Effects of cocaine and fear

CLARITY – the technique that gave us the transparent mouse – have used the technique to show the effects of cocaine and fear on the brain.

The technique uses acrylamide to create a matrix in the cells and preserve their structure along with the DNA and proteins inside them, while the opaque lipids in the organs are dissolved to leave perfectly transparent cells.

Now it’s been put to use to show how the brain reacts to stimuli. As Nature reports:

…neuroscientists Li Ye and Karl Deisseroth of Stanford University in California engineered mice so that their neurons would make a fluorescent protein when they fired. (The system is activated by the injection of a drug.) The researchers then trained four of these mice to expect a painful foot shock when placed in a particular box; another set of mice placed in the box received cocaine, rather than shocks.

Once the mice had learned to associate the box with either pain or an addictive reward, the researchers tested how the animals’ brains responded to the stimuli. They injected the mice with the drug that activated the fluorescent protein system, placed them in the box and waited for one hour to give their neurons time to fire.

They were then killed, their brains removed and treated with CLARITY. The resulting images were combined by computer which, as seen in the video above, shows the pathways that lit up when mice were either afraid or expecting cocaine.

Deisseroth says that experiment highlights the complex “connections and cross-talk between different parts of the brain” that occur in behaviours such as addiction.