GABA-containing sympathetic preganglionic neurons in rat thoracic spinal cord send their axons to the superior cervical ganglion.

摘要

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 sourceof these fibers. No cell body showed mRNAs for glutamic acid decarboxylases (GADs) orimmunoreactivity 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. SinceGAD67-immunoreactive fibers were found not in the dorsal roots or ganglia, but in the ventralroots, GABA-containing fibers in the sympathetic ganglia were considered to originate from thespinal cord. Furthermore, almost all GAD67-immunoreactive fibers in the sympathetic gangliashowed immunoreactivity for vesicular acetylcholine transporter, suggesting that GABA wasutilized by some cholinergic preganglionic neurons. This was confirmed by the following results: 1)after injection of Sindbis/palGFP virus into the intermediolateral nucleus, some anterogradelylabeled fibers in the SCG were immunopositive for GAD67, and 2) after injection of fluorogold intothe SCG, some retrogradely labeled neurons in the thoracic spinal cord were positive for GAD67mRNA. Finally, when the ventral roots of the eighth cervical to the fourth thoracic segments werecut, almost all GAD67- and GABA-immunoreactive fibers disappeared from the ipsilateral SCGand STG, suggesting that the vast majority of GABA-containing fibers in those ganglia were ofspinal origin. Thus, the present findings strongly indicate that some sympathetic preganglionic neurons are not only cholinergic, but also GABAegic