Alstermark B, Pinter M J, Sasaki S, Tantisira B
Department of Physiology, University of Göteborg, Sweden.
Exp Brain Res. 1992;92(2):183-93. doi: 10.1007/BF00227964.
Excitation of dorsal neck motoneurones evoked by electrical stimulation of primary trigeminal afferents in the Gasserian ganglion has been investigated with intracellular recording from alpha-motoneurones in the cat. Single stimulation in the Gasserian ganglion ipsi- and contralateral to the recording side evoked excitatory postsynaptic potentials (EPSPs) in motoneurones innervating the lateral head flexor muscle splenius (SPL) and the head elevator muscles biventer cervicis and complexus (BCC). The gasserian EPSPs were composed of early and late components which gave the EPSPs a hump-like shape. A short train of stimuli, consisting of two to three volleys, evoked temporal facilitation of both the early and late EPSP components. The latencies of the gasserian EPSPs ranged from 1.6 to 3.6 ms in SPL motoneurones and from 1.6 to 5.8 ms among BCC motoneurones. A rather similar latency distribution between 1.6 and 2.4 ms was found for ipsi- and contralateral EPSPs in SPL and BCC motoneurones, which is compatible with a minimal disynaptic linkage between primary trigeminal afferents and neck motoneurones. Systematic transections of the ipsi- and contralateral trigeminal tracts were performed in the brain stem between 3 and 12 mm rostral to the level of obex. The results demonstrate that both the ipsi- and contralateral disynaptic and late gasserian EPSPs can be mediated via trigeminospinal neurones which take their origin in the nucleus trigeminalis spinalis oralis. Transection of the midline showed that the contralateral trigeminospinal neurones cross in the brain stem. Systematic tracking in and around the ipsilateral trigeminal nuclei demonstrated that the axons of ipsilateral trigeminospinal neurones descend just medial to and/or in the medial part of the nucleus. Spinal cord lesions revealed a location of the axons of the ipsilateral trigeminospinal neurones in the lateral and ventral funiculi. Interaction between the ipsi- and contralateral gasserian EPSPs showed complete summation of the disynaptic EPSP component, while the late components were occluded by about 45%. These results show that the disynaptic EPSPs are mediated by separate trigeminospinal neurones from the ipsi- and contralateral side, while about half of the late EPSPs are mediated by common neurones which receive strong bilateral excitation from commissural neurones in the trigeminal nuclei. Spatial facilitation was found in the late gasserian EPSP but not in the disynaptic gasserian EPSP by conditioning stimulation of cortico- and tectofugal fibres. Disynaptic pyramidal and tectal EPSPs, which are mediated by reticulospinal neurones, were facilitated by a single stimulation in the gasserian ganglion at an optimal interval of 2 ms.(ABSTRACT TRUNCATED AT 400 WORDS)
通过对猫的α运动神经元进行细胞内记录，研究了三叉神经节中初级三叉神经传入纤维电刺激诱发的颈背运动神经元兴奋。在记录侧同侧和对侧的三叉神经节进行单次刺激，可在支配头部外侧屈肌夹肌（SPL）以及头部上抬肌二腹肌颈段和头半棘肌（BCC）的运动神经元中诱发兴奋性突触后电位（EPSP）。三叉神经节EPSP由早期和晚期成分组成，使EPSP呈驼峰状。由两到三个波阵面组成的短串刺激可诱发早期和晚期EPSP成分的时间性易化。SPL运动神经元中三叉神经节EPSP的潜伏期为1.6至3.6毫秒，BCC运动神经元中的潜伏期为1.6至5.8毫秒。在SPL和BCC运动神经元中，同侧和对侧EPSP在1.6至2.4毫秒之间有相当相似的潜伏期分布，这与初级三叉神经传入纤维和颈运动神经元之间最少的双突触联系相一致。在脑桥中，于闩平面上方3至12毫米处对同侧和对侧的三叉神经束进行了系统性横切。结果表明，同侧和对侧的双突触及晚期三叉神经节EPSP均可通过起源于三叉神经脊束核吻侧的三叉脊髓神经元介导。中线横切显示，对侧的三叉脊髓神经元在脑桥中交叉。对同侧三叉神经核及其周围进行系统性追踪表明，同侧三叉脊髓神经元的轴突在核的内侧及/或内侧部分的内侧下行。脊髓损伤揭示了同侧三叉脊髓神经元的轴突在外侧索和腹侧索中的位置。同侧和对侧三叉神经节EPSP之间的相互作用显示，双突触EPSP成分完全总和，而晚期成分约被阻断45%。这些结果表明，双突触EPSP由同侧和对侧的不同三叉脊髓神经元介导，而约一半的晚期EPSP由共同神经元介导，这些共同神经元接受来自三叉神经核连合神经元的强烈双侧兴奋。通过对皮质和顶盖传出纤维的条件刺激，在晚期三叉神经节EPSP中发现了空间易化，但在双突触三叉神经节EPSP中未发现。由网状脊髓神经元介导的双突触锥体和顶盖EPSP，在三叉神经节单次刺激时，以2毫秒的最佳间隔出现易化。（摘要截断于400字）
