The faulty mechanism is a failure to clear away a substance known as gamma-Aminobutyric acid (GABA) that inhibits signaling around neurons, or brain cells, in the central amygdala.
he amygdala is a region of the brain concerned with emotion, learning, memory, and motivation.
The scientists report their findings in a paper now published in the journal Science.
“We have to understand,” explains senior study author Markus Heilig, who is a professor in clinical and experimental medicine at Linköping University in Sweden, “that a core feature of addiction is that you know it is going to harm you, potentially even kill you, and nevertheless something has gone wrong with the motivational control and you keep doing it.”
When the researchers looked inside the rats’ brains, they discovered what might be disrupting the “motivational control.” First, they looked for differences in gene expression in different parts of the brain. The biggest differences were in the amygdala.
They revealed that the gene that codes for a protein called GAT-3 was expressed at much lower levels in the amygdala of the rats that continued to choose alcohol compared with the rats that switched to sugared water.
GAT-3 is a “transporter” protein that helps to clear away GABA from around neurons. Studies have also revealed that rats that become addicted to alcohol seem to have altered GABA signaling.
A molecular mechanism for choosing alcohol over an alternative reward