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Research Fellow Jane Stewart talks about why drugs are harder to quit than we thought


Photo of Prof. Jane Stewart

Professor Jane Stewart at the reception following her lecture as Concordia University Fellow.


by Sigalit Hoffman

Prolonged drug use changes the structure of the brain, making our efforts to quit for good more difficult. That’s the essence of the message delivered in a public lecture at the downtown Faculty Club on September 21 by Psychology Professor Jane Stewart.

In her work as a senior researcher with the Centre for Studies in Behavioural Neurobiology (CSBN), Stewart has been able to show that sensitivity to drugs — and thus, the chance of relapse — is at its highest some time after drug use has ceased. This brings into question the common belief that craving and relapse are strongest shortly after quitting.

She explained that chronic drug use eventually leads to changes in the brain that increase the individual’s sensitivity to drugs. On re-exposure to the drug, this heightened sensitivity induces renewed craving and a high probability of relapse. Stewart admitted, “This is really quite pessimistic for drug treatment. Just being away from it is not good enough.”

Sensitization to drugs could be prevented

She shed some light on the biological basis of the changes in brain structure. She noticed that the brains of rats sensitized to the stimulant drug amphetamine had four times the normal amount of a neurotrophic factor known to be associated with growth and repair.

Neurotrophic factors are compounds that are present in the brain at birth and are responsible for the growth, extension, and guiding of neurons to their targets. They are also present in adult brains and may be increased in brains undergoing trauma. By giving rats an agent that neutralized the effect of the neurotrophic factor, she found that sensitization to drugs could be prevented.

Stewart illustrated the long-term effects of brain changes in her conditioning experiments. Rats were taught to associate cocaine with a particular cage, and then this association was reduced by replacing the drug injections by injection of saline.

As soon as the animals were re-administered the drug, they preferred the cage that they had previously associated with cocaine. These data emphasize the importance of conditioned stimuli, in this case the environment, in relapse. She explained how an initially aversive stimulus can be made attractive by pairing it with a pleasurable effects of a drug, such as alcohol. “Think of the initially nasty taste of pure malt whiskey,” she said.

Drugs may not initially be attractive, but when associated with the feelings they create, they become highly sought. In addition, Stewart pointed to stress as another potential cause of relapse. Stressed animals, she discovered, exhibit a greater desire for drugs.
In her lab animals, Stewart has observed that the drugs that have effects on the brain similar to those of important natural stimuli — such as food and sexual partners — are the same ones that animals, including humans, will self-administer.

She spoke of the bi-directional effects of her research approach. She said, for example, that “by studying the motivational systems of the brain activated by natural incentives, we found something about how drugs work, but [at the same time,] we can use drugs as tools to find out how the motivational systems work.”

Copyright 2000, Concordia University