The development of synaptophysin-like immunoreactivity in the lumbosacral enlargement of the spinal cord of the opossum Monodelphis domestica

The presence of synaptophysin in the lumbosacral enlargement of developing opossums, Monodelphis domestica, was studied immunohistochemically at the Light microscopic level. In newborn, synaptophysin-labeling was observed in the presumptive white matter, presumably in growing axons, and was scant in the ventrolateral gray matter. Over the next 3 weeks the labeling filled the gray matter following a general ventrodorsal gradient. Labeling was found in the white matter until the fifth week. Synaptogenesis in the lumbosacral enlargement of the opossum thus occurs mostly postnatally, when many descending axons have already reached that level. It is particularly intense in the ventral horn when the hindlimbs begin to move, and in the dorsal horn when sensorimotor reflexes can be elicited. (C) 1998 Elsevier Science B.V.