Rubrospinal neurons and retrograde transport of fluoro-gold in acute spinal cord injury--a dose-response curve.

Using the fluorescent tracer Fluoro-Gold, we studied the relationship between severity of spinal cord trauma and the number of retrogradely labeled rubrospinal neurons in the rat. We compared the mean cell counts of retrogradely labeled rubrospinal neurons in rats receiving 0, 20, 40, and 60 g/cm concussive spinal cord traumas. For each incremental increase in trauma a significant reduction in mean cell counts took place (P < 0.0001). We demonstrate a dose-response relationship between trauma severity and Fluoro-Gold retrogradely labeled rubrospinal neurons in acute spinal cord injury of the rat. This relationship may be helpful in quickly assessing the efficacy of therapeutic interventions in acute spinal cord injury. Previous studies with HRP failed to demonstrate such a dose-response curve. Fluoro-Gold may be a more sensitive indicator of neuronal survival than HRP in the traumatized rat spinal cord.