The present study examines levels of neurotransmitter messenger RNA (mRNA) at various stages after crush of postganglionic nerves in the superior cervical ganglia. Using complementary DNA (cDNA) probes, we demonstrated a reduction in ganglionic mRNA levels for tyrosine hydroxylase (TH) after axotomy. Concomitantly, actin and tubulin mRNA levels in ganglia were increased. Thus, in neurons of sympathetic ganglia, axotomy appears to be associated with a selective reduction in levels of TH mRNA, and, in turn, alters levels of protein and enzyme activities.