Zhang Tianxiang, Zhang Lifen, Liang Yong, Siapas Athanassios G, Zhou Fu-Ming, Dani John A
Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030-3498, USA.
J Neurosci. 2009 Apr 1;29(13):4035-43. doi: 10.1523/JNEUROSCI.0261-09.2009.
The dorsal striatum and the nucleus accumbens (NAc) shell of the ventral striatum have similar cellular components and are both richly innervated by dopamine neurons. Despite similarities that extend throughout the striatum, only the NAc shell has a conspicuous increase in basal dopamine upon the initial administration of psychostimulant drugs such as nicotine. As measured by microdialysis, the elevated dopamine in the NAc shell is considered an identifying functional characteristic of addictive drugs. To examine this general functional difference between nicotine's action on the dorsolateral striatum and NAc shell, we directly monitored dopamine release in rat striatal slices using fast-scan cyclic voltammetry. In addition, we separately monitored the in vivo unit firing activity of putative midbrain dopamine neurons from freely moving rats using chronic multiple tetrodes. Nicotine administration increased the firing frequency of dopamine neurons and specifically increased the number and the length of phasic burst firing. The frequency dependence for dopamine release in the dorsolateral striatum and NAc shell is fundamentally different, enabling mainly the NAc shell to capitalize on the nicotine-induced phasic burst firing by dopamine neurons. Although nicotine decreased low-frequency (tonic) dopamine release in both areas, the increased ratio of phasic bursts relative to tonic firing caused by nicotine boosted the basal dopamine concentration predominantly in the NAc shell. By favoring release from bursts while depressing release from tonic signals, nicotine spreads the range of dopamine signaling and effectively increases the signal-to-noise relationship along dopamine afferents.
背侧纹状体和腹侧纹状体的伏隔核（NAc）壳具有相似的细胞成分，并且都接受多巴胺神经元的丰富支配。尽管整个纹状体存在相似之处，但只有NAc壳在初次给予尼古丁等精神兴奋药物时，基础多巴胺会有明显增加。通过微透析测量，NAc壳中多巴胺的升高被认为是成瘾药物的一个标志性功能特征。为了研究尼古丁对背外侧纹状体和NAc壳作用的这种一般功能差异，我们使用快速扫描循环伏安法直接监测大鼠纹状体切片中的多巴胺释放。此外，我们使用慢性多电极分别监测自由活动大鼠中假定的中脑多巴胺神经元的体内单位放电活动。给予尼古丁会增加多巴胺神经元的放电频率，并特别增加相位爆发放电的数量和时长。背外侧纹状体和NAc壳中多巴胺释放的频率依赖性存在根本差异，这使得主要是NAc壳能够利用多巴胺神经元尼古丁诱导的相位爆发放电。尽管尼古丁在两个区域都降低了低频（紧张性）多巴胺释放，但尼古丁引起的相位爆发相对于紧张性放电的增加比例主要提高了NAc壳中的基础多巴胺浓度。通过促进爆发性释放同时抑制紧张性信号的释放，尼古丁扩展了多巴胺信号的范围，并有效地增加了沿多巴胺传入纤维的信噪比。
