Todd A J, Spike R C, Polgár E
Laboratory of Human Anatomy, Institute of Biomedical and Life Sciences, University of Glasgow, UK.
Neuroscience. 1998 Jul;85(2):459-73. doi: 10.1016/s0306-4522(97)00669-6.
The neurokinin-1 and somatostatin sst2a receptors have both been identified on spinal cord neurons. In this study we have estimated the proportions of neurons in different parts of the spinal cord which express these receptors, by using a monoclonal antibody against a neuronal nuclear protein named NeuN and combining the optical disector method with confocal microscopy. The NeuN antibody was initially tested on over 3200 neurons identified with antisera against a variety of compounds, including neuropeptides, enzymes and receptors, and also on astrocytes and oligodendrocytes. All of the neurons, but none of the glial cells that were examined possessed NeuN-immunoreactivity, which suggests that NeuN is a reliable marker for all spinal cord neurons. We found that approximately 45% of neurons in lamina I, 23-29% of those in laminae IV-VI and 18% in lamina X possessed the neurokinin-1 receptor, while the receptor was present on a smaller proportion of neurons in laminae II and III (6% and 11%, respectively). Thirteen percent of lamina I neurons and 15% of those in lamina II expressed the sst2a receptor. To provide further information about the types of neuron which possess the sst2a receptor, we searched for possible co-existence with the neurokinin-1 receptor as well as with GABA and glycine. sst2a and neurokinin-1 receptors were not co-localized on neurons in laminae I and II. All of the sst2a-immunoreactive neurons examined were also GABA-immunoreactive, and 83.5% were glycine-immunoreactive, indicating that the receptor is located on inhibitory neurons in the superficial dorsal horn. These results demonstrate the proportions of neurons in each region of the spinal cord which can be directly activated by substance P or somatostatin acting through these receptors. Levels of receptors can change in pathological states, and this method could be used to determine whether or not these changes involve alterations in the number of neurons which express receptors. In addition, the method can be used to estimate the sizes of neurochemically-defined populations of spinal cord neurons.
神经激肽-1受体和生长抑素sst2a受体均已在脊髓神经元上被鉴定出来。在本研究中，我们通过使用一种针对名为NeuN的神经元核蛋白的单克隆抗体，并将光学分割法与共聚焦显微镜相结合，估算了脊髓不同部位表达这些受体的神经元比例。NeuN抗体最初在超过3200个用针对多种化合物（包括神经肽、酶和受体）的抗血清鉴定的神经元上进行了测试，同时也在星形胶质细胞和少突胶质细胞上进行了测试。所有被检测的神经元都具有NeuN免疫反应性，但所检测的神经胶质细胞均无此反应，这表明NeuN是所有脊髓神经元的可靠标志物。我们发现，I层中约45%的神经元、IV - VI层中23% - 29%的神经元以及X层中18%的神经元具有神经激肽-1受体，而该受体在II层和III层中神经元的比例较小（分别为6%和11%）。I层中13%的神经元和II层中15%的神经元表达sst2a受体。为了提供关于表达sst2a受体的神经元类型的更多信息，我们寻找了其与神经激肽-1受体以及γ-氨基丁酸（GABA）和甘氨酸可能的共存情况。sst2a和神经激肽-1受体不在I层和II层的神经元上共定位。所有被检测的sst2a免疫反应性神经元也都是GABA免疫反应性的，并且83.5%是甘氨酸免疫反应性的，这表明该受体位于脊髓背角浅层的抑制性神经元上。这些结果表明了脊髓各区域中可被通过这些受体起作用的P物质或生长抑素直接激活的神经元比例。受体水平在病理状态下会发生变化，该方法可用于确定这些变化是否涉及表达受体的神经元数量的改变。此外，该方法可用于估算脊髓神经元神经化学定义群体的大小。
