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The Effects of Cocaine on Blood Flow in the Brain

A new imaging technique captured the flow of blood in the brain of a mouse chronically exposed to cocaine.
Image: Shutterstock

Forget smashed eggs, this is actually a brain on drugs—a mouse brain on cocaine, to be precise. Researchers developed a new imaging technique to capture the flow of blood in the brain, and one use it could have is to better understand the effects of drug abuse.

Image: from the paper in Biomedical Optics Express

The image on the left shows the brain of a drug-free mouse, and the one on the right shows the brain of a mouse chronically exposed to cocaine. You'll notice the latter is quite clearly darker, which means there's less blood flow there.

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In their study published in the journal Biomedical Optics Express, the researchers from Stony Brook University in New York and the US National Institutes of Health write that their experiments on live mice show "drastic vasoconstriction and microischemia [a restriction to blood supply] elicited by chronic cocaine administration or by repeated acute cocaine challenges." In the second image, the dashed outlines highlight examples of vasoconstriction—when blood vessels narrow, reducing the blood flow through them.

That's not a new finding; it's well-known that cocaine causes vasoconstriction. But this is the first time that the effects on blood flow have been documented, thanks to the imaging method the researchers used. They explained that existing techniques like two-photon microscopy and fMRI scans lacked the field of view or resolution, respectively, to capture both the bigger picture and the blood flow in individual vessels.

They used a relatively new method called optical coherence Doppler tomography. Essentially, this directs a laser at the cells that bounces back. As the blood cells are moving, the frequency of the light wave shifts slightly. A statement on the Optical Society's website (the society behind the journal), explains that it's like the Doppler effect you get when a siren moves past you and appears to change pitch. Working off of that, the researchers can tell the speed of the blood flow.

Led by biomedical engineer Yingtian Pan, the team tweaked the imaging method using an image processing technique they developed so they could capture a wider range of blood flow speeds. It still has its limitations, however: For one, it can only image down to a millimetre or so below the surface, which might be ok for mice but wouldn't give you much detail on a human brain. In the statement, Pan suggested it could perhaps be used during open brain surgery, when you can get in close to areas of interest.

The researchers concluded, "Neuroimaging techniques that enable high spatiotemporal resolution and quantitative imaging of the cerebral blood flow network and dynamics are of high clinical relevance and may provide important insight into brain physiology." These early findings might offer an initial suggestion of the kind of techniques that could help us get just that little bit closer to unravelling the enduring mysteries of the brain.