Vierck C J, Greenspan J D, Ritz L A
Department of Physiology, University of North Carolina School of Medicine, Chapel Hill 27514.
J Neurosci. 1990 Jul;10(7):2077-95. doi: 10.1523/JNEUROSCI.10-07-02077.1990.
Macaca nemestrina monkeys received unilateral interruption of the spinothalamic tract, producing contralateral hypalgesia and a bilateral decrease in amplitude of the flexion reflex. These effects on operant escape and reflex responses to electrocutaneous stimulation (ES) were monitored for months to evaluate relationships between the extent of each lesion and the presence or absence of recovery from the early postoperative deficits. Before surgery, the animals were trained to perform an operant response that terminated ES to the lateral calf of either leg. The durations of ES tolerated by each monkey were inversely related to stimulus intensities within the pain sensitivity range of human subjects. The vigor of operant escape responses and the frequency of intertrial pulls of the manipulandum were directly related to stimulus intensity. Following anterolateral chordotomy at an upper thoracic level, these measures revealed a contralateral hypalgesia for each animal. Operant responsivity to stimulation contralateral to the lesion recovered to control levels for 7 animals (group R). Sustained contralateral recovery of operant reactivity was not observed for 8 monkeys (group U). Most of the lesions in groups R and U were similar in extent and location, involving the classical distribution of the spinothalamic tract (in the anterolateral and ventral columns). Thus, recovery was not determined solely by lesion configuration. However, when recovery did occur, it was associated with medially extensive lesions. A subgroup of 3 unrecovered animals received superficial lesions that did not substantially involve the gray matter or the ventral columns. For all animals, reflex magnitudes were initially diminished bilaterally and then increased over months of testing. Reflex recovery was greater for the animals that demonstrated recovery of intentional reactions to nociception (group R). An ipsilateral hyperreflexia became apparent for group R. Contralateral recovery to normal levels was observed for group R but not for group U. The time course of recovery for operant and reflex responses clearly differed, indicating that different processes determined changes in these spinal and supraspinal reactions to nociceptive stimulation.
豚尾猕猴接受了单侧脊髓丘脑束切断术，导致对侧痛觉减退以及双侧屈肌反射幅度降低。对这些动物的操作逃避行为以及对皮肤电刺激（ES）的反射反应进行了数月监测，以评估每个损伤的范围与术后早期缺陷恢复与否之间的关系。手术前，训练动物执行一种操作反应，该反应可终止对任一侧小腿外侧的ES。每只猴子耐受ES的持续时间与人类受试者疼痛敏感范围内的刺激强度呈负相关。操作逃避反应的强度和操作柄的试间拉动频率与刺激强度直接相关。在胸段上部进行前外侧脊髓切断术后，这些指标显示每只动物均出现对侧痛觉减退。7只动物（R组）对损伤对侧刺激的操作反应性恢复到了对照水平。8只猴子（U组）未观察到对侧操作反应性的持续恢复。R组和U组的大多数损伤在范围和位置上相似，涉及脊髓丘脑束的经典分布（在前外侧柱和腹侧柱）。因此，恢复并非仅由损伤形态决定。然而，当恢复确实发生时，它与内侧广泛的损伤有关。3只未恢复的动物亚组接受了浅部损伤，这些损伤基本未累及灰质或腹侧柱。对于所有动物，反射幅度最初双侧降低，然后在数月的测试中增加。对于表现出对伤害性刺激的有意反应恢复的动物（R组），反射恢复程度更大。R组出现了同侧反射亢进。R组观察到对侧恢复到正常水平，而U组未观察到。操作反应和反射反应的恢复时间进程明显不同，表明不同的过程决定了这些脊髓和脊髓上对伤害性刺激反应的变化。
