Holtzman D A, Pfaff D W, Schwartz-Giblin S
Rockefeller University, New York, NY 10021.
Brain Res. 1992 Nov 6;595(1):39-49. doi: 10.1016/0006-8993(92)91450-s.
In the lateral longissimus muscle (LL) of ovariectomized, female rats anesthetized with low surgical doses of urethane (1.0 g/kg), cutaneous reflexes with similar EMG and response patterns could be elicited from CNS-intact rats and from rats 24 h after complete thoracic spinal cord transection. The probability of eliciting a response to contralateral cutaneous nerve stimulation alone is much lower in rats with complete spinal transections compared to CNS-intact rats. For both CNS-intact and spinal-transected rats, responses to ipsilateral cutaneous nerve stimulation had a shorter latency and required significantly less current on average than responses to contralateral stimulation. The respective currents for eliciting threshold responses to ipsi- and contralateral stimulation are less for CNS-intact than spinal-transected rats. For both CNS-intact and spinal-transected rats, responses to bilateral cutaneous nerve stimulation were inconsistent in the same animal from run to run. With the variability of response at this anesthetic level, no consistent effects of progesterone (acute, i.v.) or estrogen (acute, i.v. and pretreatment, s.c.) were observed in spinal-transected rats. Intravenous progesterone reduced early, unilateral responses in CNS-intact rats anesthetized with 1.0 g of urethane/kg. For both CNS-intact and spinal-transected rats, additional anesthesia during EMG recording produced a gradual decline in response magnitude which could be recovered with a modest increase in stimulus intensity. However, spinal-transected rats appear to require less anesthesia to reduce comparable responses. The results suggest that supraspinal input is especially effective for facilitating contralateral cutaneous reflexes in back muscles, whereas it contributes more equally with afferent input and segmental circuitry to the efficacy of ipsilateral cutaneous reflexes.
在接受低剂量手术用氨基甲酸乙酯（1.0 g/kg）麻醉的去卵巢雌性大鼠的外侧最长肌（LL）中，完整中枢神经系统的大鼠以及在完全胸段脊髓横断24小时后的大鼠，均可引出具有相似肌电图和反应模式的皮肤反射。与完整中枢神经系统的大鼠相比，完全脊髓横断的大鼠单独对同侧皮肤神经刺激产生反应的概率要低得多。对于完整中枢神经系统和脊髓横断的大鼠，对同侧皮肤神经刺激的反应潜伏期较短，平均所需电流明显小于对侧刺激的反应。完整中枢神经系统的大鼠引出同侧和对侧刺激阈值反应的相应电流比脊髓横断的大鼠要小。对于完整中枢神经系统和脊髓横断的大鼠，同一只动物每次实验中对双侧皮肤神经刺激的反应都不一致。在这个麻醉水平下，由于反应的变异性，在脊髓横断的大鼠中未观察到孕酮（急性，静脉注射）或雌激素（急性，静脉注射和预处理，皮下注射）的一致作用。静脉注射孕酮可减少用1.0 g氨基甲酸乙酯/kg麻醉的完整中枢神经系统大鼠早期的单侧反应。对于完整中枢神经系统和脊髓横断的大鼠，在肌电图记录期间增加麻醉会使反应幅度逐渐下降，适度增加刺激强度可使其恢复。然而，脊髓横断的大鼠似乎需要较少的麻醉来减少类似反应。结果表明，脊髓上输入对于促进背部肌肉的对侧皮肤反射特别有效，而它与传入输入和节段性回路对同侧皮肤反射功效的贡献更为均等。
