Yezierski R P, Schwartz R H
J Neurophysiol. 1986 Jan;55(1):76-96. doi: 10.1152/jn.1986.55.1.76.
Recordings were made from 90 identified spinomesencephalic tract (SMT) cells in the lumbosacral spinal cord of cats anesthetized with alpha-chloralose and pentobarbital sodium. Recording sites were located in laminae I-VIII. Antidromic stimulation sites were located in different regions of the rostral and caudal midbrain including the periaqueductal gray, midbrain reticular formation, and the deep layers of the superior colliculus. Twelve SMT cells were antidromically activated from more than one midbrain level or from sites in the medial thalamus. The mean conduction velocity for the population of cells sampled was 45.2 +/- 21.4 m/s. Cells were categorized based on their responses to graded intensities of mechanical stimuli and the location of excitatory and/or inhibitory receptive fields. Four major categories of cells were encountered: wide dynamic range (WDR); high threshold (HT); deep/tap; and nonresponsive. WDR and HT cells had excitatory and/or inhibitory receptive fields restricted to the ipsilateral hindlimb or extending to other parts of the body including the tail, forelimbs, and face. Some cells had long afterdischarges following noxious stimulation, whereas others had high rates of background activity that was depressed by nonnoxious and noxious stimuli. Deep/tap cells received convergent input from muscle, joint, or visceral primary afferent fibers. The placement of mechanical lesions at different rostrocaudal levels of the cervical spinal cord provided information related to the spinal trajectory of SMT axons. Six axons were located contralateral to the recording electrode in the ventrolateral/medial or lateral funiculi while two were located in the ventrolateral funiculus of the ipsilateral spinal cord. Stimulation at sites used to antidromically activate SMT cells resulted in the inhibition of background and evoked responses for 22 of 25 cells tested. Inhibitory effects were observed on responses evoked by low/high intensity cutaneous stimuli and by the activation of joint or muscle primary afferent fibers. Based on the response and receptive-field properties of SMT cells it is suggested that the SMT may have an important role in somatosensory mechanisms, particularly those related to nociception.
在使用α-氯醛糖和戊巴比妥钠麻醉的猫的腰骶脊髓中，对90个已识别的脊髓中脑束（SMT）细胞进行了记录。记录位点位于I - VIII层。逆向刺激位点位于中脑头端和尾端的不同区域，包括导水管周围灰质、中脑网状结构和上丘深层。12个SMT细胞可从不止一个中脑水平或内侧丘脑的位点被逆向激活。所采样细胞群体的平均传导速度为45.2±21.4米/秒。根据细胞对不同强度机械刺激的反应以及兴奋性和/或抑制性感受野的位置对细胞进行分类。遇到了四类主要细胞：广动力范围（WDR）；高阈值（HT）；深部/轻叩；和无反应型。WDR和HT细胞的兴奋性和/或抑制性感受野局限于同侧后肢，或延伸至身体的其他部位，包括尾巴、前肢和面部。一些细胞在有害刺激后有长时间的后放电，而另一些细胞有高背景活动率，这种活动会被无害和有害刺激所抑制。深部/轻叩细胞接受来自肌肉、关节或内脏初级传入纤维的汇聚输入。在颈髓不同头尾水平放置机械损伤提供了与SMT轴突脊髓走行相关的信息。6条轴突位于记录电极对侧的腹外侧/内侧或外侧索，而2条位于同侧脊髓的腹外侧索。在用于逆向激活SMT细胞的位点进行刺激，导致25个受试细胞中的22个细胞的背景和诱发反应受到抑制。在低/高强度皮肤刺激以及关节或肌肉初级传入纤维激活所诱发的反应上均观察到抑制作用。根据SMT细胞的反应和感受野特性，提示SMT可能在躯体感觉机制中起重要作用，尤其是与伤害感受相关的机制。
