One characteristic feature of addictive drugs is their ability to induce, after a single exposure, a lasting sensitization to the next doses; the underlying neuroplastic changes supposedly involve the brain dopamine system. We aimed at identifying putative relationships between alterations in extracellular dorsal striatal dopamine, HVA and DOPAC levels and in frequency-modulated 50-kHz ultrasonic vocalizations rate response during repeated intraperitoneal amphetamine treatment. Measurements were performed before and after amphetamine doses 1, 2, 7 and 8 (Amph1, Amph2, Amph7 and Amph8; treatment days 1, 7, 12 and 23, respectively). Amphetamine was confirmed to induce sensitization of the vocalization response, but an extended recording time (180 instead of 20 min) revealed that sensitization of this response requires more time to develop than hitherto believed. Baseline extracellular dopamine level increased initially, declined after a series of daily amphetamine doses and showed some tendency for recovery after drug withdrawal. Baseline extracellular DOPAC (but not HVA) showed a continuous decline during the treatment. There was no significant change in the integrated short-term (3-h) extracellular dopamine response, whereas the respective DOPAC collection lowered significantly after repeated drug treatment. Extracellular DOPAC is believed to originate mostly from newly synthesized dopamine, hence the declines in its baseline and post-amphetamine levels suggest falling dopamine synthesis. These results indicate that sensitization of the appetitive vocalization response to amphetamine continues despite reduced dorsal striatal dopamine synthesis and involves no changes in amphetamine-induced dopamine release.

成瘾药物的一个特征是它们能够在单次接触后诱导对下一次剂量的持久致敏；据推测，潜在的神经可塑性变化涉及大脑多巴胺系统。我们旨在确定在重复腹膜内安非他明治疗期间细胞外背侧纹状体多巴胺、HVA 和 DOPAC 水平的改变与调频 50 kHz 超声发声速率响应之间的假定关系。在苯丙胺剂量 1、2、7 和 8（Amph1、Amph2、Amph7 和 Amph8；分别为治疗第 1、7、12 和 23 天）之前和之后进行测量。安非他明被证实能诱导发声反应的敏化，但是延长的记录时间（180 分钟而不是 20 分钟）表明，这种反应的敏感化需要比迄今为止认为的更多的时间来发展。基线细胞外多巴胺水平最初增加，在一系列每日安非他明剂量后下降，并在停药后显示出一些恢复趋势。基线细胞外 DOPAC（但不是 HVA）在治疗期间显示出持续下降。综合短期（3 小时）细胞外多巴胺反应没有显着变化，而重复药物治疗后各自的 DOPAC 收集显着降低。细胞外 DOPAC 被认为主要来自新合成的多巴胺，因此其基线和苯丙胺后水平的下降表明多巴胺合成下降。