Drugs Of Abuse Target Brain’s Pleasure Center Pathways.

In Brain Circuitry, Brain General Structure and Function, Brain Science by Brainy Days Ahead

Drugs of abuse and the science behind addiction remain poorly understood. Researchers at University of Utah Health devised a system that allowed zebrafish, a small tropical fish, to self-administer doses of hydrocodone, an opioid commonly prescribed to people for pain. After one-week, the fish had increased their drug-seeking behavior, even when doing so required them to put themselves in risky conditions. Further, 48-hours after the last exposure, conditioned fish showed signs of anxiety, a hallmark of withdrawal. Zebrafish share 70 percent of genes with people and also share similar biological pathways that lead to addiction. Drug-seeking behavior also increased when the zebrafish were forced to receive the opioid in progressively shallower water, a stressful environmental setting that unconditioned fish would avoid. Further, fish that received a reduced dose of hydrocodone at the original depth increased their drug-seeking behavior to obtain an equivalent “fix.” Conditioned zebrafish treated with naloxone, a drug that blocks the m-opioid receptor, as well as dopamine- or glutamate-blockers reduced their drug-seeking behavior during the experiments. The researchers plan to use their zebrafish model to search for new therapeutics that could block drug-seeking behavior.