Cocaine has always seemed like the absolute most pointless drug to me for the simple reason that its primary effect seems to be making the user want more cocaine. That’s an anecdotal statement, of course, but compared to any other common recreational drug, it really seems to the case: more, more. And then suddenly it's two mornings later, that more having won out, and you’re out of money and trying to stay awake at work. Good times—or something.
A new study out in Nature Neuroscience might give some insight into this particular phenomenon: researchers using 2-photon laser scanning microscopy to scan the frontal lobes of mice have found that after a single dose of cocaine, the brain forms new dendritic spines. These are the tiny structures that connect neurons and form nodes in the brain’s circuit wiring, increasing the number of contacts that neurons have to other neurons and also forming the physical substrate within which memories are stored. The spines and formation of new spines are critical in the brain’s ability to learn.
"Our images provide clear evidence that cocaine induces rapid gains in new spines, and the more spines the mice gain, the more they show they learned about the drug," says UC Berkley’s Linda Wilbrecht, the paper’s lead author. In other words, after a hit of cocaine the brain basically drops everything and builds a new space in said grey sponge for “cocaine.”
"The downside is, you might be learning too well about drugs at the expense of other things," she adds.
via UC Berkley. "Time-lapse images show wiring changes in the brain cells of a live mouse over multiple days after a cocaine. Green arrows indicate the growth of new spines, blue arrows show the loss of spines and yellow arrows show stable spines."
The really interesting thing is that the brain doesn’t just hardwire the feeling of cocaine, but a whole bunch of stuff that occurs around the cocaine experience. The researchers demonstrated this by using cocaine to rewire a mouse’s sober or “natural” preference between two tiny rooms with different decorations and different smells.
"When given a choice, most of the mice preferred to explore the side where they had the cocaine, which indicated that they were looking for more cocaine," Wilbrecht says. "Their change in preference for the cocaine side correlated with gains in new persistent spines that appeared on the day they experienced cocaine."
The paper’s suggestion from this is interesting: in human users, this rewiring might leave users with less ability to be stimulated by mundane, day-to-day things. "These drug-induced changes in the brain may explain how drug related cues come to dominate decision-making in a human drug user, leaving more mundane tasks and cues with relatively less power to activate the brain's decision-making centers," she explains. Cocaine makes the sober world boring, in other words.
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