Departamento de Biología Celular y Ecología, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain.
J Comp Neurol. 2013 Feb 15;521(3):522-57. doi: 10.1002/cne.23189.
Glutamate is the major excitatory neurotransmitter in vertebrates, and glutamatergic cells probably represent a majority of neurons in the brain. Physiological studies have demonstrated a wide presence of excitatory (glutamatergic) neurons in lampreys. The present in situ hybridization study with probes for the lamprey vesicular glutamate transporter (VGLUT) provides an anatomical basis for the general distribution and precise localization of glutamatergic neurons in the sea lamprey brainstem. Most glutamatergic neurons were found within the periventricular gray layer throughout the brainstem, with the following regions being of particular interest: the optic tectum, torus semicircularis, isthmus, dorsal and medial nuclei of the octavolateral area, dorsal column nucleus, solitary tract nucleus, motoneurons, and reticular formation. The reticular population revealed a high degree of cellular heterogeneity including small, medium-sized, large, and giant glutamatergic neurons. We also combined glutamate immunohistochemistry with neuronal tract-tracing methods or γ-aminobutyric acid (GABA) immunohistochemistry to better characterize the glutamatergic populations. Injection of Neurobiotin into the spinal cord revealed that retrogradely labeled small and medium-sized cells of some reticulospinal-projecting groups were often glutamate-immunoreactive, mostly in the hindbrain. In contrast, the large and giant glutamatergic reticulospinal perikarya mostly lacked glutamate immunoreactivity. These results indicate that glutamate immunoreactivity did not reveal the entire set of glutamatergic populations. Some spinal-projecting octaval populations lacked both VGLUT and glutamate. As regards GABA and glutamate, their distribution was largely complementary, but colocalization of glutamate and GABA was observed in some small neurons, suggesting that glutamate immunohistochemistry might also detect non-glutamatergic cells or neurons that co-release both GABA and glutamate.
谷氨酸是脊椎动物中主要的兴奋性神经递质，谷氨酸能细胞可能代表了大脑中大多数神经元。生理研究表明，七鳃鳗中存在广泛的兴奋性（谷氨酸能）神经元。本研究用针对七鳃鳗囊泡谷氨酸转运体（VGLUT）的探针进行原位杂交，为海七鳃鳗脑干中谷氨酸能神经元的一般分布和精确定位提供了解剖学基础。大多数谷氨酸能神经元位于整个脑干的室周灰质层内，以下区域特别值得关注：视顶盖、半规管、脑桥、八脑室背核、内侧核、背柱核、孤束核、运动神经元和网状结构。网状结构群体显示出高度的细胞异质性，包括小、中、大、巨大谷氨酸能神经元。我们还将谷氨酸免疫组织化学与神经元束追踪方法或γ-氨基丁酸（GABA）免疫组织化学相结合，以更好地描述谷氨酸能群体。将 Neurobiotin 注入脊髓后，发现一些投射到脊髓的网状脊髓神经元的逆行标记的小和中型细胞通常对谷氨酸免疫反应阳性，主要在脑桥。相比之下，大型和巨大的谷氨酸能网状脊髓神经元体大多缺乏谷氨酸免疫反应性。这些结果表明，谷氨酸免疫反应性并未揭示整个谷氨酸能群体。一些投射到八脑室的神经元群体既缺乏 VGLUT 也缺乏谷氨酸。至于 GABA 和谷氨酸，它们的分布在很大程度上是互补的，但在一些小神经元中观察到谷氨酸和 GABA 的共定位，表明谷氨酸免疫组织化学可能也能检测到非谷氨酸能细胞或同时释放 GABA 和谷氨酸的神经元。
