| Summary: | 碩士 === 國立政治大學 === 神經科學研究所 === 106 === Impulsive behavior has been considered to be related to several mental disorders including drug addiction. Individuals with abnormally high level of impulsivity are usually more likely to have drug addiction. This study used a differential reinforcement of low-rate response (DRL) task to investigate impulsive action that could be related to conditioned place preference (CPP) and behavioral sensitization (BS) as induced by amphetamine. Western blotting was used to analyze four proteins, dopamine D1 and D2 receptors, dopamine transporter (DAT) and brain-derived neurotrophic factor (BDNF), expressed in five brain regions relevant to the midbrain dopamine systems after psychopharmacological test. The results show that the subjects (n=47 or 48) in each of three batches trained in a DRL 10-sec task for 14 (or 17), based on the response efficiency, can be sorted by a quartile method into three groups with different levels of impulsivity (i.e., high, intermediate and low). The between-group difference was also confirmed on each of six measures of the present DRL behavior. Data of Experiment 1-1 and Experiment 1-2 together showed significant CPP induced by amphetamine; however, it was not correlated to the individual differences of DRL behavior. Biochemical assay of Experiment 1-2 revealed that amphetamine had different effects on the four proteins in the five brain regions, but these effects were not statistically correlated with behavioral responses of DRL. The results of Experiment 2 showed that the individual differences of DRL behavior were significantly correlated to the effects of amphetamine-induced BS. The low impulsive subjects had a weaker drug-induced BS and vice versa. Biochemical assay of Experiment 2 showed that there was a positive correlation between the amount of D1 receptors expressed in the dorsal striatum and the efficiency of DRL behavior; and in the dorsal striatum and the hippocampus, there was a positive correlation between the DAT and the BS induced by amphetamine. Together, the individual differences of impulse action assessed by DRL behavior can be used to predict the varied magnitudes of BS, but not CPP, induced by amphetamine. And, distinctive neural substrates are involved in psychopharmacological effects of CPP and BS induced by amphetamine.
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