Sawyer S F, Martone M E, Groves P M
Department of Neuroscience, School of Medicine, University of California, San Diego, La Jolla 92093.
Neuroscience. 1991;42(1):103-24. doi: 10.1016/0306-4522(91)90152-e.
A light and electron microscopic study of GABA-immunoreactive neurons and profiles in the ventroanterior-ventrolateral and ventromedial nuclei of rat dorsal thalamus was conducted using antiserum raised against GABA. Less than 1% of the neurons in these motor-related nuclei exhibited GABA immunoreactivity, confirming previous reports that these nuclei are largely devoid of interneurons. Immunoreactive neurons in the ventral anterior-ventral lateral complex and ventromedial nucleus were bipolar or multipolar in shape, and tended to be smaller than non-immunoreactive neurons. GABA immunoreactivity in the neuropil consisted of labeled axon terminals and myelinated and unmyelinated axons, and was lower in the ventral anterior-ventral lateral complex and ventromedial nucleus than in neighboring thalamic nuclei. The density of neuropil immunolabeling was slightly higher in ventral anterior-ventral lateral complex than in ventromedial nucleus. GABA-immunoreactive axon terminals, collectively termed MP boutons for their medium size and pleomorphic vesicles (and corresponding to "F" profiles of some previous studies of thalamic ultrastructure), formed symmetric synapses and puncta adhaerentia contacts predominantly with large and medium-diameter (i.e. proximal) non-immunoreactive dendrites. Approximately 12 and 18% of boutons in the ventral anterior-ventral lateral complex and ventromedial nucleus, respectively, were GABA-immunopositive. Many of these immunoreactive profiles probably arose from GABAergic neurons in the thalamic reticular nucleus, substantia nigra pars reticulata and entopeduncular nucleus. Two types of non-immunoreactive axon terminals were distinguished based on differences in morphology and synaptic termination sites. Boutons with small ovoid profiles and round vesicles that formed prominent asymmetric synapses onto small-diameter dendrites were observed. Mitochondria were rarely observed within these boutons, which arose from thin unmyelinated axons. These boutons composed approximately 82 and 74% of boutons in the ventral anterior-ventral lateral complex and ventromedial nucleus, respectively, and were considered to arise predominantly from neurons in the cerebral cortex. In contrast, boutons with large terminals that contained round or plemorphic vesicles and formed multiple asymmetric synapses predominantly with large-diameter dendrites were also observed. Puncta adhaerentia contacts were also common. Mitochondria were numerous within large boutons with round vesicles, which arose from myelinated axons. Many of the large boutons were likely to have originated from neurons in the cerebellar nuclei. Approximately 6% of the boutons in the ventral anterior-ventral lateral complex and 8% in ventromedial nucleus were of the large type.(ABSTRACT TRUNCATED AT 400 WORDS)
利用抗γ-氨基丁酸（GABA）抗血清，对大鼠背侧丘脑腹前-腹外侧核及腹内侧核中GABA免疫反应性神经元及神经元轮廓进行了光镜和电镜研究。这些与运动相关的核团中，不到1%的神经元呈现GABA免疫反应性，证实了先前的报道，即这些核团中大部分缺乏中间神经元。腹前-腹外侧复合体和腹内侧核中的免疫反应性神经元呈双极或多极形态，且往往比非免疫反应性神经元小。神经毡中的GABA免疫反应性由标记的轴突终末以及有髓和无髓轴突组成，在腹前-腹外侧复合体和腹内侧核中比在相邻的丘脑核中更低。腹前-腹外侧复合体中神经毡免疫标记的密度略高于腹内侧核。GABA免疫反应性轴突终末，因其中等大小和多形性囊泡而统称为MP终扣（并且对应于一些先前丘脑超微结构研究中的“F”轮廓），主要与大直径和中等直径（即近端）的非免疫反应性树突形成对称突触和黏着斑接触。腹前-腹外侧复合体和腹内侧核中分别约有12%和18%的终扣为GABA免疫阳性。这些免疫反应性轮廓中的许多可能起源于丘脑网状核、黑质网状部和内囊核中的GABA能神经元。根据形态和突触终末部位的差异，区分出两种类型的非免疫反应性轴突终末。观察到具有小卵圆形轮廓和圆形囊泡的终扣在小直径树突上形成明显的不对称突触。这些终扣内很少观察到线粒体，它们起源于细的无髓轴突。这些终扣分别约占腹前-腹外侧复合体和腹内侧核中终扣的82%和74%，被认为主要起源于大脑皮质中的神经元。相比之下，还观察到具有大终末的终扣，其含有圆形或多形性囊泡，主要与大直径树突形成多个不对称突触。黏着斑接触也很常见。在具有圆形囊泡的大终扣内线粒体众多，它们起源于有髓轴突。许多大终扣可能起源于小脑核中的神经元。腹前-腹外侧复合体中约6%的终扣以及腹内侧核中约8%的终扣属于大终扣类型。（摘要截取自400字）
