The stark reality of drug abuse hit home for Brendan Walker when two college classmates overdosed on heroin and Xanax. Their unsettling deaths steered Walker toward a career in the neuroscience of psychology and addictions.
Today, the associate professor of psychology and member of the Neuroscience Program at WSU is a leader in the study of alcohol and opioid drug dependence. His research is advancing the development of new pharmacotherapy treatments for addiction.
“Alcohol and abused opioids have a lot of similarity,” says Walker. “They both manipulate very powerful primitive systems in the brain that are critical for our motivation.”
One of those systems is the body’s natural opioid system which controls emotional and behavioral responses to stress and pain. Walker says the system produces both “good” and “bad” opioids that counter each other to maintain emotional balance.
The good opioids—endorphins—relieve pain and create euphoria while the bad opioids—dynorphins—cause anxiety and depression. Alcohol and heroin, for example, trigger pleasurable endorphin release but dynorphins are responsible for the agony that occurs during withdrawal. More alcohol or heroin eases that distress and the vicious cycle continues. It also results in unhealthy brain changes.
Those changes are the subject of Walker’s research, especially the brain receptors that bind dynorphins called kappa opioid receptors or KORs.
In a 2014 study, Walker showed that in alcohol dependent rats, the dynorphin system becomes overactive and unbalanced. The dysfunctional KORs now trigger excessive alcohol intake during withdrawal, further fueling the addiction. He says these findings apply to heroin and other opioid dependence as well.
Walker’s studies indicate that a new therapeutic drug called nalmefene “in part, blocks kappa opioid receptors and essentially returns the animal’s brain to a normal, non-dependent state—reducing the need to drink or use excessively,” he says.
Nalmefene was released in the European Union in 2013 for treatment of alcoholism. Walker, whose pre-clinical data contributed to that release, says the drug also holds potential for the treatment of opioid addiction.