Central changes in primary afferent fibers following peripheral nerve lesions

• Published in: Neuroscience Vol. 77; no. 4; pp. 1115 - 1122
• Main Authors: Coggeshall, R.E, Lekan, H.A, Doubell, T.P, Allchorne, A, Woolf, C.J
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.1997; Elsevier
• Subjects: Age Factors; Animals; Biological and medical sciences; dorsal root axons; Female; Fundamental and applied biological sciences. Psychology; Male; Nerve Crush; Nerve Fibers - physiology; Neurons, Afferent - physiology; Neurons, Afferent - ultrastructure; nociception; Nociceptors - physiology; primary afferents; Rats; Rats, Sprague-Dawley; Sciatic Nerve - surgery; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Spinal Nerve Roots - cytology; transection; Vertebrates: nervous system and sense organs; BDNF, brain-derived growth factor; L5, fifth lumbar; PB, phosphate buffer; primary afferents; DRG, dorsal root ganglion; dorsal root axons; nociception; NGF, nerve growth factor; transection; L4, fourth lumbar; Nociception; Peripheral nerve; Spinal cord; Rat; Rodentia; Central nervous system; Myelinated nerve fiber; Posterior spinal root; Vertebrata; Mammalia; Sensory neuron; Lesion; Sciatic nerve
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(96)00528-3

Cutting or crushing rat sciatic nerve does not significantly reduce the number of central myelinated sensory axons in the dorsal roots entering the fourth and fifth lumbar segments even over very extended periods of time. Unmyelinated axons were reduced by ∼50%, but only long after sciatic nerve lesions (four to eight months), and reinnervation of the peripheral target did not rescue these axons. This indicates that a peripheral nerve lesion sets up a slowly developing but major shift towards large afferent fiber domination of primary afferent input into the spinal cord. In addition, since myelinated axons are never lost, this is good evidence that the cells that give rise to these fibers are also not lost. If this is the case, this would indicate that adult primary sensory neurons with myelinated axons do not depend on peripheral target innervation for survival.