We have initiated studies investigating how the juvenile brain differs from the adult brain in the medial prefrontal cortex. Recent evidence has shown that the medial prefrontal cortex (mPFC) is an important brain area in the control of impulsivity and decision-making. The neurotransmitters serotonin (5-HT) and dopamine (DA) are integral to the function of the mPFC and are increased by the drugs used therapeutically to treat attentioanl deficit disorder, i.e. methylphenidate and methamphetamine. The purpose of our investigation was to determine the extracellular concentrations of DA and 5-HT in the mPFC of adolescent and adult rats. Because some studies have shown differences between the left and right mPFC in terms of extracellular 5-HT and DA we have used dual probes to examine both left and right mPFC. The overlying hypothesis is the juvenile brain of the rat has a decreased extracellular dopamine and norepinephrine and an increased serotonin. This would be in keeping with findings that low dopamine or norepinephrine and/or high serotonin lead to impulsive behaviors. Dual microdialysis probes (2 mm) were placed into the left and right ventral mPFC of adolescent (postnatal day 40-45) and adult (postnatal day 90). Following collection of baseline samples, 100 microM methamphatamine was perfused through the probes for 1 hr. Microdialysate was analyzed for DA and 5-HT via HPLC. Our preliminary findings show that basal extracellular levels of 5-HT and DA are the same in the left and right ventral mPFC in adolecent male rats. In contrast, there was a laterality in the extracellular levels of 5-HT and DA in adult male animals. Methamphetamine increased the extracellular levels of 5-HT and DA in both adolescent and adult rats. These data suggest that there are differences between adolescent and adult rats in the basal release of serotonin and dopamine in the ventral mPFC. This may relate to the impulsivity and attentional differences between adolescents and adults