Enkephalinergic sympathetic and parasympathetic innervation of the rat submandibular and sublingual glands.

Enkephalinergic innervation of the rat salivary glands was investigated by immunocytochemical techniques. Based upon immunostaining for enkephalin (ENK) and tyrosine hydroxylase (TH), 4 types of neurons could be distinguished in the submandibular ganglion: cells containing both ENK and TH (9% of all ganglion cells), cells containing only ENK (17%), cells containing only TH (4%) and cells lacking both ENK and TH (70%). Almost all of the ganglion neurons were also positive for AChE and so were most of the TH-positive cells. The ENK-positive fibers outnumbered the TH-positive fibers. Although TH-positive fibers displayed concurrent ENK immunoreactivity, fibers in the blood vessel walls were only immunoreactive for TH. Excision of the superior cervical ganglion resulted in a decrease of ENK fibers and the disappearance of most of the TH fibers from the submandibular gland. Most of the remaining ENK-positive fibers were immunonegative for TH, while the remaining TH-positive fibers were also positive for ENK. The salivary gland of the postnatal 8-week-old rats had a considerable number of ENK-positive neurons and fibers in the submandibular ganglion and acini.