GABA-containing fibers have been observed in the rat superior cervical ganglion (SCG) and,
to a lesser extent, in the stellate ganglion (STG). The aim of present study is to clarify the source
of these fibers. No cell body showed mRNAs for glutamic acid decarboxylases (GADs) or
immunoreactivity for GAD of 67 kDa (GAD67) in the cervical sympathetic chain. Thus,
GABA-containing fibers in the ganglia are suggested to be of extraganglionic origin. Since
GAD67-immunoreactive fibers were found not in the dorsal roots or ganglia, but in the ventral
roots, GABA-containing fibers in the sympathetic ganglia were considered to originate from the
spinal cord. Furthermore, almost all GAD67-immunoreactive fibers in the sympathetic ganglia
showed immunoreactivity for vesicular acetylcholine transporter, suggesting that GABA was
utilized by some cholinergic preganglionic neurons. This was confirmed by the following results: 1)
after injection of Sindbis/palGFP virus into the intermediolateral nucleus, some anterogradely
labeled fibers in the SCG were immunopositive for GAD67, and 2) after injection of fluorogold into
the SCG, some retrogradely labeled neurons in the thoracic spinal cord were positive for GAD67
mRNA. Finally, when the ventral roots of the eighth cervical to the fourth thoracic segments were
cut, almost all GAD67- and GABA-immunoreactive fibers disappeared from the ipsilateral SCG
and STG, suggesting that the vast majority of GABA-containing fibers in those ganglia were of
spinal origin. Thus, the present findings strongly indicate that some sympathetic preganglionic neurons are not only cholinergic, but also GABAegi
