Michler A
Center of Anatomy, University of Goettingen, F.R.G.
Int J Dev Neurosci. 1990;8(4):463-72. doi: 10.1016/0736-5748(90)90078-g.
Modulation of neurite growth by gamma-aminobutyric acid (GABA) and several agonists and antagonists to its receptors was analysed in neuronal cultures of embryonic chick tectum and rat cerebellum, respectively, using morphometric methods. In each case, modulation of growth by GABA was similar in both types of neurons. However, data on neurite elongation suggest differential effects depending on the culture medium used. In serum-containing medium GABA stimulated neurite growth. In serum-free, defined medium the opposite effect was observed, i.e. GABA inhibited neurite elongation in tectal as well as in cerebellar cultures. When agonists of the GABAA-receptor were employed stimulation of neurite outgrowth was observed in serum-supplemented medium but not in serum-free medium. These ligands could not influence the inhibition of neurite growth caused by GABA. In contrast, the GABAB-receptor agonist (-)baclofen inhibited neurite elongation in serum-free medium without affecting cells in the presence of serum. Phaclofen, a GABAB-receptor antagonist, induced quite the opposite effect. It stimulated neurite elongation in serum-free culture conditions and prevented the inhibition induced by GABA in a concentration-dependent manner. In serum-supplemented medium it had no effect. The data suggest that GABAA-receptors may be involved in the GABA-induced neurite elongation in serum-supplemented medium only, although this subtype of receptors is present in serum-free conditions as well as revealed in binding studies using [3H]muscimol. Whether GABAB-receptors and/or as yet undefined mechanisms are responsible for the different action of GABA in serum-free medium is subject of further investigations.
分别使用形态测量方法，在胚胎鸡顶盖和大鼠小脑的神经元培养物中分析了γ-氨基丁酸（GABA）及其几种受体激动剂和拮抗剂对神经突生长的调节作用。在每种情况下，GABA对两种类型神经元生长的调节作用相似。然而，关于神经突伸长的数据表明，其作用效果因所用培养基的不同而有所差异。在含血清的培养基中，GABA刺激神经突生长。而在无血清的限定培养基中则观察到相反的效果，即GABA抑制顶盖和小脑培养物中的神经突伸长。当使用GABAA受体激动剂时，在补充血清的培养基中观察到神经突生长受到刺激，但在无血清培养基中则未观察到这种现象。这些配体不会影响GABA对神经突生长的抑制作用。相反，GABAB受体激动剂（-）巴氯芬在无血清培养基中抑制神经突伸长，而在有血清存在的情况下对细胞无影响。GABAB受体拮抗剂法氯芬则产生完全相反的效果。它在无血清培养条件下刺激神经突伸长，并以浓度依赖的方式阻止GABA诱导的抑制作用。在补充血清的培养基中，它没有作用。数据表明，GABAA受体可能仅参与补充血清的培养基中GABA诱导的神经突伸长，尽管这种受体亚型在无血清条件下也存在，并且在使用[3H]蝇蕈醇的结合研究中也得到了证实。GABAB受体和/或尚未明确的机制是否负责GABA在无血清培养基中的不同作用，还有待进一步研究。
