Received 2002-02-17 Accepted 2002-09-27
This work was supported by the Foundation: National Climbing Project, No.95-19-131
*Corresponding author. Tel: +86-29-2668128; Fax： +86-29-2668668, +86-29-3237910; E-mail qxsun@mail.xjtu.edu.cn
电刺激大鼠皮神经外周端对相邻脊髓节段皮神经内Aβ纤维的机械感受特性的影响
孙启新1*, 赵晏2, 张世红2, 史文春2, 王会生2
1西安交大生命科学与技术学院生物医学工程系, 西安 710049;
2西安交大医学院生理教研室, 西安 710061
摘要: 为观察Aβ类初级传入纤维是否参与相邻脊髓节段外周末梢之间的信息传递及其相关机制, 实验自近中端切断一侧T8~T12脊髓节段背侧皮神经, 将一支被切断的皮神经的外周端分离成数支细束, 以单个Aβ纤维放电为指征, 检测单位的传导速度、适应特性、机械感受阈值、感受野的形状和面积; 在相邻脊髓节段、也与中枢断离的皮神经干上施加逆向电刺激(0.45 mA, 0.1 ms, 20 Hz, 10 s), 以观察该刺激对Aβ纤维的上述机械感受特性的影响。在42只大鼠上共记录了50个Aβ类单位。逆向电刺激相邻节段皮神经后, 60.6％(n=33)的单位感受野增大, 全部单位的感受野平均面积从8.94±6.51 mm2显著增加到20.34±16.17 mm2 (P<0.01)。81.8％ (n=20)的单位感受野形状从点状、圆或与身体长轴垂直的椭圆变成与身体长轴斜行或平行的椭圆。68.0％ (n=50)的单位机械感受阈值下降, 全部单位的平均阈值从2.37±1.24 mN降至2.29±1.24 mN (P<0.05)。上述机械感受特性的改变可持续52.23±9.27至56.93±15.76 min。跨节段电刺激后, 有50.0% (n=50)的单位同时出现放电的增加, 但该增加仅持续1.5 min, 显著短于机械感受特性改变的时程 (P<0.01)。有机械感受特性改变的单位也更容易出现电生理学改变。跨节段电刺激引起的上述机械感受特性和放电的改变均出现于相同的Aβ纤维群中: 都具有较慢的传导速度、较低的机械感受阈值、较大的感受野和慢适应特性。提示, 低阈值机械感受性、少数高阈值感受性Aβ类纤维可被相邻脊髓节段上的皮神经逆向电刺激所激活, 表明在没有中枢神经系统参与的前提下, 两相邻皮节传入神经的外周末梢间产生了信息传递, 即相邻脊髓节段的传入神经末梢之间的信息传递, Aβ类纤维参与了这一过程。
关键词: Aβ类初级传入纤维; 感受野; 机械感受阈值; 相邻皮节神经末梢; 信息传递
中图分类号: Q422, Q429
Changes in mechano-receptive
properties of Aβ-fiber induced by
antidromically electrical stimulation
of the cutaneous nerve from adjacent spinal segment
SUN Qi-Xing1*, ZHAO Yan2, ZHANG Shi-Hong2, SHI Wen-Chun2, WANG Hui-Sheng2
1Department
of Biological Medical Engineering,
2Physiological
Department of Physiology,
Abstract: The purpose of the present study was to observe whether primary afferent Aβ-fiber is involved in the information transmission between peripheral terminals of adjacent dermatomes. The dorsal cutaneous nerve branches of spinal nerves from T8 to T12 segments were cut proximally. One peripheral stump end of the cut nerves was dissected into a few filaments for the examination of mechanoceptive properties of single Aβ-fibers and their discharges were observed while another one was stimulated antidromically. Fifty Aβ-units were recorded in forty-two intact rats. After an electrical stimulation (0.45 mA, 0.1 ms, 20 Hz, for 10 mA, 0.1 ms, 20 Hz, for 10 s) was delivered to the stimulated nerve, the size of the receptive field of 60.6％ (n=33) Aβ-fibers extended. The mean area of receptive fields of all examined units enlarged from 8.94±6.51 mm2 to 20.34±16.17 mm2 (P<0.01) and the shapes of the receptive fields of 81.8％ (n=20) units changed from a dot, round or ellipse with its long axis in parallel with the longitudinal axis of the body to an oblique ellipse with the longitudinal axis of the body. The mechanoceptive threshold of 68.0％ (n=50) units decreased with a reduction in mean threshold from 2.37±1.24 to 2.29±1.24 mN (P<0.05). The duration of these changes of mechano-receptive properties increased from 52.23±9.27 to 56.93±15.76 min. Meanwhile, increasing discharge was found in 50.0% (n=50) units but lasted only for 1.5 min. The changes of mechanoceptive properties appeared simultaneously with discharge changes but had longer duration than that of discharge change (P<0.01). Discharges changes usually appeared in those units with changes of mechanoceptive properties following an antidromical electrical stimulation of adjacent spinal segment. These results suggest that low-threshold mechanoreceptive Aβ-fibers are affected by antidromical electrical stimulation of the cutaneous nerve from an adjacent spinal segment, indicating that information transmission occurs between two endings of peripheral afferent nerves from adjacent spinal segments without any involvement of the central nervous system, and that Aβ-fibers are involved in the process of information transmission between peripheral terminals from adjacent spinal segments.
Key words: primary afferent Aβ-fiber; receptive field; mechanoceptive threshold; information transmission between peripheral terminals from adjacent spinal segments