A CHEMICAL produced during sex and l inked to addiction has been visualised in a scanner as it washes across rats' brains. The feat means that functional magnetic resonance imaging (fMRI), a workhorse of neuroscience, can now be used to observe the flow of brain chemicals, not just oxygen - rich blood. By pin pointing increases in blood oxygenation in the brain in response to different events - a sign that specific groups of neurons are active - fMRI is responsible for some of the hottest findings about the brain . Now Alan jasan off at the Massachusetts Institute of Technology and colleagues have extended its power.
His team repeatedly mutated a magnetic, iron-containing enzyme that "lights up" i n fMRI readings. With each mutation, the researchers tested its tendency to bind to dopamine, a learning and reward chemical in the brain involved in sex and addictive behaviors. Mutations that increased this tendency were combined, resulting in a molecule that was both magnetic and strongly attracted to dopamine.
The team injected the molecule into the brains of rats, in a region laden with dopamine-producing celis. When given a chemical that triggers dopamine release, that area "lit up" under fMRI (Nature Biotechnology, 001: 1O.103B/nbt.1609). Because the molecule must be injected into the brain, this kind of chemical- based fMRI won't be applied to humans anytime soon, says jasan off. b u t it could be used to probe addiction and disease using animals. His lab is now using the enzyme to view how dopamine-sensitive neurons across animal brains react when the chemical is produced in a specific region. The technique could also be used to probe dopamine's role in diseases such as Huntington's. The magnetic enzyme can in theory b e "evolved" t o b i n d t o other brain chemicals. Ewen Callaway
Source of Information : New Scientist March 6 2010