Rat study suggests why teens get hooked on cocaine more easily t...(researchers let the rats freely explore ...),Health

Date:4/21/2008

researchers let the rats freely explore the entire apparatus in a drug-free state for 30 minutes, to test for conditioned place preference for the chamber where they got cocaine. Brenhouse and Andersen calculated how long each rat spent in the drug-paired side relative to total time spent on either side. They repeated the procedure every 24 hours until each animals place preference was extinguished, when the time they spent in the drug-paired chamber was cut in half suggesting no lingering preference for either side.

Relative to adults, adolescent rats required around 75 percent more trials to extinguish a preference for the place where they were given the drug.

After each rats last extinction trial, the researchers waited 24 hours, injected a low 5 mg/kg priming dose of cocaine, and put it back in the apparatus to test for place preference. During this test for reinstatement of extinguished preferences, adolescent rats showed a significantly greater renewed preference than did adults for the drug-paired chamber. Those that had originally learned on a 10 mg/kg dose of cocaine showed 40 percent greater reinstatement than the few adult rats that showed a place preference at the lower dose.

Interestingly, both adolescent and adult rats who were conditioned at the 20 mg/kg dose renewed their place preference to a similar degree. Brenhouse and Andersen view this as a sign that adolescents form stronger memories for even less potent rewards. Thus, they wrote, Adolescent vulnerability to addiction involves robust memories for drug-associated cues that are difficult to extinguish. They speculate that the context of drug use is more salient to adolescents, perhaps because the frontal cortex is still developing.

Brenhouse and her fellow researchers found in prior studies that during adolescence, dopamine a neurotransmitter that signals reward may trigger more focused messages traveling from the frontal-cortex area involved with lea
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Contact: Public Affairs Office public.affairs@apa.org 202-336-5700 American Psychological Association Source:Eurekalert

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