Zhang X, Kostarczyk E, Giesler G J
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455, USA.
J Neurosci. 1995 Dec;15(12):8393-407. doi: 10.1523/JNEUROSCI.15-12-08393.1995.
Spinohypothalamic tract (SHT) cells are spinal cord neurons with axons that project directly to or through the contralateral hypothalamus. Frequently, SHT axons decussate in the posterior optic chiasm, turn posteriorly and descend to unknown locations in the ipsilateral brain. We attempted to determine the course and the termination of these descending axons. Sixty neurons in the cervical enlargement of rats were antidromically activated initially from the contralateral hypothalamus and then from multiple anterior-posterior levels in the ipsilateral brain. Fifty-three (88%) were backfired with low currents at increased latencies from the ipsilateral brain. The axons of 35 neurons were surrounded with electrode penetrations from which high currents could not activate the neuron antidromically, suggesting the examined axons terminated in the surrounded areas. Seven SHT axons that were surrounded (20%) appeared to terminate in the contralateral hypothalamus, 5 (14%) in the ipsilateral hypothalamus, and 9 (26%) in the ipsilateral thalamus. Fourteen SHT axons (40%) ended in the ipsilateral midbrain mainly in the superior colliculus, cuneiform nucleus or nucleus brachium inferior colliculus. An additional 11 axons were followed even further posteriorly into the ventral pons or rostral medulla. Each of the 26 neurons that could be physiologically classified responded either preferentially or specifically to noxious mechanical stimuli. These results indicate that SHT axons course through a surprisingly long and complex path. After decussating in the hypothalamus, the axons of many SHT neurons descend into the ipsilateral posterior thalamus, midbrain, pons, or even rostral medulla. These axons may provide nociceptive information to a variety of nuclei throughout the diencephalon and brainstem bilaterally.
脊髓丘脑束（SHT）细胞是脊髓神经元，其轴突直接投射至对侧下丘脑或经对侧下丘脑投射。通常，SHT轴突在视交叉后交叉，向后转向并下行至同侧脑内未知位置。我们试图确定这些下行轴突的行径和终末部位。最初从对侧下丘脑，然后从同侧脑内多个前后水平逆向激活大鼠颈膨大处的60个神经元。53个（88%）神经元在同侧脑内以较低电流、延长的潜伏期被逆向激活。35个神经元的轴突被电极穿刺包围，高电流无法从这些穿刺部位逆向激活神经元，提示被检测的轴突在包围区域终末。7个被包围的SHT轴突（20%）似乎终末于对侧下丘脑，5个（14%）终末于同侧下丘脑，9个（26%）终末于同侧丘脑。14个SHT轴突（40%）终末于同侧中脑，主要位于上丘、楔形核或下丘臂核。另外11个轴突被进一步追踪至更靠后的腹侧脑桥或延髓头端。26个可进行生理学分类的神经元中，每个神经元对有害机械刺激均有优先或特异性反应。这些结果表明，SHT轴突行径通过一条惊人的漫长而复杂的路径。在丘脑交叉后，许多SHT神经元的轴突下行至同侧丘脑后部、中脑、脑桥，甚至延髓头端。这些轴突可能双侧地向间脑和脑干的多种核团提供伤害性信息。
