Relatively low levels of calpain expression in juvenile rat correlate with less neuronal apoptosis after spinal cord injury

Approximately 5% of spinal cord injuries in the US occur in patients younger than 16 years. These young patients have an increased mortality within the 24 h after trauma but have a greater capacity for functional recovery than adults, suggesting age-related differences in injury tolerance. Unfortunately, the response of the developing cord to secondary injury has not been thoroughly investigated. Calpain, a Ca 2+-dependent protease, has been implicated in the pathogenesis of spinal cord injury (SCI) in rats. Our current investigation revealed that following SCI, calpain upregulation was qualitatively less in the 21-day-old rats than in adult rats, as shown by immunofluorescent labeling. Decreased levels of TUNEL+ neurons were also noted in juvenile rat spinal cord, indicating that the developing cord may have an increased resistance to injury.