conclusion, our results indicate that the SNPs of COMT V108/158M and ABCB1 C3435T significantly influence the pain perception in Chinese cancer patients.
ATP Binding Cassette Transporter, Sub-Family B ; genetics ; Adult ; Aged ; Aged, 80 and over ; Alleles ; Breast Neoplasms ; complications ; diagnosis ; genetics ; pathology ; Catechol O-Methyltransferase ; genetics ; Female ; Gastrointestinal Neoplasms ; complications ; diagnosis ; genetics ; pathology ; Gene Expression ; Gene Frequency ; Genital Neoplasms, Female ; complications ; diagnosis ; genetics ; pathology ; Genital Neoplasms, Male ; complications ; diagnosis ; genetics ; pathology ; Genotype ; Humans ; Lung Neoplasms ; complications ; diagnosis ; genetics ; pathology ; Male ; Middle Aged ; Pain ; complications ; diagnosis ; genetics ; pathology ; Pain Measurement ; Pain Perception ; Polymorphism, Single Nucleotide ; Receptors, Opioid, mu ; genetics

Substantial evidence has suggested that deep brain stimulation of the cuneiform nucleus has become a remarkable treatment option for intractable pain, but the possible mechanism is poorly understood. Using a melanocortin-4 receptor (MC4R)-green fluorescent protein (GFP) reporter knockin mouse, we showed that a large number of MC4R-GFP-positive neurons were expressed in the cuneiform nucleus. Immunofluorescence revealed that approximately 40%-50% of MC4R-GFP-positive neurons expressed mu opioid receptors, indicating that they were opioidergic signaling. Our findings support the hypothesis that MC4R expression in the cuneiform nucleus is involved in the modulation of opioidergic signaling.
Animals ; Gene Expression Regulation ; Gene Knock-In Techniques ; Genes, Reporter ; Green Fluorescent Proteins ; genetics ; metabolism ; Mice ; Mice, Transgenic ; Microtomy ; Midbrain Reticular Formation ; cytology ; metabolism ; Neurons ; cytology ; metabolism ; Receptor, Melanocortin, Type 4 ; genetics ; metabolism ; Receptors, Opioid, mu ; genetics ; metabolism ; Recombinant Fusion Proteins ; genetics ; metabolism ; Signal Transduction

Non-steroidal anti-inflammatory drugs (NSAIDs) induce tissue damage and oxidative stress in animal models of stomach damage. In the present study, the protective effects of wheat peptides were evaluated in a NSAID-induced stomach damage model in rats. Different doses of wheat peptides or distilled water were administered daily by gavage for 30 days before the rat stomach damage model was established by administration of NSAIDs (aspirin and indomethacin) into the digestive tract twice. The treatment of wheat peptides decreased the NSAID-induced gastric epithelial cell degeneration and oxidative stress and NO levels in the rats. Wheat peptides significantly increased the superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and decreased iNOS activity in stomach. The mRNA expression level of μ-opioid receptor was significantly decreased in wheat peptides-treated rats than that in in the control rats. The results suggest that NSAID drugs induced stomach damage in rats, wchih can be prevented by wheat peptides. The mechanisms for the protective effects were most likely through reducing NSAID-induced oxidative stress.
Animals ; Anti-Inflammatory Agents, Non-Steroidal ; adverse effects ; Antioxidants ; pharmacology ; Aspirin ; adverse effects ; Gastric Mucosa ; drug effects ; Gene Expression ; Glutathione Peroxidase ; drug effects ; Indomethacin ; adverse effects ; Male ; Nitric Oxide ; biosynthesis ; Nitric Oxide Synthase ; chemical synthesis ; Oxidation-Reduction ; Oxidative Stress ; drug effects ; Plant Proteins ; pharmacology ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; drug effects ; Stomach ; drug effects ; Superoxide Dismutase ; drug effects ; Triticum ; chemistry

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

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

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