Researchers at the University of Texas at Austin (UT) have discovered a potential indicator of future substance abuse and addiction.
The study, published this week in the journal Neuron, detailed the researchers findings after having created a social isolation scenario with laboratory rats. They were able to determine that the isolation, presented during the critical period of adolescence, led to an increased vulnerability to addiction of both alcohol and amphetamines. They also determined that an addiction to amphetamine was more difficult to eradicate in the population of rats that experienced the adolescent social isolation and that the addiction effect persisted well after the rats had been reintroduced to the community of other rats.
“Basically the animals become more manipulatable,” said Hitoshi Morikawa, associate professor of neurobiology in the College of Natural Sciences. “They’re more sensitive to reward, and once conditioned the conditioning takes longer to extinguish. We’ve been able to observe this at both the behavioral and neuronal level.”
According to Mickaël Degoulet, a postdoctoral researcher in Morikawa’s lab, the results were striking. The team found the subject rats were much more apt to form a preference for the small, distinctive box from which amphetamine and alcohol were received than were their peers in the control group who did not experience isolation. In fact, the isolated rats presented a preference after just one exposure to either drug while the control rats required repeated exposure to the substances to display a conditioned behavior response.
The researchers, according to Morikawa, believed this kind of preference for the environmental context in which the reward was received provided them with a more useful way of understanding addiction rather than seeing it as a desire for more of the addictive substance. “So the social isolation leads to addiction more quickly, and it’s harder to extinguish,” said Leslie Whitaker, a former doctoral student in Morikawa's lab, and now a researcher at the Natoinal Institute on Drug Abuse.