The effect of a conditioning lesion on the regeneration rate of peripheral nerve axons containing substance P.
The regeneration rate of peripheral nerve axons containing substance P-like immunoreactivity (SPLI) was measured in rat sciatic nerve by radioimmunoassay of SPLI in nerve segments 2, 4 and 6 days after a test lesion made by briefly crushing the nerve at the hip. The regeneration rate of the fastest growing sensory axons was also measured in the same nerves using the pinch-reflex procedure. Three groups of animals were compared: group S, which received only the single test lesion, had regeneration rates of 3.57 +/- 0.26 (S.E.) mm/day for SPLI-containing axons and 3.53 +/- 0.14 mm/day for the fastest growing sensory axons. Group A/H, which received a conditioning lesion on the tibial nerve at the ankle 7 days prior to the test lesion at the hip, had a regeneration rate for SPLI-containing axons which was not significantly different from group S, of 3.35 +/- 0.17 mm/day. However, the regeneration rate for the sensory axons was significantly increased to 4.60 +/- 0.23 mm/day. Group H/H, which received both conditioning and test lesions at the hip, once again separated by 7 days, showed a significant increase in regeneration rate of SPLI-containing axons to 5.50 +/- 0.33 mm/day and a further increase over group A/H in the regeneration rate of sensory axons to 6.70 +/- 0.25 mm/day. We conclude that the small-diameter, unmyelinated axons containing SPLI in peripheral nerve normally regenerate at the same rate as the fastest growing sensory axons.(ABSTRACT TRUNCATED AT 250 WORDS)
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Bisby
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P
Keen
D000818:Animals; D001369:Axons / Q000502:physiology*; D003216:Conditioning, Operant / Q000502:physiology; D008297:Male; D009409:Nerve Crush; D009416:Nerve Regeneration; D010525:Peripheral Nerves / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012584:Sciatic Nerve / Q000293:injuries; D013373:Substance P / Q000032:analysis*
D013373:Substance P