Potential regulation by trophic factors of low-affinity NGF receptors in spinal motor neurons.
Developing spinal motor neurons (SMN) express low-affinity nerve growth factor receptors (LNGFR) but not high-affinity transducing NGF receptors. Moreover, SMN are not supported by NGF in vitro. In the normal adult rat most SMN are not LNGFR immunoreactive (LNGFR-IR), but they transiently reexpress LNGFR (though not the high-affinity receptor) after peripheral nerve injury. With a cut lesion of the sciatic nerve (when only a neuroma forms), the number of LNGFR-IR SMN at L4-L6 rapidly increases to a maximum between day 1 and 7 and returns to baseline levels by day 30. After a crush lesion (accompanied by regeneration to the muscle), LNGFR-IR SMN appear in about the same numbers, but they start to disappear 1 week later. We speculate that the similar appearance and differential decline of LNGFR-IR seen after the two types of lesions are regulated by the availability of a common signal such as ciliary neurotrophic factor. The adult SMN model provides a good opportunity to investigate the reexpression of LNGFR after peripheral nerve injury, and more generally, the unknown role and regulation of LNGFR.
Hagg
T
T
Department of Biology, University of California, San Diego 92093-0601.
Rende
M
M
Magal
E
E
Burnham
P
P
Oudega
M
M
Varon
S
S
D000818:Animals; D009046:Motor Neurons / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000502:physiology*; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D013119:Spinal Cord Injuries / Q000378:metabolism / Q000473:pathology
D009414:Nerve Growth Factors; D017475:Receptors, Nerve Growth Factor