Abstract
To investigate whether naloxone has the effects on the spinal cord contusion injury, a contusive spinal cord injury (SCI) was made in female Wistar rats with a weight (20 g, 2.5 mm diameter, 50 mm height) after laminectomy at Th 9/10. Naloxone (dissolved in 50% ethanol) was treated using osmotic pump (0.1 mg/day for 7 days, s.c.) that was implanted in the dorsal side of the neck at 4 hours before SCI. Early improvement in BBB score was found in the naloxone-treated group compared with controls. Rats were sacrificed at 1 day, 3 days, 9 days and 2 weeks after SCI, and offered for immunohistochemical staining using a microglial marker (OX-41), oligodendrocyte (OL) progenitor markers (NG2, O4) and degraded myelin basic protein marker (MBP-D). The number of NG2 and O4 positive cells in regions at 10 mm caudal to the lesion was not significantly different between the naloxone-treated group and controls. Number of MBP-D positive cells especially in the ventral white matter at 1 day and OX-41 positive cells at 9 days were significantly decreased in the naloxone-treated groups. In the naloxone-treated group, most of microglial cells showed ramified morphology in the ventral horn at 9 days after SCI. Data suggest that treatment with naloxone facilitated early functional recovery after SCI partly with modification of microglial function. [Jpn J Physiol 54 Suppl:S182 (2004)]
