Lin R C, Nicolelis M A, Chapin J K
Department of Neurobiology and Anatomy, Allegheny University of Health Sciences, Philadelphia, PA 19129, USA.
Neuroscience. 1997 Dec;81(3):641-51. doi: 10.1016/s0306-4522(97)00094-8.
The topographic and laminar organizations of the projection system from the zona incerta to the neocortex were studied by using both retrograde and anterograde methods in the rat. Injections of retrograde fluorescent tracers into different cortical areas revealed that the incertocortical projection neurons have a rough topographic organization with respect to their cortical targets. Furthermore, the incertocortical projecting neurons were found mainly in the dorsal and rostral subdivisions of the zona incerta, and none were found in the ventral subdivision. In cases which included three different fluorescent tracers injected into the frontal, the parietal and the occipital cortices, retrogradely single-labelled cells were found intermingled within the dorsal zona incerta. Very few double-labelled cells were noted, and triple-labelled cells were absent. Injections of anterograde tracers into the dorsal zona incerta demonstrate that labelled fibres traverse the striatum and terminate most densely in the outer half of layer I of the neocortex. The density of incertocortical terminals was greatest in the somatosensory cortex, while the innervation of visual cortical areas was sparse. Very fine and sparse bouton-like swellings of labelled incertocortical fibres were found running parallel along the pial surface. Since it has recently been shown that the incertocortical projections derive from GABAergic neurons, the present results suggest that the diffuse and roughly topographic projection from the zona incerta to the cerebral cortex may play an inhibitory role in widespread areas of cerebral cortex. This inhibitory action may preferentially target the distal dendrites of cortical neurons, since the majority of incertocortical terminals were found in the outer part of layer I of the neocortex.
运用逆行和顺行示踪法，在大鼠上研究了从未定带到新皮层投射系统的局部定位和分层组织。向不同皮层区域注射逆行荧光示踪剂，结果显示未定带-皮层投射神经元相对于其皮层靶点具有大致的局部定位组织。此外，未定带-皮层投射神经元主要位于未定带的背侧和吻侧亚区，腹侧亚区未发现。在向额叶、顶叶和枕叶皮层注射三种不同荧光示踪剂的实验中，在背侧未定带内发现逆行单标记细胞相互混杂。双标记细胞很少见，未见三标记细胞。向背侧未定带注射顺行示踪剂表明，标记纤维穿过纹状体，最密集地终止于新皮层第I层的外半层。未定带-皮层终末密度在躯体感觉皮层最大，而视觉皮层区域的神经支配稀疏。在软膜表面发现标记的未定带-皮层纤维有非常细且稀疏的纽扣样膨体平行排列。由于最近研究表明未定带-皮层投射源自γ-氨基丁酸能神经元，目前的结果提示从未定带到大脑皮层的弥散且大致的局部定位投射可能在大脑皮层的广泛区域发挥抑制作用。这种抑制作用可能优先作用于皮层神经元的远端树突，因为大多数未定带-皮层终末位于新皮层第I层的外部。
