NEUROCHEMISTRY:
Teaching the Brain to Take Drugs
Ingrid Wickelgren
New evidence is indicating that, along with dopamine, another neurotransmitter, glutamate, may contribute to the learning of addictive behavior by producing long-term, stable changes in the brain that lead to compulsive drug-seeking. Researchers have found, for example, that blocking glutamate transmission in rats prevents behavioral sensitization, in which repeated doses of amphetamine or cocaine make the animals increasingly frantic and more likely to engage in purposeless motions; this may parallel the increasing anxiety and drug craving that humans feel after repeated hits of amphetamine or cocaine. Scientists have also identified lasting cellular and molecular changes that seem to increase activity in the brain's glutamate circuitry in animals given cocaine; brain imaging studies in humans have buttressed the theory that these circuits may be reactivated during drug cravings. If the notion that glutamate plays such a critical role in addiction holds true, drugs that block glutamate activity could one day help addicts kick their habit.
