The findings suggest a way in which drug use may lead to drug-seeking behaviour that fosters continued drug use, scientists said.
The researchers used a microscope that allowed them to peer directly into nerve cells within the brains of live mice, and within two hours of giving a drug they found significant increases in the density of dendritic spines - structures that bear synapses required for signaling - in the animals' frontal cortex.
In contrast, mice given saline solution showed no such increase, researchers said. The researchers also found a relationship between the growth of new dendritic spines and drug-associated learning.
Specifically, mice that grew the most new spines were those that developed the strongest preference for being in the enclosure where they received cocaine rather than in the enclosure where they received saline.
"This gives us a possible mechanism for how drug use fuels further drug-seeking behaviour," said principal investigator Linda Wilbrecht.
"It's been observed that long-term drug users show decreased function in the frontal cortex in connection with mundane cues or tasks, and increased function in response to drug-related activity or information," Wilbrecht said.
"This research suggests how the brain of drug users might shift towards those drug-related associations," she said.
In all living brains there is a baseline level of creation of new spines in response to, or in anticipation of, day-to-day learning, Wilbrecht said.
By enhancing this growth, cocaine might be a super-learning stimulus that reinforces learning about the cocaine experience, she said.
The frontal cortex, which Wilbrecht described the ‘steering wheel’ of the brain, controls functions such as long-term planning, decision-making and other behaviours involving higher reasoning and discipline.
The brain cells in the frontal cortex studied regulate the output of this brain region, and may play a key role in decision-making.
"These neurons, which are directly affected by cocaine use, have the potential to bias decision-making," Wilbrecht said.  


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