BILATERAL PHASIC INCREASES IN DORSAL-ROOT GANGLIA NERVE GROWTH-FACTORSYNTHESIS AFTER UNILATERAL SCIATIC-NERVE CRUSH

The amount of nerve growth factor (NGF) in the L5, L6, and cervical do rsal root ganglia of rats was examined from 1 to 30 days after a unila teral crush lesion of the sciatic nerve and adjacent branches of the l umbar plexus at the level of the sciatic notch. Unilateral nerve crush produced increases in NGF content of lumbar ganglia at 1, 4, and 7-8 days after injury, with increased NGF mRNA at 4 and 7-8 days. Increase s in NGF at 1 and 4 days were most pronounced on the unlesioned side w hile increases at days 7 and 8 were most pronounced on the lesioned si de. NGF content increased in cervical ganglia of nerve-lesioned animal s at 3 and 7 days after injury and in lumbar and cervical ganglia of s ham-operated animals 3-5 days after surgery, with no comparable change s in NGF mRNA. Elevations of ganglionic NGF coincide temporally with s ome of the alterations in metabolism and morphology which occur in dor sal root ganglion neurons after sciatic nerve crush. However, the bila teral nature of increases in NGF demonstrates that the factor(s) produ cing the response is not restricted to ganglia axotomized by the injur y. The data suggest that ganglionic NGF may be regulated by systemic f actors, produced during stress or trauma, as well as by factors from t he denervated target tissue and/or regenerating axons.