An experimental study of the origin and the course of the centrifugal fibres to the olfactory bulb in the rat.
An experimental study of the origin and the course of the centrifugal fibres to the olfactory bulb in the rat.
复制标题
大鼠嗅球离心纤维的起源和过程的实验研究。
作者：
J. Price;T. Powell
现在有解剖学证据表明，在所有的感觉系统中，都存在从更中央到更外周水平的纤维，尽管术语“离心”并不总是用于这种“返回”纤维通路。在感觉通路最外围的这种纤维的例子是y-传出纤维和橄榄耳蜗束，两者都传递到受体，而在最中央的水平，现在有电子显微镜证据表明纤维从大脑皮层的感觉区传递回丘脑的相关感觉中继核（Szentagothai，Hamori & Tombol，1966; Jones & Powell，1969）。在过去的二十年里，这些“离心”纤维系统的功能意义的阐明一直是电生理学工作的一个令人兴奋和富有成果的领域（见Granit，1955;马修斯，1964; Whitfield，1967）。Ramon y Cajal（1911）在用高尔基染色法对正常大脑进行的研究中，发现了从外侧嗅束向前进入嗅球的相对粗糙的纤维。他将这些轴突描述为离心的，并将它们与前连合中更细、更深的轴突明确区分开来。虽然卡哈尔不确定离心纤维的来源，但他认为它们来自蝶骨皮质或嗅束。多年来，这些离心纤维的存在不是被忽视就是被否认（参见Allison，1953;绿色，Mancia和von Baumgarten，1962），但现在已在家兔中提供了它们存在的实验解剖学证据（Cragg，1962），老鼠（Powell &科万，1963年; Powell，科万& Raisman，1965年; Heimer，1968年），以及海狸鼠（Girgis & Goldby，1967）;和Powell等人（1965）已经表明这些纤维进入并靠近外侧嗅束。Cragg（1962）和Powell等人（1965）的材料不适合确定离心纤维的起源，但这些作者认为它们起源于嗅结节区域。Heimer（1968）最近声称离心纤维来自广泛的区域，包括梨状皮质，不能被认为是证实的，因为他的病变可能涉及外侧嗅束。由于离心纤维与嗅球的僧帽细胞的中央定向轴突密切相关，嗅球对侧嗅束的电刺激的反应可能部分是由于这些离心纤维的激活以及僧帽细胞轴突的逆向刺激（菲利普斯，Powell & Shepherd，1963）。对于离心纤维的电生理学研究，了解它们的起源部位将是有利的，并且在离心纤维中，
There is now anatomical evidence for the presence of fibres passing from more central to more peripheral levels in all the sensory systems, although the term 'centrifugal' is not always used for such 'returning' fibre pathways. Examples of such fibres at the extreme periphery of the sensory pathways are the y-efferent fibres and the olivo-cochlear bundle, both of which pass out to the receptors, while at the most central level there is now electron microscopic evidence to show that fibres pass back to the relevant sensory relay nuclei of the thalamus from the sensory areas of the cerebral cortex (Szentagothai, Hamori & Tombol,1966; Jones & Powell, 1969). The elucidation of the functional significance of these 'centrifugal' fibre systems has been a stimulating and fruitful field of electrophysiological work during the past two decades (see Granit, 1955; Matthews, 1964; Whitfield, 1967). In his studies of normal brains stained with the Golgi method, Ramon y Cajal (1911) found relatively coarse fibres which pass forwards into the olfactory bulb from the lateral olfactory tract. He described these axons as centrifugal, and clearly distinguished them from the finer, more deeply situated axons of the anterior commissure. Although Cajal was uncertain of the origin of the centrifugal fibres, he suggested that they came from the sphenoidal cortex or the olfactory tract. For many years the presence of these centrifugal fibres was either ignored or denied (see Allison, 1953; Green, Mancia & von Baumgarten, 1962), but experimental anatomical evidence of their presence has now been provided in the rabbit (Cragg, 1962), the rat (Powell & Cowan, 1963; Powell, Cowan & Raisman, 1965; Heimer, 1968), and the coypu (Girgis & Goldby, 1967); and Powell et al. (1965) have shown that these fibres pass in and close to the lateral olfactory tract. The material of Cragg (1962), and of Powell et al. (1965) was not suitable for determining the origin of the centrifugal fibres, but these authors suggested that they arose from the region of the olfactory tubercle. The recent claim of Heimer (1968) that the centrifugal fibres arise from widespread areas, including the pyriform cortex, cannot be considered substantiated as his lesions may have involved the lateral olfactory tract. Because the centrifugal fibres pass in close relation to the centrally directed axons of the mitral cells of the olfactory bulb, the responses in the olfactory bulb to electrical stimulation of the lateral olfactory tract might be due in part to activation of these centrifugal fibres, as well as to antidromic stimulation of the mitral cell axons (Phillips, Powell & Shepherd, 1963). For an electro-physiological study of the centrifugal fibres, it would be advantageous to know their site of origin, and in the