Blanks R H, Giolli R A, Pham S V
Exp Brain Res. 1982;48(2):228-37. doi: 10.1007/BF00237218.
The projections of the medial terminal nucleus (MTN) of the accessory optic system (AOS) upon pretectal nuclei have been studied in pigmented rats by means of (i) the anterograde transport of 3H-leucine with the use of light autoradiography and (ii) the retrograde transport of horseradish peroxidase (HRP). Injections of 3H-leucine largely restricted to the MTN and minimally involving adjacent ventral midbrain structures, produced heavy terminal axonal labeling within the ipsilateral nucleus of the optic tract (NOT) and the dorsal terminal nucleus (DTN) of the AOS. Terminal labeling was observed in all superficial portions of the NOT, except for a small ventromedial segment in the rostral two thirds and a larger medial segment in the caudal one third of this nucleus. Thus the MTN-NOT projections we describe entirely overlap the retinal-NOT projection and partially overlap the visual cortical-NOT, as reported by others. Within the DTN, the dense terminal fields covered the entire nucleus. After postinjection survival times of 3-7 days, the pattern of axonal labeling showed that the MTN-NOT projection consisted of three bundles: (i) a superficial mesencephalic bundle coursing within the superior fasciculus, posterior fibers of the AOS which enters the caudal portions of the NOT and the DTN; (ii) a deep mesencephalic bundle that traversed the midbrain tegmentum dorsolaterally, also reaching the caudal one-half of the NOT and all of the DTN; and (iii) a mesodiencephalic bundle that passed first laterally through midbrain tegmentum and then dorsally through lateral thalamus to enter the rostral one-half of the NOT. Pretectal injections of HRP that invade the NOT and DTN produced retrograde labeling of most (ca. 75%) of the neurons of the ipsilateral MTN, without labeling the adjacent substantia nigra or ventral tegmental area. This finding confirms our autoradiographic data by showing that the MTN provides the major, ventral tegmental projection to the NOT and DTN. The present finding of a MTN-NOT projection, combined with available anatomical and physiological data, suggests that the MTN may play a more significant role in visual-vestibular aspects of oculomotor control than formerly thought.
利用（i）3H-亮氨酸的顺行运输结合光镜放射自显影技术以及（ii）辣根过氧化物酶（HRP）的逆行运输技术，在有色大鼠中研究了辅助视系统（AOS）的内侧终核（MTN）在前顶盖核上的投射。将3H-亮氨酸注射主要局限于MTN且极少累及相邻的腹侧中脑结构，结果在同侧视束核（NOT）和AOS的背侧终核（DTN）内产生了大量的终末轴突标记。在NOT的所有浅表部分均观察到终末标记，但在该核前三分之二的一个小的腹内侧段以及后三分之一的一个较大的内侧段除外。因此，我们所描述的MTN-NOT投射完全与视网膜-NOT投射重叠，部分与视觉皮层-NOT投射重叠，正如其他人所报道的那样。在DTN内，密集的终末野覆盖了整个核。注射后存活3 - 7天，轴突标记模式显示MTN-NOT投射由三束组成：（i）一束浅表中脑束，在上丘束内走行，是AOS的后纤维，进入NOT和DTN的尾部；（ii）一束深中脑束，从背外侧穿过中脑被盖，也到达NOT的后一半和整个DTN；（iii）一束中脑间脑束，首先向外侧穿过中脑被盖，然后背侧穿过外侧丘脑进入NOT的前一半。在前顶盖注射HRP，其侵入NOT和DTN，结果同侧MTN的大多数（约75%）神经元出现逆行标记，而相邻的黑质或腹侧被盖区未被标记。这一发现通过表明MTN向NOT和DTN提供主要的腹侧被盖投射，证实了我们的放射自显影数据。目前发现的MTN-NOT投射，结合现有的解剖学和生理学数据，表明MTN在眼球运动控制的视觉-前庭方面可能比以前认为的发挥更重要的作用。
