Addiction: Symptom of Inherited Brain Deficits

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“It’s the first time scientists have shown in selectively bred animals that the propensity for addiction is linked to differences in expression of genes for specific molecules in a specific brain region. It’s also the first demonstration that a DNA tag called an epigenetic marker can predispose an individual to addiction and relapse.

The researchers looked in rats’ brains for the genetic instructions needed to make a key “pleasure receptor,” called D2, that allows brain cells to receive signals sent by the brain chemical dopamine — or cocaine. They found that more addiction-prone rats had lower levels of D2 instructions to begin with, compared with other rats, in an area of the brain known to play a major role in addiction.

The addiction-prone rats also were more likely to carry a specific mark on their DNA called an epigenetic tag. This tag, called H3K9me3, kept their brain cells from reading the gene for D2 receptors.

But after they became hooked on cocaine, the addiction-prone rats had the same levels of D2 as the less addiction-prone ones.”

“Smaller amygdala and medial prefrontal cortex predict escalating stimulant use,” published online on May 13 in Brain: A Journal of Neurology has found that individual differences in brain structure could help to determine the risk for future drug addiction. The study found that occasional users who subsequently increased their drug use compared with those who did not, showed brain structural differences when they started using drugs…

individual differences in fronto-stiato-limbic regions implicated in impulsivity and decision making could render individuals vulnerable for the transition from occasional to escalating stimulant use.”

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