How Cocaine Alters the Brain: Drug's Impact on Neural Function

How does cocaine change the human brain? Scientists have taken a closer look at this drug and the brains of users to better understand what goes on when the drug is taken.

In this latest study, the researchers used tracer molecules to follow electrical activity in the brain in rats exposed to cocaine. The scientists found that a hub of neurons in the extended amygdala, which is the brain's motivation/learning center, acts as a relay between activation of the ventrical subiculum, which is the brain's addiction center, and the hyperactive release of dopamine.

Over time, though, increasing activation of a key part of the extended amygdala produces a long-lasting increase in signal transmission onto neurons that produce dopamine. This causes the rats to become desensitized to the cocaine. Because the change happens within the amygdala, it may explain some of the long-term effects on behavior and motivation that occur after prolonged cocaine use.

"Unraveling the neuronal circuit and characterizing the synaptic mechanisms by which the ventral subiculum alters the excitability of dopamine neurons is a necessary first step in understanding the resulting behavioral changes induced by cocaine," said Fracois Georges, one of the researchers, in a news release. "We show that the ventral subiculum recruits the bed nucleus of the stria terminalis to drive a persistent hyperactivity of dopamine neurons and control cocaine-induced activity."

The researchers also found a single stimulation had the same impact on the brain and dopamine neurons as a massive injection of cocaine. These effects lasted up to five days, and also raise the possibility that dopamine-producing neurons can be changed so that they respond differently to stimuli.

The findings are published in the journal Cell Reports.

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