The neurotransmitter in question is dopamine.
The receptor deficiency is D2 (one of the types of dopamine receptor) .
The specific brain area is the ventral (front) area of the striatum, the nucleus accumbens.
Details of the study: "Researchers at the University of Cambridge in England report in this week's Science that a lower number of specific types of receptors that bind the neurotransmitter dopamine—a chemical central to the brain's reward system—in the front (or ventral) section of the striatum (a midbrain region implicated in planning and movement as well as executive function) correlates to increased impulsive behavior in rats. In addition, they found that the more impulsive animals, when given the option, consumed more cocaine than the calmer rats did. "
This just means that some brains are more susceptible to drug addiction, and they hypothesize that deficiencies in the D2 receptor in the nucleus accumbens of the brain may explain why.
Clinical Implications (aka how I'll use it with my patients):
Many chemically dependent patients have a lot of guilt and poor self esteem around their drug abuse. This is not necessarily a bad thing, but when they start expanding this into judgements about their moral character, and being a 'bad' person, it can get in the way of treatment. By explaining to them that their addictive nature may be at least partially due to brain chemistry, it often helps them to separate out addiction from morality. I don't mean to imply that someone is not responsible for their actions. Rather, it's that if someone knows their brain has a vulnerability (ie. addiction), then they need to change their environment and/or behavior(s) if they want to stay out of trouble.
A less charged example: if you are diabetic, your body just can't process carbohydrates and sugars as well as the average person. It doesn't make you a bad person because your body is different. However, if you don't make accommodations (ie. change your diet, take medications or insulin, make efforts to keep you blood glucose in balance), you will get sick, your organs will fail, and it will likely kill you.
Basically, this supports the disease model for addiction and mental illness, rather than a character judgement about the 'weakness' of an individual. Doesn't mean they can use this as an excuse to abuse drugs either, unless they want to give up on the idea of free will.
Happy Friday everyone!