Sawyer S F, Young S J, Groves P M
Department of Neuroscience, School of Medicine, University of California, San Diego, La Jolla 92093.
J Comp Neurol. 1989 Aug 1;286(1):1-27. doi: 10.1002/cne.902860102.
A Golgi study of neurons in the ventroanterior-ventrolateral complex (VAL) and ventromedial (VM) nucleus in the dorsal thalamus of rats was performed. To facilitate the delineation of subdivisions of these nuclei, some animals received injections of horseradish peroxidase (HRP) into the afferent and efferent fields of VAL and VM, and alternate sections were processed for the histochemical detection of HRP. As an adjunct to subjective observations, a multivariate statistical analysis of morphometric variables was performed to provide an objective assessment of neuronal morphology. All Golgi-stained neurons in VAL and VM were tentatively identified as projection neurons; no cells with morphological features commonly ascribed to thalamic interneurons were impregnated. Four classes of morphologically distinct neurons were identified in VAL. Type 1 neurons, the most commonly impregnated cell, were found throughout the extent of VAL and resembled "tufted" or "multipolar bush" neurons described previously in many thalamic nuclei. The remaining three neuronal types differed in a number of morphometric parameters and were differentially distributed throughout VAL. Type 2 neurons, distinguished in part by dendritic spine morphology and elongated bipolar dendritic fields, were found only in the rostral sector of the dorsal division of VAL (VALD). Type 3 neurons, characterized by a large and evenly distributed dendritic field, were situated in rostral VAL (all subdivisions). Type 4 neurons had small soma and dendritic dimensions and were located in the ventromedial aspect of the ventral division of VAL (VALV) adjacent to VM. In contrast, the vast majority of neurons in VM were considered to be a single morphological class (similar in form to type 4 neurons in VAL), although a rarely impregnated second type of neuron was also observed. The apparent scarcity of interneurons in VAL and VM is consistent with previous evidence that the synaptic organization of motor thalamus in the rat is markedly different from that of higher-order mammals. Speculation about the functional attributes of the neuronal types in VAL and VM is necessarily restricted to considerations of afferent and efferent relations, since "motor modality" functions of neurons in these nuclei have yet to be elucidated.
对大鼠背侧丘脑腹前 - 腹外侧复合体（VAL）和腹内侧（VM）核中的神经元进行了高尔基染色研究。为便于描绘这些核的亚区，一些动物在VAL和VM的传入和传出区域注射了辣根过氧化物酶（HRP），并对交替切片进行HRP的组织化学检测。作为主观观察的辅助手段，对形态计量学变量进行了多变量统计分析，以客观评估神经元形态。VAL和VM中所有经高尔基染色的神经元初步鉴定为投射神经元；未观察到具有通常归因于丘脑中间神经元形态特征的细胞被浸染。在VAL中鉴定出四类形态上不同的神经元。1型神经元是最常被浸染的细胞类型，在VAL的整个区域均有发现，类似于先前在许多丘脑核中描述的“簇状”或“多极灌木状”神经元。其余三种神经元类型在多个形态计量参数上有所不同，且在VAL中分布各异。2型神经元部分通过树突棘形态和细长的双极树突野来区分，仅在VAL背侧部（VALD）的 Rostral 区发现。3型神经元的特征是具有大且分布均匀的树突野，位于 Rostral VAL（所有亚区）。4型神经元的胞体和树突尺寸较小，位于VAL腹侧部（VALV）与VM相邻的腹内侧。相比之下，VM中的绝大多数神经元被认为属于单一形态类型（形态与VAL中的4型神经元相似），尽管也观察到一种很少被浸染的第二种神经元类型。VAL和VM中中间神经元明显稀少，这与先前的证据一致——大鼠运动丘脑的突触组织与高阶哺乳动物的明显不同。由于这些核中神经元的“运动模式”功能尚未阐明，因此对VAL和VM中神经元类型功能属性的推测必然仅限于对传入和传出关系的考虑。
