Dado R J, Giesler G J
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
J Neurosci. 1990 Aug;10(8):2672-86. doi: 10.1523/JNEUROSCI.10-08-02672.1990.
In cats, spinal and medullary input to the thalamic nucleus submedius (Sm) arises almost exclusively from neurons in the marginal zone. As a result, it has been proposed that Sm may be specifically involved in nociception. In the present study, we determined the locations of neurons in the spinal cord and caudal medulla that project to Sm in rats. Iontophoretic injections of Fluoro-Gold or pressure injections of Fast blue were made into Sm. In each of the 6 rats that received small injections of Fluoro-Gold into Sm, only a small number (mean = 90) of retrogradely labeled neurons were found throughout the 18 segments of the spinal cord examined. Surprisingly, almost no labeled neurons (less than 1%) were counted in the marginal zone of the spinal cord. The majority were located in the deep dorsal horn and intermediate zone/ventral horn. In contrast, many neurons were labeled in the marginal zone of nucleus caudalis. Injections of Fluoro-Gold into any of a number of nuclei near Sm also labeled only a small number of neurons in the spinal cord and almost no neurons in the marginal zone. Using identical injection parameters, we injected Fluoro-Gold into the ventrobasal complex or posterior thalamic group. Hundreds of neurons in the spinal cord, including many in the marginal zone, were labeled following these injections. These results indicate that the techniques used to inject Fluoro-Gold into Sm were capable of labeling many projection neurons, including those in the marginal zone. Larger pressure injections of Fast blue were also made into Sm of 3 rats. The distribution of labeled neurons in nucleus caudalis and the spinal cord was similar to that following iontophoretic injections of Fluoro-Gold. Again, few marginal zone neurons were labeled in the spinal cord in any of these rats. Therefore, our results indicate that few spinothalamic tract neurons appear to project to Sm or any of several adjacent nuclei, and virtually no marginal zone neurons in the spinal cord project to these areas.
在猫中，丘脑中间核（Sm）的脊髓和延髓输入几乎完全来自边缘区的神经元。因此，有人提出Sm可能特别参与痛觉感受。在本研究中，我们确定了大鼠脊髓和延髓尾段中投射到Sm的神经元的位置。将荧光金离子导入或快蓝压力注射到Sm中。在6只接受向Sm小剂量注射荧光金的大鼠中，在所检查的脊髓18个节段中仅发现少量（平均 = 90个）逆行标记的神经元。令人惊讶的是，在脊髓边缘区几乎没有计数到标记的神经元（不到1%）。大多数位于背角深层和中间带/腹角。相比之下，尾核边缘区有许多神经元被标记。将荧光金注射到Sm附近的多个核中的任何一个，也仅标记了脊髓中的少量神经元，而边缘区几乎没有神经元被标记。使用相同的注射参数，我们将荧光金注射到腹侧基底复合体或丘脑后组。这些注射后，脊髓中有数百个神经元被标记，包括边缘区的许多神经元。这些结果表明，用于将荧光金注射到Sm的技术能够标记许多投射神经元，包括边缘区的那些神经元。还对3只大鼠的Sm进行了更大剂量的快蓝压力注射。尾核和脊髓中标记神经元的分布与荧光金离子导入注射后的分布相似。同样，在这些大鼠中的任何一只中，脊髓边缘区几乎没有神经元被标记。因此，我们的结果表明，几乎没有脊髓丘脑束神经元似乎投射到Sm或几个相邻核中的任何一个，并且脊髓中几乎没有边缘区神经元投射到这些区域。
