Developmental expression of spontaneous activity in the spinal cord of postnatal opossums, Monodelphis domestica: an anatomical study.
Using Sulforhodamine-101 (SR101) labeling and calcium imaging on in vitro preparations, we investigated the development of spontaneous activity in the spinal enlargements of a marsupial born more immature than eutherian mammals, the opossum Monodelphis domestica. Following the retrograde transport of Calcium Green dye from the limb nerves, we observed the occurrence of spontaneous calcium waves activating the motor columns of the cervical enlargement of opossums aged from P3 to P15 (day of birth: P0) and of the lumbar enlargement from at least P6 to P12. In other preparations, SR101 was added to the bath to identify the active cells. In P1 opossums, only a few SR101-labeled cells were observed in the cervical enlargement and none in the lumbar enlargement. At P5, their number increased cervically and they appeared in the lumbar enlargement. Motoneurons were the major cell type labeled by SR101 but dye leakage made their quantification inaccurate. SR101-labeled cells also occurred elsewhere in the ventral and dorsal grey. Their number increased until P12-14 in both enlargements and then decreased to disappear by P21, the last age examined. Thus in contrast to eutherian mammals, in which spontaneous activity is mostly prenatal, spontaneous activity occurs predominantly postnatally in opossums. It increases at the time when connections from the brain begin to impinge on spinal neurons and when the limbs, especially the hindlimbs, start moving and then decreases as the systems mature.
Lavallée
Annie
A
Département de Sciences biologiques, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, Québec, Canada.
Pflieger
Jean-François
JF
D000200:Action Potentials / Q000502:physiology; D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D004396:Coloring Agents; D005121:Extremities / Q000294:innervation*; D008394:Marsupialia / Q000033:anatomy & histology / Q000254:growth & development; D048309:Monodelphis / Q000033:anatomy & histology / Q000254:growth & development*; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism; D009415:Nerve Net / Q000166:cytology / Q000254:growth & development*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009930:Organic Chemicals; D012235:Rhodamines; D013045:Species Specificity; D013116:Spinal Cord / Q000166:cytology / Q000254:growth & development*; D013194:Staining and Labeling / Q000379:methods
D004396:Coloring Agents; D009930:Organic Chemicals; D012235:Rhodamines; C071336:calcium green; C050829:sulforhodamine 101; D002118:Calcium