TY - JOUR
T1 - Developmental plasticity of ascending spinal axons studies using the north american opossum, Didelphis virginiana
AU - Terman, Jonathan R.
AU - Wang, Xian M.
AU - Martin, George F.
N1 - Funding Information:
The authors wish to thank Drs. L.B. Jakeman and J.S. King for reading early drafts of the manuscript and Ms. Mary Ann Jarrell for technical assistance. Our studies were supported by USPHS Grants NS-25095 and NS-10165.
PY - 1999/1/11
Y1 - 1999/1/11
N2 - The objectives of the present study were to determine if axons of all ascending tracts grow through the lesion after transection of the thoracic spinal cord during development in the North American opossum, and if so, whether they reach regions of the brain they normally innervate. Opossum pups were subjected to transection of the mid-thoracic cord at PD5, PD8, PD12, PD20, or PD26 and injections of Fast Blue (FB) into the lower thoracic or upper lumbar cord 30-40 days or 6 months later. In the PD5 transected cases, labeled axons were present in all of the supraspinal areas labeled by comparable injections in unlesioned, age-matched controls. In the experimental cases, however, labeled axons appeared to be fewer in number and in some areas more restricted in location than in the controls. When lesions were made at PD8, labeled axons were present in the brain of animals allowed to survive 30-40 days prior to FB injections but they were not observed in those allowed to survive 6 months. When lesions were made at PD12 or later, labeled axons were never found rostral to the lesion. It appears, therefore, that axons of all ascending spinal pathways grow though the lesion after transection of the thoracic cord in developing opossums and that they innervate appropriate areas of the brain. Interestingly, the critical period for such growth is shorter than that for most descending axons, suggesting that factors which influence loss of developmental plasticity are not the same for all axons.
AB - The objectives of the present study were to determine if axons of all ascending tracts grow through the lesion after transection of the thoracic spinal cord during development in the North American opossum, and if so, whether they reach regions of the brain they normally innervate. Opossum pups were subjected to transection of the mid-thoracic cord at PD5, PD8, PD12, PD20, or PD26 and injections of Fast Blue (FB) into the lower thoracic or upper lumbar cord 30-40 days or 6 months later. In the PD5 transected cases, labeled axons were present in all of the supraspinal areas labeled by comparable injections in unlesioned, age-matched controls. In the experimental cases, however, labeled axons appeared to be fewer in number and in some areas more restricted in location than in the controls. When lesions were made at PD8, labeled axons were present in the brain of animals allowed to survive 30-40 days prior to FB injections but they were not observed in those allowed to survive 6 months. When lesions were made at PD12 or later, labeled axons were never found rostral to the lesion. It appears, therefore, that axons of all ascending spinal pathways grow though the lesion after transection of the thoracic cord in developing opossums and that they innervate appropriate areas of the brain. Interestingly, the critical period for such growth is shorter than that for most descending axons, suggesting that factors which influence loss of developmental plasticity are not the same for all axons.
KW - Fasciculus gracilis
KW - Marsupial
KW - Regeneration
KW - Spinobulbar
KW - Spinocerebellar
KW - Spinothalamic
UR - http://www.scopus.com/inward/record.url?scp=0033545235&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033545235&partnerID=8YFLogxK
U2 - 10.1016/S0165-3806(98)00162-X
DO - 10.1016/S0165-3806(98)00162-X
M3 - Article
C2 - 9974160
AN - SCOPUS:0033545235
SN - 0165-3806
VL - 112
SP - 65
EP - 77
JO - Developmental Brain Research
JF - Developmental Brain Research
IS - 1
ER -