Miranda-Contreras L, Benítez-Diaz P R, Mendoza-Briceño R V, Delgado-Saez M C, Palacios-Prü E L
Electron Microscopy Center, University of Los Andes, Caracas, Venezuela.
Dev Neurosci. 1999;21(2):147-58. doi: 10.1159/000017377.
The variation in the levels of excitatory (glutamate and aspartate) and inhibitory (GABA, glycine and taurine) neurotransmitters during neurogenesis in mouse cerebellum, from embryonic day (E) 15 until the young adult stage, was analyzed by high-pressure liquid chromatography. Between E15 and E21, high contents of GABA, glutamate and aspartate were detected, with the GABA levels approximately 2- to 3-fold higher than those of glutamate and aspartate. After birth, the levels of GABA remained high during the first 2 postnatal weeks and then reached a plateau comparable to adult values by the third week. The levels of glutamate and aspartate increased gradually from birth to the young adult stage, showing peak values at postnatal days (P) 3 and P11. Glycine and taurine were present at relatively low concentrations during the prenatal period, then rose significantly by about 4-fold after birth; their levels decreased by the end of the first postnatal week but increased gradually thereafter until reaching adult values by the third week. To determine the endogenous neurotransmitter production in the cerebellar cortex, primary histotypic cerebellar cultures prepared at P10 were analyzed and the in vitro transmitter contents were compared with the adult in situ values. The cultures showed about the same levels of glutamate and aspartate; however, their concentrations were lower by half than in vivo, suggesting that both play an equally important role in the excitatory neurotransmission of the cerebellar cortex internal circuitry pathways and that in mature cerebellum, about 50% of the excitatory synaptic inputs derive from the afferent climbing and mossy fibers. The in vitro GABA and glycine contents were comparable with the in vivo levels, whereas the taurine concentrations were about 5-fold lower in vitro than in vivo. These findings indicate that most of the GABA and glycine transmitters are produced intrinsically while a high proportion of taurine in the cerebellum comes from extracerebellar afferents. This study provides data on the changing levels of the amino acid neurotransmitters in developing mouse cerebellum and the relative proportions of neurotransmitter contents that are produced by intrinsic neurons in contrast to those derived from extrinsic afferent fibers.
通过高压液相色谱法分析了小鼠小脑从胚胎期第15天（E15）直至年轻成年期神经发生过程中兴奋性（谷氨酸和天冬氨酸）和抑制性（γ-氨基丁酸、甘氨酸和牛磺酸）神经递质水平的变化。在E15至E21期间，检测到γ-氨基丁酸、谷氨酸和天冬氨酸含量较高，γ-氨基丁酸水平比谷氨酸和天冬氨酸高约2至3倍。出生后，γ-氨基丁酸水平在出生后的前两周内保持较高，然后在第三周达到与成年值相当的平台期。谷氨酸和天冬氨酸水平从出生到年轻成年期逐渐升高，在出生后第3天（P3）和第11天（P11）出现峰值。甘氨酸和牛磺酸在产前阶段浓度相对较低，出生后显著升高约4倍；它们的水平在出生后第一周结束时下降，但此后逐渐升高，直到第三周达到成年值。为了确定小脑皮质中内源性神经递质的产生情况，分析了在P10制备的原代组织型小脑培养物，并将体外递质含量与成年原位值进行比较。培养物中谷氨酸和天冬氨酸水平大致相同；然而，它们的浓度比体内低一半，这表明二者在小脑皮质内部回路兴奋性神经传递中发挥同等重要的作用，并且在成熟小脑中，约50%的兴奋性突触输入来自传入的攀缘纤维和苔藓纤维。体外γ-氨基丁酸和甘氨酸含量与体内水平相当，而牛磺酸浓度在体外比体内低约5倍。这些发现表明，大多数γ-氨基丁酸和甘氨酸递质是内在产生的，而小脑中高比例的牛磺酸来自小脑外传入纤维。本研究提供了发育中小鼠小脑氨基酸神经递质水平变化的数据，以及与源自外在传入纤维的神经递质含量相比，内在神经元产生的神经递质含量的相对比例。
