Tepper J M, Creese I, Schwartz D H
Center for Molecular and Behavioral Neuroscience, Aidekman Research Center, Rutgers, State University of New Jersey, Newark 07102.
Brain Res. 1991 Sep 20;559(2):283-92. doi: 10.1016/0006-8993(91)90013-l.
The effect of medial forebrain bundle (MFB) stimulation on neostriatal dopamine levels was examined using in vivo microdialysis in urethane-anesthetized and awake, freely-moving rats in conjunction with single unit extracellular recordings from antidromically identified nigral dopaminergic neurons. Dialysis samples were collected during baseline periods or while stimulating the MFB with trains of 5 or 10 pulses at different frequencies within a physiologically relevant range. When the perfusion solution contained 1.2 mM Ca2+, even intense, high frequency stimulation was ineffective at producing significant elevations in neostriatal dopamine levels whereas cocaine or amphetamine reliably caused several-fold elevations in dopamine levels. When the perfusate contained 2.4 mM Ca2+, modest MFB stimulation within the range of spontaneous nigral cell firing produced large and reliable increases in dopamine levels. There was a significant correlation between the proportion of dopaminergic neurons that could be antidromically activated from the MFB and the increase in neostriatal dopamine. There was no effect of stimulus pattern on the increase in dopamine levels, and results obtained in awake, freely-moving animals did not differ from those obtained in anesthetized animals. These data provide good evidence that in vivo microdialysis is sensitive to neostriatal dopamine overflow evoked by stimulation within the normal rate of firing of nigrostriatal neurons and that Ringer's Ca2+ concentration is a critical variable in the detection of stimulus-induced release of dopamine.
运用体内微透析技术，结合对经逆向鉴定的黑质多巴胺能神经元进行的单单位细胞外记录，在乌拉坦麻醉的以及清醒、自由活动的大鼠中，研究了内侧前脑束（MFB）刺激对新纹状体多巴胺水平的影响。在基线期或在生理相关范围内以不同频率用5或10个脉冲的串刺激MFB时，收集透析样本。当灌注液含有1.2 mM Ca2+时，即使是强烈的高频刺激也无法使新纹状体多巴胺水平显著升高，而可卡因或苯丙胺能可靠地使多巴胺水平升高数倍。当灌注液含有2.4 mM Ca2+时，在黑质细胞自发放电范围内适度刺激MFB会使多巴胺水平产生大幅且可靠的升高。能够从MFB逆向激活的多巴胺能神经元比例与新纹状体多巴胺的增加之间存在显著相关性。刺激模式对多巴胺水平的升高没有影响，并且在清醒、自由活动动物中获得的结果与在麻醉动物中获得的结果没有差异。这些数据充分证明，体内微透析对黑质纹状体神经元正常放电速率范围内的刺激所诱发的新纹状体多巴胺溢出敏感，并且林格氏液中的Ca2+浓度是检测刺激诱导的多巴胺释放的关键变量。
