Addictions to medicines and drugs are thought to develop over a relatively long period of time. The process involves both structural and functional changes in brain nerve cells that are still poorly understood. However, a single drug or alcohol dose is sufficient to generate an initial stage of addiction. Recent research conducted under the umbrella of the Academy of Finland Research Programme on Neuroscience (NEURO) has discovered the same phenomenon in the dosage of benzodiazepine diazepam.
Benzodiazepines are highly effective medicines that are widely used in the treatment of anxiety, insomnia, pains, panic attacks and other symptoms. However, over time patients may develop an increased tolerance towards these medicines and an unhealthy dependence.
"Previously, addiction to benzodiazepines has been explained by reference to negative rather than positive reinforcement. In other words, the thinking has been that the reason people continue to use the medicine is that it helps to alleviate their distressing withdrawal symptoms and general discomfort, rather than because it provides a sense of reward," says Professor Esa Korpi, who has been in charge of the research project at the University of Helsinki.
However, according to the latest research it seems that diazepam causes a similar change in the brain's reward-inducing dopamine cells as a dose of alcohol, morphine, amphetamine or cocaine. Furthermore, neural message transmission in the dopamine cells is reinforced for up to 72 hours after ingestion of diazepam. "Our studies have shown that diazepam also affects the dopamine system, which adds a new positive reinforcement mechanism of reward learning to the theory of benzodiazepine addiction," Korpi explains.
Article published on the subject in Neuropsychopharmacology, 18 June 2008:
Long-lasting modulation of glutamatergic transmission in VTA dopamine neurons after a single dose of benzodiazepine agonists.
The Academy's ongoing Research Programme on Neuroscience NEURO (www.aka.fi/neuro) is scheduled to run from 2005 to 2009. The programme is conducted jointly with Chinese and Canadian partners. Its purpose is to support multidisciplinary neuroscience research at the highest level and to promote cooperation, networking and mobility among scientists from the countries involved in the programme.
More information:
Professor Esa Korpi, University of Helsinki, tel. +358 9 191 25330, esa.korpi(at)helsinki.fi
Researcher Anne Heikkinen, University of Helsinki, tel. +358 9 191 25340, anne.heikkinen(at)helsinki.fi
Journal
Neuropsychopharmacology