| In humans, adolescence is a period of heightened propensity to develop cocaine addiction. We used preclinical models to examine the nature of this observation.;Adolescent (postnatal day 42) and adult (∼postnatal day 88) rats were compared for cocaine addiction liability according to DSM-IV criteria, using intravenous self-administration. In Chapter 1, we show that relative to adults, adolescents took cocaine more readily, escalated cocaine intake, and worked harder for cocaine. This was associated with elevated activity of midbrain dopamine neurons, as measured with in vivo extracellular recordings. When elevated activity of dopamine neurons was suppressed pharmacologically, adolescent cocaine intake decreased to adult-like levels. This provides insight into neural mechanisms of adolescent addiction liability, by highlighting dopamine neurons as a key element of addiction risk.;The next question to ask is: are adolescents more likely to remain addicted to cocaine compared with adults? In Chapter 2, we tested how punishment (electric footshock) associated with drug intake affects drug use. Cocaine intake was suppressed for both ages on the day of punishment. However, on the next day, adolescents resumed cocaine taking whereas adults did not. Next, in Chapter 3 we tested the long-term consequence of drug use by examining relapse in response to different stressors. Relapse was far more pronounced if onset of cocaine use occurred during adolescence vs. adulthood.;Our research is the first to offer scientific evidence that when all opportunities to take drugs are equal, adolescents are more prone to cocaine addiction compared with adults. Importantly, adolescents do not refrain from taking cocaine after punishment and they are more likely to relapse in response to stress later on in life. These results have broad implications for the attempts to steer adolescents away from drug use using punishments as well as for preventing relapse. |
