Miranda-Contreras L, Ramírez-Martens L M, Benítez-Diaz P R, Peña-Contreras Z C, Mendoza-Briceño R V, Palacios-Prü E L
Electron Microscopy Center, University of Los Andes, Mérida, Venezuela.
Int J Dev Neurosci. 2000 Feb;18(1):83-91. doi: 10.1016/s0736-5748(99)00075-1.
The developmental changes in the levels of amino acid neurotransmitters were analyzed by high pressure liquid chromatography during mouse olfactory bulb neurogenesis, from embryonic day (E)13 until the young adult age, between postnatal days (P)30 and P40. During the embryonic period, high levels of glutamate, aspartate and GABA were observed, with the values of GABA about 2-fold higher than those of glutamate and aspartate. At P0, the production of these neurotransmitters experienced birth stress as shown by a significant 2-fold reduction in their levels. During the first two postnatal weeks, a progressive increase in the glutamate content was detected diminishing slightly in the adult stage. The aspartate concentrations showed a maximal value at P3 and then decreased gradually until the second postnatal week; in the young adult age, its concentration was comparable with that of glutamate. The postnatal GABA contents increased progressively from birth to maturity, showing maximal levels at P3, P11 and in the adult. Throughout the studied developmental period, the concentration of glycine remained relatively low. With regard to taurine, very low concentrations were detected during the prenatal period but after birth, the taurine content gradually increased with age, and in the adult animal, its concentration was comparable with those of GABA and glutamate. Our data demonstrate the predominance of GABA and glutamate during olfactory bulb synaptogenesis, however, in the adult animal, both glutamate and aspartate exert the same influence in the excitatory synaptic transmission; in the adult inhibitory synaptic transmission, taurine appears to play an important neuromodulatory or neurotransmitter role as that of GABA. To determine the intrinsic neurotransmitter production, primary histotypic olfactory bulb cultures were prepared from mice at P10. The comparative analysis of in vitro neurotransmitter contents with those in in situ adult animal showed higher levels of endogenously produced glutamate, glycine and GABA in the olfactory bulb than the extrinsic ones coming from olfactory nerve axons and higher olfactory brain centers. On the other hand, most of aspartate and taurine neurotransmitters apparently come from extrinsically located neurons.
在小鼠嗅球神经发生过程中，从胚胎期（E）13直到成年早期（出生后第30天至第40天），通过高压液相色谱法分析了氨基酸神经递质水平的发育变化。在胚胎期，观察到谷氨酸、天冬氨酸和GABA水平较高，GABA的值比谷氨酸和天冬氨酸高约2倍。在出生后第0天，这些神经递质的产生经历了出生应激，其水平显著降低了2倍。在出生后的前两周，检测到谷氨酸含量逐渐增加，在成年期略有下降。天冬氨酸浓度在出生后第3天达到最大值，然后逐渐下降直到出生后第二周；在成年早期，其浓度与谷氨酸相当。出生后GABA含量从出生到成熟逐渐增加，在出生后第3天、第11天和成年期达到最高水平。在整个研究的发育期间，甘氨酸浓度相对较低。关于牛磺酸，在产前阶段检测到的浓度非常低，但出生后，牛磺酸含量随年龄逐渐增加，在成年动物中，其浓度与GABA和谷氨酸相当。我们的数据表明，在嗅球突触形成过程中GABA和谷氨酸占主导地位，然而，在成年动物中，谷氨酸和天冬氨酸在兴奋性突触传递中发挥相同的作用；在成年抑制性突触传递中，牛磺酸似乎发挥着与GABA相同重要的神经调节或神经递质作用。为了确定内在神经递质的产生，从出生后第10天的小鼠制备了原代组织型嗅球培养物。体外神经递质含量与成年动物体内神经递质含量的比较分析表明，嗅球中内源性产生的谷氨酸、甘氨酸和GABA水平高于来自嗅神经轴突和高级嗅脑中枢的外源性神经递质水平。另一方面，大多数天冬氨酸和牛磺酸神经递质显然来自位于外部的神经元。
