Locus coeruleus neuron growth cones and spinal cord regeneration.

One of the major impediments to successful recovery of function after a spinal cord injury is thought to be the reaction of the neuronal growth cone to inhibitory influences in the local environment in or around the site of the injury. The growth cones of locus coeruleus neurons studied in vitro collapsed upon contact with an extract of CNS myelin but did not collapse on contact with an extract of PNS myelin. Coincident with the collapse of the growth cone, was an increase in internal free calcium concentration that was predominantly the result of an influx of calcium through channels in the plasma membrane. Omega-conotoxin, which specifically blocks N-type voltage-gated calcium channels, blocked both the myelin-induced calcium influx and the coincident collapse of the growth cone.