The Journal of Neuroscience, January 1, 1998, 18(1):339-355
Development of Walking, Swimming and Neuronal Connections after
Complete Spinal Cord Transection in the Neonatal Opossum,
Monodelphis domestica
N. R.
Saunders1,
P.
Kitchener1,
G. W.
Knott1,
J. G.
Nicholls2,
A.
Potter1, and
T. J.
Smith1
1 Division of Anatomy and Physiology, University of
Tasmania, Hobart, Tasmania 7001, Australia, and
2 Biozentrum der Universität Basel, CH-4056 Basel,
Switzerland
Development of coordinated movements was quantitatively assessed in
adult opossums (Monodelphis domestica) with thoracic
spinal cords transected by (1) crushing 7-8 d after birth [postnatal days 7-8 (P7-P8)]; at 2-3 years of age, systematic behavioral tests
(e.g., climbing, footprint analysis, and swimming) showed only minor
differences between control (n = 5) and operated
(n = 10) animals; and (2) cutting on P4-P6; at 1 month these opossums exhibited coordinated walking movements but were
unable to right themselves from a supine position, unlike controls
(n = 6). When tested at 2 or 6 months, they could
right themselves and showed remarkable coordination, albeit with more
differences from controls than after a crush. No animals with spinal
cords that were crushed at P14-18 survived because of cannibalism by
the mother. Morphological studies (n = 10) 3 months-3 years after crush at 1 week showed restoration of structural
continuity and normal appearance at the lesion site. Animals with cut
rather than crushed cords showed continuity but greater morphological
deficits. That lesions were complete was demonstrated by examining
morphology and nerve impulse conduction immediately after crushing or
cutting the spinal cord in controls. After lumbar spinal cord injection
of 10 kDa dextran amine, retrogradely labeled cells were found rostral
to the lesion in hindbrain and midbrain nuclei. Conduction was restored
across the site of the lesion. Thus complete spinal cord transection in
neonatal Monodelphis was followed by development of
coordinated movements and repair of the spinal cord, a process that
included development of functional connections by axons that crossed
the lesion.
Key words:
Monodelphis domestica; behavior after spinal
injury; regeneration; response to injury; spinal cord injury; neurite
outgrowth
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