Simultaneous expression of the SP-peptidergic and noradrenergic phenotypes in rat sympathetic neurons.

We previously observed that substance P (SP) levels in the rat superior cervical ganglion (SCG) rise sharply when the ganglion is maintained in vitro. To define the cellular localization of SP, sections of cultured SCG were stained for the possible dual presence of SP and tyrosine hydroxylase (TOH). Immunoreactivity to both SP and TOH was present in the majority of principal neurons. This observation suggests that principal sympathetic neurons can express simultaneously both the noradrenergic and SP-peptidergic phenotypes.