Wednesday, October 30, 2013

Why Alcohol Is Addicting? (Part I)

Drinking alcohol leads to the release of endorphins in areas of the brain that produce feelings of pleasure and reward, according to a study led by researchers at the Ernest Gallo Clinic and Research Center at the University of California, San Francisco (UCSF).

Endorphins are small proteins with opiate-like effects
that are produced naturally in the brain.

The researchers used positron emission tomography, or

PET imaging,

to observe the immediate effects of alcohol in the brains of 13 heavy drinkers and 12 matched "control" subjects who were not heavy drinkers.

In all of the subjects, alcohol intake led to a release of endorphins. And, in all of the subjects, the more endorphins released in the nucleus accumbens,

the nucleus accumbens

the greater the feelings of pleasure reported by each drinker.

orbitofrontal cortex

In addition, the more endorphins released in the orbitofrontal cortex, the greater the feelings of intoxication in the heavy drinkers, but not in the control subjects.

Orbitofrontal  cortex (OFC) green area on diagram

The human OFC is involved in sensory integration, in representing the affective value of reinforcers, in  decision-making and expectation.

In particular, the OFC is important in signaling the expected rewards/punishments of an action given the particular details of a situation.

In doing this, the brain is capable of comparing the expected reward/punishment with the actual delivery of reward/punishment.

To be continued…

Natalia Levis-Fox

Journal Reference
J. M. Mitchell, J. P. O'Neil, M. Janabi, S. M. Marks, W. J. Jagust, H. L. Fields. Alcohol Consumption Induces Endogenous Opioid Release in the Human Orbitofrontal Cortex and Nucleus Accumbens. Science Translational Medicine, 2012; 4 (116): 116ra6 DOI: 10.1126/scitranslmed.3002902

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