Adult male monkeys exposed to cocaine while in the womb have poor impulse control and may be more vulnerable to drug abuse than female monkeys, even a decade or more after the exposure, according to a new study by researchers at Wake Forest University School of Medicine. The findings could lead to a better understanding of human drug abuse.
The study was presented today at the annual Society for Neuroscience meeting in Chicago.
“This is the first time that so many different measures of impulsivity, which is considered a risk factor for drug abuse, have been looked at in the same group of animals,” said Lindsey Hamilton, lead investigator and a graduate student working in the laboratory of Michael Nader, Ph.D., a professor of physiology and pharmacology. “We’re looking for ways to predict which individuals are going to take drugs during their lives. It was very surprising to see that, even more than a decade after the prenatal cocaine exposure, the monkeys ended up being more impulsive and possibly more susceptible to drug use. It was particularly interesting, however, that this effect was only seen in the males. Something is either protecting the females from the effects of the cocaine exposure in the womb or making the males more susceptible to the lasting effects.”
For the study, researchers compared adult monkeys – both male and female – prenatally exposed to cocaine more than 15 years ago, to monkeys who were raised under similar conditions, but not exposed to cocaine during gestation. To determine if the animals differed in impulse control, they performed four tests. For one of the tests, the researchers gave the animals the choice between pushing a lever that delivered a single banana pellet reward immediately or a lever that delivered several banana pellets, but required the animals to wait up to five minutes before the reward was delivered.
“That’s where we saw very large differences between the groups,” Hamilton said. “The males who were exposed to cocaine in-utero had no patience or impulse control whatsoever.”
Those monkeys were less willing to wait for a larger food reward and preferred the immediately available, though much smaller, reward, indicating they were more impulsive than the adult male monkeys who had never been exposed to cocaine. There was, however, no difference in the preference of female monkeys prenatally exposed to cocaine and those never exposed to the drug.
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