Senba E, Kaneko T, Mizuno N, Tohyama M
Department of Anatomy II, Osaka University Medical School, Japan.
Brain Res Bull. 1991 Jan;26(1):85-97. doi: 10.1016/0361-9230(91)90193-n.
Immunocytochemistry combined with a fluorescent dye tracer method revealed that somatic, branchial and visceral motoneurons in the brainstem and spinal cord of the rat contain phosphate-activated glutaminase (PAG). An excitatory neurotransmitter glutamate is synthesized mainly through this enzyme. Among these motoneurons, neurons in the dorsal motor nucleus of the vagus nerve (dmnX), autonomic preganglionic neurons in the spinal cord and urethral sphincter motoneurons (DL) were most intensely immunostained. PAG is co-expressed with choline acetyltransferase, calcitonin gene-related peptide or galanin in these neurons. These findings, together with the findings that motor endplates in urethral sphincter muscle contain PAG and PAG-like immunostaining in dmnX motoneurons was decreased after axotomy, suggest that glutamate is a co-transmitter of acetylcholine in motoneurons. Brainstem motoneurons were moderately stained, while somatic motoneurons in the spinal cord other than DL, showed very weak staining for PAG. However, they showed intense PAG-like immunoreactivity at their premature stage, suggesting that glutamate has some effects on the maturation of these neurons. A variety of functional roles of glutamate in motoneurons is discussed.
免疫细胞化学结合荧光染料示踪法显示，大鼠脑干和脊髓中的躯体运动神经元、鳃运动神经元和内脏运动神经元含有磷酸激活谷氨酰胺酶（PAG）。兴奋性神经递质谷氨酸主要通过这种酶合成。在这些运动神经元中，迷走神经背运动核（dmnX）中的神经元、脊髓中的自主神经节前神经元和尿道括约肌运动神经元（DL）的免疫染色最为强烈。在这些神经元中，PAG与胆碱乙酰转移酶、降钙素基因相关肽或甘丙肽共表达。这些发现，以及尿道括约肌肌肉运动终板含有PAG以及轴突切断后dmnX运动神经元中PAG样免疫染色减少的发现，表明谷氨酸是运动神经元中乙酰胆碱的共递质。脑干运动神经元染色中等，而脊髓中除DL外的躯体运动神经元对PAG的染色非常弱。然而，它们在发育早期显示出强烈的PAG样免疫反应性，表明谷氨酸对这些神经元的成熟有一定影响。本文讨论了谷氨酸在运动神经元中的多种功能作用。
