ORLANDO — Two neurologic systems reinforce alcohol dependence—both dopamine and serotonin pathways—and make it more difficult for people to stop drinking, according to a presentation at a psychopharmacology congress sponsored by the Neuroscience Education Institute.
“The neurobiology has led us where there are spectacular new targets for treatment of alcoholism,” said George F. Koob, Ph.D., professor and chairman of the committee on the neurobiology of addictive disorders at the Scripps Research Institute, La Jolla, Calif.
Rewarding effects of alcohol may be mediated by dopaminergic and opioidergic systems, Dr. Koob said. The pleasure provided through the mesolimbic pathway explains why people initially drink alcohol or take drugs. Dopamine is released in the front end of the brain while opioids activate the ventral tegmental area and nucleus accumbens. Impulsive drinking, particularly in young males, is an activation of reward mechanisms driven by initial pleasurable effects, Dr. Koob said. “As a person continues to drink, the reward system gets impaired but hyperarousal in the brain is set up that only alcohol will suppress. So [drinking] becomes self-medicating. …Those people you knew in college who could drink everyone under the table ultimately end up with a problem.”
The acute double action of alcohol is to enhance γ-aminobutyric acid (GABA) and decrease glutamate, Dr. Koob said. Both dopamine and serotonin pathways may mediate alcohol dependence. The frontal cortex, amygdala, and hippocampus are brain areas that might contribute to dependence, he added.
Consumption of alcohol also may alter regulatory agents of stress, particularly increasing corticotropin releasing factor (CRF) activity and decreasing neuropeptide Y. “While you are bingeing on alcohol, you are releasing the good guys like dopamine peptides, but when you get into withdrawal, you are recruiting the bad guys—the GABA system and the CRF stress hormone,” Dr. Koob said.
“You have a double-whammy effect when you become dependent—you lose the good guys and gain the brain stress system—so you continue to self-medicate with your drug of choice.”