Jacob J M, Croes S A
Department of Anatomical Sciences, University of Oklahoma Health Sciences Center, 940 S.L. Young Boulevard, Oklahoma City, Oklahoma, 73104, USA.
Exp Neurol. 1998 Aug;152(2):231-7. doi: 10.1006/exnr.1998.6850.
The conditioning lesion paradigm has proven to be a very useful model in which to examine the mechanisms of axonal outgrowth after injury. In the present study, we have used the conditioning lesion model to examine the ability of motor axons from mature (6-8 months) and old (22-24 months) Fischer 344 rats to form new axonal sprouts. We show that after a single lesion (sham-conditioned axons followed by a testing lesion), axonal outgrowth rates are slower at earlier vs longer postlesion times in mature rats: between 4 and 8 days postlesion, outgrowth rates are 2.4 +/- 0.4 mm/day, whereas between 8 and 11 days postlesion outgrowth rates are 4.6 +/- 0.7 mm/day. After a single lesion in the old rat, at early postlesion times, the axonal outgrowth rate is 1.9 +/- 0.4 mm/day but with increasing time after injury, outgrowth rates slow down to 1.1 +/- 0.8 mm/day. In conditioned motor axons from mature rats, outgrowth rates increase from 3.1 +/- 0.4 mm/day at early postlesion times to 5.2 +/- 0.6 mm/day at longer postlesion times. An even more dramatic increase in outgrowth rate is seen in conditioned axons from old rats: 2.4 +/- 0. 4 mm/day at early postlesion times to 6.3 +/- 1.0 mm/day at later times after lesion. There is no change in the initial delay before sprouting under any condition. These data support the hypothesis that axons from old animals can be stimulated to repair themselves at rates comparable to those seen in younger animals and suggest that there may be an absolute maximum outgrowth rate attainable by newly forming axon sprouts.
条件性损伤范式已被证明是一种非常有用的模型，可用于研究损伤后轴突生长的机制。在本研究中，我们使用条件性损伤模型来检测成熟（6 - 8个月）和老年（22 - 24个月）的Fischer 344大鼠运动轴突形成新轴突发芽的能力。我们发现，在单次损伤后（假条件性轴突随后进行测试性损伤），成熟大鼠在损伤后早期与较长时间相比，轴突生长速度较慢：损伤后4至8天，生长速度为2.4±0.4毫米/天，而损伤后8至11天，生长速度为4.6±0.7毫米/天。老年大鼠单次损伤后，在损伤后早期，轴突生长速度为1.9±0.4毫米/天，但随着损伤后时间的增加，生长速度减慢至1.1±0.8毫米/天。在成熟大鼠的条件性运动轴突中，生长速度从损伤后早期的3.1±0.4毫米/天增加到损伤后较长时间的5.2±0.6毫米/天。在老年大鼠的条件性轴突中观察到生长速度有更显著的增加：损伤后早期为2.4±0.4毫米/天，损伤后后期为6.3±1.0毫米/天。在任何条件下，发芽前的初始延迟都没有变化。这些数据支持这样的假设，即老年动物的轴突可以被刺激以与年轻动物相当的速度自我修复，并表明新形成的轴突发芽可能存在一个绝对的最大生长速度。
