Stressed Out Rats Drink More Alcohol. Sound Familiar?

We've all been there: after a particularly long and stressful day, nothing sounds better than heading to the nearest watering hole for a drink. There's a reason for this—stress and alcohol target similar neural systems, particularly the brain's reward center. The problem is chronic stress, rather than just the occasional bad day, actually alters the brain's reward circuitry, creating a feedback loop that leads to increasing alcohol consumption.

The link between chronic stress and alcohol abuse is pretty well established, but the underlying brain chemistry responsible for this connection is not well understood. To tackle this problem, a team of neuroscientists at the University of Pennsylvania exposed rats to an acute stress and then allowed the rodents to self-administer alcohol after being stressed while the team monitored the rats' neuronal activity.

As the team detailed in a paper published in Neuron, the rats were exposed to a restraint stress (in which a rat is basically put inside a tube only slightly larger than its body) for one hour, and then 15 hours later the researchers measured how much sugar water laced with alcohol the rats consumed.

What they found was that the stressed out rats drank significantly more alcohol than non-stressed rats and increased their alcohol intake over the course of several weeks.

When you drink alcohol, it works on a number of neurotransmitters in the brain such as GABA which is responsible for the sedative effects of alcohol. But of particular interest here is the dopamine surge induced by alcohol in the ventral tegmental, ground zero of the brain's reward center. The reason that the rats who had been exposed to stress were drinking more than their non-stressed counterparts is that the stress had altered the neuron physiology of the rats' brains in the reward center, according to the UPenn researchers.

Specifically, the GABA neurotransmitters that are normally inhibitory flipped to become excitatory, which blunted the brain's response to alcohol-induced dopamine release.

Although GABA is typically an inhibitory neurotransmitter, the UPenn study and prior research has shown that it can become excitatory under certain stressful conditions, such as epilepsy or neuronal trauma.

In other words, the stress induced rats to drink more alcohol, but the stress also rendered the higher levels of alcohol intake less effective because it resulted in an increased GABA response which blunts the effects of dopamine release.

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