The chronic relapsing nature of cocaine addiction suggests that chronic cocaine exposure produces persistent neuroadaptations that may be temporally and regionally dynamic in brain areas such as the dopaminergic (DA) system. We have previously shown altered metabolism of DA-target structures, the ventral and dorsal striatum, between early and late abstinence. However, specific changes within the midbrain DA system were not investigated. Here, we investigated potential time- and region-specific changes of activity in the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNc) in rats that had extended or limited access to cocaine and later underwent a period of abstinence. We found that DA activity is decreased only in the VTA in rats with extended access to cocaine, with no changes in SNc DA activity. These changes in VTA DA activity may participate in the negative emotional state and the incubation of drug seeking that occur during abstinence from cocaine.

中文翻译：

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延长可卡因自我给药的长期禁欲与 VTA 中的低多巴胺能活动有关，但与 SNc 无关

可卡因成瘾的慢性复发性质表明，长期接触可卡因会产生持续的神经适应，这些神经适应可能在大脑区域如多巴胺能 (DA) 系统中具有时间和区域动态。我们以前已经表明 DA 目标结构的代谢改变，腹侧和背侧纹状体，在早期和晚期禁欲之间。然而，没有研究中脑 DA 系统内的特定变化。在这里，我们调查了大鼠腹侧被盖区 (VTA) 和黑质致密部 (SNc) 活动的潜在时间和区域特异性变化，这些大鼠已经延长或有限地接触可卡因，后来经历了一段时间的禁欲。我们发现 DA 活性仅在长期接触可卡因的大鼠的 VTA 中降低，而 SNc DA 活性没有变化。