Pain
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Persons with Alzheimer disease (AD) commonly present with chronic nonmalignant pain, but long-term use of opioids among this population has not been studied previously. Our aim was to investigate the prevalence of long-term (≥180 days) use of opioids for nonmalignant pain and associated factors among community-dwelling persons with AD and to compare the prevalence with a matched cohort without AD. The Medication use and Alzheimer's disease (MEDALZ) cohort was used for this study, comprising all community-dwelling persons diagnosed with AD in Finland during 2005 to 2011 and their matched comparison persons without AD. ⋯ Factors associated with long-term opioid use included AD, age ≥80 years, female sex, rheumatoid arthritis, osteoporosis, low socioeconomic position, history of substance abuse, and long-term benzodiazepine use. Prevalence of long-term opioid use was somewhat similar among both groups. Among persons with AD, long-term opioid use was strongly associated with transdermal opioids.
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The processing of reward and reinforcement learning seems to be important determinants of pain chronicity. However, reward processing is already altered early in life and if this is related to the development of pain symptoms later on is not known. The aim of this study was first to examine whether behavioural and brain-related indicators of reward processing at the age of 14 to 15 years are significant predictors of pain complaints 2 years later, at 16 to 17 years. ⋯ The relationship of pain complaints and activation in the periaqueductal gray and ventral striatum depended on the T-allele of rs563649. Carriers of this allele also showed more pain complaints than CC-allele carriers. Therefore, brain responses to reward outcomes and higher sensitivity to pain might be related already early in life and may thus set the course for pain complaints later in life, partly depending on a specific opioidergic genetic predisposition.
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Virus-mediated gene delivery shows promise for the treatment of chronic pain. However, viral vectors have cytotoxicity. To avoid toxicities and limitations of virus-mediated gene delivery, we developed a novel nonviral hybrid vector: HIV-1 Tat peptide sequence modified with histidine and cysteine residues combined with a cationic lipid. ⋯ The effect was reversible with local naloxone administration. We quantified β-endorphin secretion from HSC-3 cells and showed that HSC-3 cells transfected with OPRM1 secreted significantly more β-endorphin than control HSC-3 cells. These findings indicate that nonviral delivery of the OPRM1 gene targeted to the cancer microenvironment has an analgesic effect in a preclinical cancer model, and nonviral gene delivery is a potential treatment for cancer pain.