Hangover Helps Drinkers Limit Alcohol Intake

While many studies have focused on the reward system that alcohol and other recreational drugs trigger in the brain, neuroscientists at the University of Utah recently took a closer look at how the brain responds to the negative effects of alcohol.

Sensitivity to the aversive consequences that may follow a heavy drinking session—which might include alcohol-induced sedation, nausea, or hangover—are key to limiting alcohol intake. A region of the brain called the lateral habenula plays an important role in this aversion learning.
____________________________________________________________________________________________________________________________________________________________________

Related Content
How Safe Is Alcohol for Patients With Diabetes?
Anticonvulsant May Aid in Alcohol Dependence
____________________________________________________________________________________________________________________________________________________________________

To get a better understanding of how these aversive effects regulate alcohol intake, the researchers inactivated the lateral habenula in a group of rats. Then, they provided that group as well as a control group with intermittent access to a solution of 20% alcohol over several weeks.

The inactivated group escalated their drinking faster, drinking more alcohol than the control group. “Our results are interesting because they emphasize the importance of drug-induced aversive experiences in regulating alcohol intake and escalation of alcohol intake,” says study author Sharif Taha, PhD, professor of neurobiology and anatomy at the University of Utah.

“Our main results show that chronic inactivation of the lateral habenula in rodents has two important behavioral consequences: 1) it increases the rate at which escalation of voluntary alcohol drinking occurs over weeks, resulting in higher daily levels of intake,” he says. “And 2) it reduces rats’ ability to learn from the aversive effects of alcohol.”

In a second part of the experiment, Taha and his colleagues tested whether the inactivated lateral habenula rats were failing to learn from negative experiences associated with the alcohol.

They gave the rats a sweet-tasting juice, but then injected them with enough alcohol to cause negative effects. While the control group learned their lesson and stayed away from the juice, the inactivated lateral habenula rats continued to go back for more despite their bad experience.

“Our evidence suggests that alcohol’s effects on the lateral habenula may be an important mediator of these aversive effects and/or learning from these aversive effects in rodent models,” Taha says. “So now it will be interesting and important to see if the lateral habenula plays a similar role in humans. Ultimately, these studies could be important in understanding the brain mechanisms that control vulnerability to alcoholism.”

The researchers say their most important steps going forward will be:

• to characterize alcohol’s effects on the firing of neurons in the lateral habenula, so they can begin to understand how alcohol changes signaling in these neurons; and

• to determine if changes in alcohol-induced aversion learning are causally responsible for the rapid escalation of alcohol intake observed in the rodents with an inactivated lateral habenula.

“Our recently published study showed that lateral habenula inactivation increased drinking and decreased alcohol-induced aversion learning,” Taha says. “It’s important now to see if the latter causes the former, as we hypothesize.”

 —Colleen Mullarkey

Reference

Haack AK, Sheth C, Schwager AL, Sinclair MS, Tandon S, Taha SA. Lesions of the lateral habenula increase voluntary ethanol consumption and operant self-administration, block yohimbine-induced reinstatement of ethanol seeking, and attenuate ethanol-induced conditioned taste aversion. PLOS One. Apr 2, 2014. [Epub ahead of print]. DOI: 10.1371/journal.pone.0092701