Dey S, Mactutus C F, Booze R M, Snow D M
Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY 40536-0298, USA.
Neuroscience. 2006;139(3):899-907. doi: 10.1016/j.neuroscience.2005.12.053. Epub 2006 Feb 17.
Prenatal cocaine exposure induces alterations in attentional function that presumably involve locus coeruleus noradrenergic neurons and their projections. Previous reports indicate that embryonic rat locus coeruleus neurons exposed to cocaine, both in vitro and in vivo, showed in decreased cell survival and inhibition of neurite outgrowth, and that the effects were most deleterious during early gestation. The present study performed in vitro addressed the specificity of the inhibitory effects of cocaine by comparing locus coeruleus neurite formation and extension to that of dopaminergic substantia nigra neurons following exposure to a physiologically-relevant dose of cocaine (500 ng/ml, two times a day, for four days) during peak neuritogenesis. Following cocaine treatment, immunocytochemistry (anti-norepinephrine antibody to locus coeruleus; anti-tyrosine hydroxylase antibody to substantia nigra) and image analysis were performed to measure a variety of neurite outgrowth parameters. For locus coeruleus neurons, cocaine treatment decreased the 1) number of cells initiating neurites [P<0.001], 2) mean number [P<0.05] and length of neurites [P<0.0001], 3) mean number [P<0.0016] and length of branched neurites [P<0.0006], and 4) mean length of the longest neurites [P<0.0001]. In comparison, substantia nigra neurons were not significantly affected by cocaine for any of the parameters examined. More importantly, a significant interaction between cocaine treatment and brain region was observed [P<0.0002] indicating greater vulnerability of locus coeruleus, relative to substantia nigra neurons, to cocaine exposure. These data support our hypothesis that cocaine targets the noradrenergic system by negatively regulating locus coeruleus neuronal outgrowth, which likely affects pathfinding, synaptic connectivity, and ultimately attentional behavior in cocaine-exposed offspring.
产前接触可卡因会引起注意力功能的改变，这可能涉及蓝斑去甲肾上腺素能神经元及其投射。先前的报告表明，体外和体内接触可卡因的胚胎大鼠蓝斑神经元，其细胞存活率降低且神经突生长受到抑制，并且这些影响在妊娠早期最为有害。本研究在体外进行，通过比较在神经突发生高峰期接触生理相关剂量可卡因（500 ng/ml，每天两次，共四天）后，蓝斑神经突形成和延伸与多巴胺能黑质神经元的情况，探讨了可卡因抑制作用的特异性。可卡因处理后，进行免疫细胞化学（针对蓝斑的抗去甲肾上腺素抗体；针对黑质的抗酪氨酸羟化酶抗体）和图像分析，以测量各种神经突生长参数。对于蓝斑神经元，可卡因处理降低了：1）开始产生神经突的细胞数量[P<0.001]，2）神经突的平均数量[P<0.05]和长度[P<0.0001]，3）分支神经突的平均数量[P<0.0016]和长度[P<0.0006]，以及4）最长神经突的平均长度[P<0.0001]。相比之下，黑质神经元在所检查的任何参数上均未受到可卡因的显著影响。更重要的是，观察到可卡因处理与脑区之间存在显著相互作用[P<0.0002]，表明相对于黑质神经元，蓝斑对可卡因暴露更易受损。这些数据支持了我们的假设，即可卡因通过负向调节蓝斑神经元的生长来靶向去甲肾上腺素能系统，这可能会影响可卡因暴露后代的路径寻找、突触连接，最终影响注意力行为。
