Single Nucleotide Polymorphisms Associated with Pain Sensitivity After Laparoscopic Cholecystectomy.

Objective: To systematically evaluate variations in single-nucleotide polymorphisms within 13 candidate pain genes in patients differing in phenotype characteristics based on a composite measure of pain sensitivity. Methods: In a case-control study, 149 patients scheduled for laparoscopic cholecystectomy were individually categorized according to preoperative pain sensitivity and postoperative pain intensity. Cases (pain group) reported cannulation-induced pain intensity higher than 2.0, together with postoperative pain intensity of 7.0 or higher (visual analog scale [VAS] units), and controls (low-pain group) reported cannulation-induced pain intensity of 2.0 or lower, together with postoperative pain intensity lower than 4.0 (VAS units). Genotyping of exomes was performed in 32 case and 25 control patients compared with respect to variations within 13 candidate pain genes. Results: There were no statistically significant differences in single nucleotide polymorphisms (SNPs) within the candidate genes between the case and control groups, but minor allele SNPs in the ABCB1 and COMT genes were more common in patients with higher levels of pain sensitivity and intensity. Conclusion: In this candidate gene study, based on a composite measure of pain sensitivity, no variations reached statistical significance after correction for multiple testing, most likely due to the large number of markers analyzed and few patients. Nevertheless, the results suggest a possible genetic contribution of single-nucleotide polymorphisms within the ABCB1 and COMT genes in individuals with higher levels of pain sensitivity.

Depressed mood, anxiety, and the use of labor analgesia.

Relatively little is known about mental health and labor pain. The aim of this study was to assess if self-rated antenatal depressed mood and anxiety are associated with pain-related behaviors and self-reported labor pain. We also wanted to replicate our previous finding of altered labor pain behavior in carriers of a specific guanosine triphosphate cyclohydrolase 1 gene (GCH1) haplotype. Ninety-nine women in gestational weeks 37 to 40 filled out questionnaires on depression and anxiety symptoms and later rated their labor pain by use of visual analog scales. Each subject was also genotyped for GCH1. Following adjustment for relevant confounders, women who arrived early to the delivery unit (cervical dilation <5 cm) had a significantly higher antenatal Montgomery-Åsberg Depression Rating Scale (MADRS-S) score, p < 0.05, than late arrivers (cervical dilation >5 cm). Women with increased Spielberger State-Trait Anxiety Inventory (STAI-T) scores reported higher self-rated pain prior to labor analgesia, p < 0.05, than women with low STAI-T scores. No association between the GCH1 pain-protective haplotype and cervical dilation was found, but a previously demonstrated association with increased use of second-line analgesia was confirmed. Depressed mood during pregnancy is associated with early arrival to the delivery department, whereas antenatal anxiety is associated with increased self-rated pain prior to labor analgesia.

The A118G single-nucleotide polymorphism of human µ-opioid receptor gene and use of labor analgesia.

The human µ-opioid receptor (MOR) is the major site of action of endogenous opioids and most of the clinically used opioid analgesics. The single-nucleotide polymorphism (SNP), A118G of the MOR 1 gene (OPRM1), has been associated with altered pain perception. The aim of this study was to investigate whether this polymorphism of OPRM1 is associated with a number of pain-related behaviors during labor. In this observational retrospective population-based study, pregnant women (n = 814) were recruited at gestational week 18. A plasma sample was collected from each participant and an SNP genotyping assay was performed. No differences in sociodemographic variables or labor pain-related outcomes, such as stage of cervical dilation on arrival at the delivery unit or use of any type of second-line analgesia during spontaneous labor, were found between noncarriers and G-allele carriers of OPRM1. We conclude that there is no association between the A118G polymorphism of OPRM1 regarding pain-related behavior during labor.