Vulnerability to relapse after drug withdrawal is a central problem in treating drug addiction. Exposure to drugs, or even to cues that remind addicts of drug use, can trigger relapse. Mu-ming Poo and colleagues now describe a mechanism in the brain that may contribute to the cue-triggered drug seeking during abstinence in the May 2006 issue of Nature Neuroscience.
The authors studied a brain area called the ventral tegmental area (VTA) known to be involved in reward and reinforcement associated with drug addiction. During a period of cocaine withdrawal in rats previously given daily cocaine injections for 5-7 days, they found that synapses onto dopamine-releasing neurons showed a heightened susceptibility to increase in strength, so that even weak stimulation could cause long-lasting increases in the neurons' responses. This enhanced plasticity required a growth factor called BDNF, which has previously been linked to drug-seeking behavior after withdrawal.
Drug craving and relapse may involve a specific enhancement of reward signals in response to drug-associated cues. The results described by Poo and colleagues suggest a mechanism that might allow for such enhancement.
Mu-ming Poo (University of California, Berkeley, CA)
Abstract available online.
(C) Nature Neuroscience press release.
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