STIMULATION BY NERVE GROWTH-FACTOR OF NEUROPEPTIDE SYNTHESIS IN THE ADULT-RAT IN-VIVO - BILATERAL RESPONSE TO UNILATERAL INTRAPLANTAR INJECTIONS

Unilateral intraplantar injections (1/day for 3 days) of 4 mu g nerve growth factor (NGF) into the rat hindpaw increased the expression of p repro-tachykinin (PPT)- and prepro-calcitonin gene-related peptide (pp CGRP)-mRNA in bilateral L(5) dorsal root ganglia (DRGs). This was acco mpanied by an increase of CGRP-like immunoreactivity in the ipsi- and contralateral sciatic nerve but by no detectable change of CGRP-IR in other afferents. NGF injections into the skin of one ear or into the p lantar side of one forepaw increased CGRP-IR in the respective afferen ts (trigeminal ganglion, or nerves arising from the brachial plexus, r espectively), but had no effect on sciatic CGRP-IR. This suggests that the NGF-induced symmetrical increase of CGRP synthesis in L(5) DRGs w as not caused by systemic action of NGF, which, therefore, may be a us eful tool to further investigate mechanisms which are responsible for contralateral effects of unilateral inflammation.