January 24, 2011

Technology Gives Scientists Peek Deep Into Brain

Microscope image of a blood vessel network Blood vessel networks within the hippocampus can be seen using the new technique.Nature Medicine

Researchers have been able to see changes deep within the brains of living animals at the cellular level. The advance could provide an important tool for understanding diseases and disorders of the brain, including substance abuse and addiction.

Researchers can't currently study tissues in deep brain structures of a living animal with conventional light methods because light can't penetrate them. To overcome this, a team of scientists at Stanford University led by Dr. Mark Schnitzer set out to develop a way to use microlenses that can be directly inserted into brain regions of interest. Their work was supported by NIH's National Institute on Drug Abuse (NIDA), National Cancer Institute (NCI) and National Institute of Neurological Disorders and Stroke (NINDS).

The researchers described their technique, called time-lapse fluorescence microendoscopy, in the early online edition of Nature Medicine on January 16, 2011. They surgically implanted permanent guide tubes with their tips just above the areas they wanted to look at. They focused on 2 brain regions, the hippocampus and striatum. After the mice recovered from surgery, miniature microlens probes could be repeatedly inserted into the guide tubes over time without any effect on the animals.

The researchers first showed that they could use the new method to track the growth and branching of individual nerve cells and blood vessels over a period of several weeks. The technique provides a level of detail not possible with previous methods.

The scientists next investigated a mouse model of glioma, a malignant brain tumor. They demonstrated that it was possible to track and monitor the growth of blood vessels in these tumors over several weeks.

This new technique could lead to insights into the development and progression of many brain disorders, including neurodegenerative disorders and those caused by trauma. It could also help in the study of substance abuse and addiction. Some researchers believe that a shift in activity within the striatum is at least partly responsible for the transition from voluntary drug-taking to addiction.

"The results should now allow neuroscientists to track longitudinally in the living brain the effects of drugs of abuse at the levels of neural circuitry, the individual neuron and neuronal dendrites," Schnitzer says.

"Continued drug use leads to changes in neuronal circuits that are evident well after a person stops taking an addictive substance," says Dr. Nora D. Volkow, director of NIDA. "This study introduces an innovative technique that allows for a glimpse of these cellular changes within the brain regions implicated in drug reward, providing an important tool in our understanding and treatment of addiction."

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