McDonagh J C, Gorman R B, Gilliam E E, Hornby T G, Reinking R M, Stuart D G
Department of Physiology, The University of Arizona, College of Medicine, Tucson 85724-5051, USA.
J Comp Neurol. 1998 Nov 2;400(4):544-70. doi: 10.1002/(sici)1096-9861(19981102)400:4<544::aid-cne8>3.0.co;2-a.
The purpose of the present study was to compare, in motoneurons (MNs) vs. interneurons (INs), selected passive, transitional, and active (firing) properties, as recorded in slices of lumbosacral spinal cord (SC) taken from the adult turtle. The cells were provisionally classified on the basis of (1) the presence (in selected INs) or absence (MNs and other INs) of spontaneous discharge, (2) a cluster analysis of selected properties of the nonspontaneously firing cells, (3) a comparison to previous data on turtle MNs and INs, and (4) a qualitative comparison of the results with those reported for other vertebrate species (lamprey, cat). The provisional nomenclature accommodated properties appropriate for solely MNs (Main MN group) vs. nonspontaneously firing INs (Main IN-N) vs. spontaneously firing INs (IN-S) and for neurons with two degrees of intermediacy between the Main MN and the Main IN-N groups (Overlap MN, Overlap MN/IN). Morphological reconstructions of additional cells, which had been injected with biocytin during the electrophysiological tests, were shown to provide clear-cut support for the provisional classification procedure. The values for the measured parameters in the 96 tested cells covered the spectrum reported previously across adult vertebrate species and were robust in measurements made on different SC slices up to 5 days after their removal from the host animal. The interspecies comparisons permitted the predictions that (1) our Main MN and Overlap MN cells would be analogous to two MN types that innervate fast-twitch and slow-twitch skeletomotor muscle fibers, respectively, in the cat, and (2) the MNs in our Overlap MN/IN group probably innervate slow (nontwitch, tonic) muscle fibers whose presence has recently been established in the turtle hindlimb. In summary, the results bring out the utility of the SC slice preparation of the turtle for study of spinal motor mechanisms in adult tetrapod vertebrates, particularly as an adjunct to the in vivo cat, because of the ease with which robust measurements can be made of the active properties of both MNs and INs.
本研究的目的是比较取自成年海龟腰骶部脊髓（SC）切片中的运动神经元（MNs）和中间神经元（INs）的选定被动、过渡和主动（放电）特性。这些细胞根据以下标准进行初步分类：（1）自发放电的存在与否（选定的INs中有，MNs和其他INs中无）；（2）对非自发放电细胞选定特性的聚类分析；（3）与先前关于海龟MNs和INs的数据进行比较；（4）将结果与其他脊椎动物物种（七鳃鳗、猫）报道的结果进行定性比较。临时命名法适用于仅具有MNs特性的细胞（主要MN组）、非自发放电的INs（主要IN-N组）、自发放电的INs（IN-S组）以及在主要MN组和主要IN-N组之间具有两种中间程度的神经元（重叠MN、重叠MN/IN）。在电生理测试期间注射了生物胞素的其他细胞的形态重建显示，为临时分类程序提供了明确的支持。96个测试细胞中测量参数的值涵盖了先前报道的成年脊椎动物物种的范围，并且在从宿主动物取出后长达5天的不同SC切片上进行的测量中是可靠的。种间比较得出以下预测：（1）我们的主要MN细胞和重叠MN细胞分别类似于猫中支配快肌和慢肌骨骼运动肌纤维的两种MN类型；（2）我们的重叠MN/IN组中的MNs可能支配最近在海龟后肢中发现的慢（非抽搐、紧张性）肌纤维。总之，这些结果表明，海龟的SC切片制备对于研究成年四足脊椎动物的脊髓运动机制具有实用性，特别是作为体内猫研究的辅助手段，因为可以轻松地对MNs和INs的活性特性进行可靠测量。
