As if mimicking a human reaction, adolescent mice are more sensitive to addictive drugs than either infant or adult mice, according to the results of a recent study published in the Journal of Neuroscience (1 November 2002).
Although illicit drug use sharply increases during human adolescence, there is little information about the molecular mechanisms that may underlie this phenomenon. Now, Michelle E. Ehrlich of the Nathan Kline Institute (Orangeburg, NY) and New York University School of Medicine (New York, NY) and colleagues report the results of giving post-weanling (24-day-old), periadolescent (33-day-old), and adult (60-day-old) mice intraperitoneal injections of cocaine or amphetamine daily for seven days. The team measured protein levels in the mouse brains and found that chronic exposure to these psychostimulants was associated with a greater increase in levels of the transcription factor ΔFosB in the brains of periadolescent mice, compared to post-weanlings or adults. These increases occurred specifically in the brain regions associated with motor activity and the reward system. This is the first study to compare neurochemical responses of animals to psycho-stimulants at different ages. The results may help explain the unique responses of the adolescent brain to psychostimulants.