Changes in mechano-receptive properties of Abeta-fiber induced by antidromical electrical stimulation of the cutaneous nerve from adjacent spinal segment / 生理学报

ABSTRACT

The purpose of the present study was to observe whether primary afferent Abeta-fiber is involved in the information transmission between peripheral terminals of adjacent dermatomes. The dorsal cutaneous nerve branches of spinal nerves from T(8) to T(12) segments were cut proximally. One peripheral stump end of the cut nerves was dissected into a few filaments for the examination of mechanoreceptive properties of single Abeta-fibers and their discharges were observed while the other end was stimulated antidromically. Fifty Abeta-units were recorded in forty-two intact rats. After an electrical stimulation (0.45 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) Abeta-fibers extended. The mean area of receptive fields of all examined units enlarged from 8.94+/-6.51 mm(2) to 20.34+/-16.17 mm(2) (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 mechanoreceptive 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 in 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 1.52+/-0.46 min. The changes in mechanoreceptive 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 the changes in mechanoreceptive properties following an antidromical electrical stimulation of adjacent spinal segment. These results suggest that low-threshold mechanoreceptive Abeta-fibers are affected by antidromical electrical stimulation of the cutaneous nerve from an adjacent spinal segment, indicating that information transmission occurs between the two endings of peripheral afferent nerves from adjacent spinal segments without any involvement of the central nervous system, and that Abeta-fibers are involved in the process of information transmission between peripheral terminals from adjacent spinal segments.