Why Do Certain People Get Hooked on Painkillers?
A missing enzyme in the brain could put some people at higher risk for opioid addiction.
A missing brain enzyme could be responsible for painkiller addiction, according to a new study. With prescription drug abuse reaching epidemic levels, researchers at the University of Medicine and Science in Los Angeles examined why some people are more vulnerable to opioid addiction than others. Opioids are produced naturally in the body, but addiction occurs when synthetic opioids—found in heroin and prescription medications like morphine and codeine—alter brain chemical balance. The researchers used mice and eliminated an enzyme called prohormone convertase 2 (PC2)—which converts pre-hormonal substances into active hormones in certain parts of the brain. Past research by the same team found that PC2 levels increase after long-term morphine treatment. “This raises the possibility that PC2-derived peptides may be involved in some of the addiction parameters related to morphine," says Theodore C. Friedman, MD, PhD, chairman of the internal medicine department at Charles R. Drew University of Medicine and Science in Los Angeles. After knocking out the PC2 enzyme in mice, Friedman and his team analyzed the effects of morphine on the brain. Their results show that concentrations of MOR—the mu opioid receptor that morphine normally binds to—were higher in mice lacking PC2. "In this study, we found that PC2 knockout mice have higher levels of MOR in brain regions related to drug addiction," Friedman says. "We conclude that PC2 regulates endogenous opioids involved in the addiction response and in its absence, up-regulation of MOR expression occurs in key brain areas related to drug addiction." The researchers see these results as promising, and are expected to conduct more studies of this nature in the near future.