Neurotrophic activity in the central and peripheral nervous systems of the cat. Effects of injury.

Neurotrophic activity for ciliary ganglion neurons in culture was found in both central and peripheral nervous system of the cat. The activity found in extracts of spinal cord supported the survival of 100% of the test neurons during 24 h and was characterized by a slope of -56 +/- 13 in the linear portion of the dose-response curve. Sciatic nerve extract supported the survival of only 60% of the test neurons; it dose-response curve had a slope of -20 +/- 4. Extracts of meninges, spinal rootlets, dorsal root ganglia and muscle supported 100% of the test neurons; two slopes were observed in their dose-response curves, which coincided with those of spinal cord and sciatic nerve dose-response curves. The two different slopes may correspond to two different active molecules, tentatively denominated I and II, having distinct distributions in the assayed tissues. In the spinal cord, both direct injury and deafferentation led to increases in neurotropic activity. In the peripheral nervous system, transections leading to death of dorsal root ganglion neurons or to degeneration of their axons were accompanied by decreases in activity II. Activity I in dorsal roots and dorsal root ganglia was unaffected by injury and may be associated with non-neuronal cells or extracellular matrix components.