The part of the brain that controls addictive behaviour – the infralimbic cortex – can be reprogrammed to ease cocaine urges in addicts, a new study has shown. In a series of experiments, scientists from the University of Iowa in the US, gave rats cocaine when they pressed a lever with their paws.
The rats did so for two hours a day for two weeks. After that, the rats received no cocaine when they pressed the lever.
When they realised that they were no longer getting the drug, the rats pressed the lever less frequently, until by the end of a two-week period, they hardly pressed the lever at all.
A second group of rats followed the same regimen as the control group. However, in the second group, the researchers turned off neurons in the rats’ infralimbic cortex just as the animals pressed the drug-dispensing lever. By silencing those neurons for a period of 20 seconds every time the rats pressed the lever, the researchers prevented the rats from learning to curb their drug appetite.
The rats’ cravings remained as intense as in the beginning of the experiment, even though they weren’t receiving the drug. The researchers silenced the neurons in the rats’ brains for the first five days of the two-week period without cocaine. They found that these five days had a major impact on how effectively rats learnt and began to adapt to the drug’s absence.
The rats whose neurons were silenced were more likely to relapse than those that underwent withdrawal. The results strengthen the hypothesis that the infralimbic cortex plays an important role in the suppression of addictive behaviour. It also points to when the region could best be “taught” to curb a habit.
“No study has looked intensively at exactly how the infralimbic cortex functions, nor the importance of the first five days of treatment when it comes to curtailing drug-seeking behaviour. And while our experiments involved cocaine, we think the results could hold true for the infralimbic cortex’s role in conditioning withdrawal and relapse from other addictive substances, including opioids,” said Ryan LaLumiere, the study’s co-author.
The findings, which were published in the Journal of Neuroscience, could help drug addicts kick the habit with the help of drugs that target the infralimbic cortex to temper impulses and control cravings – or with improved behavioural treatment for substance addiction and relapse.