Background: Opioids are associated with wide inter-individual variability in the analgesic response and a narrow therapeutic index. This may be partly explained by the presence of single nucleotide polymorphisms (SNPs) in genes encoding molecular entities involved in opioid metabolism and receptor activation. This paper describes the investigation of SNPs in three genes that have a functional impact on the opioid response: OPRM1, which codes for the μ-opioid receptor; ABCB1 for the ATP-binding cassette B1 transporter enzyme; and the calcium channel complex subunit CACNA2D2. The genotyping was combined with an analysis of plasma levels of the opioid peptide β-endorphin in 80 well-defined patients with chronic low back pain scheduled for spinal fusion surgery, and with differential sensitivity to the opioid analgesic remifentanil. This patient group was compared with 56 healthy controls.Results: The plasma β-endorphin levels were significantly higher in controls than in pain patients.A higher incidence of opioid-related side effects and sex differences was found in patients with the minor allele of the ABCB1 gene. Further, a correlation between increased opioid sensitivity and the major CACNA2D2 allele was confirmed. A tendency of a relationship between opioid sensitivity and the minor allele of OPRM1 was also found.Conclusions: Although the sample cohort in this study was limited to 80 patients it appears that it was possible to observe significant correlations between polymorphism in relevant genes and various items related to pain sensitivity and opioid response. Of particular interest is the new finding of a correlation between increased opioid sensitivity and the major CACNA2D2 allele. These observations may open for improved strategies in the clinical treatment of chronic pain with opioids.

The use of anabolic androgenic steroids (AASs) among non-athletes is a public health-problem, as abusers underestimate the negative effects associated with these drugs. The present study investigated the toxic effects of testosterone, nandrolone, stanozolol, and trenbolone, and aimed to understand how AAS abuse affects the brain. Mixed cortical cultures from embryonic rats were grown in vitro for 7 days and thereafter treated with increasing concentrations of AASs for 24 h (single-dose) or 3 days (repeated exposure). Cells were co-treated with the androgen-receptor (AR) antagonist flutamide, to determine whether the potential adverse effects observed were mediated by the AR. Cellular toxicity was determined by measuring mitochondrial activity, lactate dehydrogenase (LDH) release, and caspase-3/7 activity. Nandrolone, unlike the other AASs studied, indicated an effect on mitochondrial activity after 24 h. Furthermore, single-dose exposure with testosterone, nandrolone and trenbolone increased LDH release, while no effect was detected with stanozolol. However, all of the four steroids negatively affected mitochondrial function and resulted in LDH release after repeated exposure. Testosterone, nandrolone, and trenbolone caused their toxic effects by induction of apoptosis, unlike stanozolol that seemed to induce necrosis. Flutamide almost completely prevented AAS-induced toxicity by maintaining mitochondrial function, cellular integrity, and inhibition of apoptosis. Overall, we found that supra-physiological concentrations of AASs induce cell death in mixed primary cortical cultures, but to different extents, and possibly through various mechanisms. The data presented herein suggest that the molecular interactions of the AASs with the AR are primarily responsible for the toxic outcomes observed.