Differences in morphology and neuropeptide immunoreactivity of superior cervical ganglion neurons that innervate the major salivary glands in rats

Abstract

A neuronal tracer, WGA-HRP, was injected into the rat parotid gland (PG), submandibular gland (SMG), and sublingual gland (SLG) to label the superior cervical ganglion (SCG) neurons, and the number, size of soma, dendritic arborization and immunoreactivities (IR) of vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) were investigated. The number and size of neurons projecting into SMG were greater than those of neurons projecting into the PG or SLG. The PG and SLG projecting neurons did not show significant differences in their number and size of soma, even the weight of the SLG was much smaller than the other two glands. The total length of dendrites of the SMG projecting neurons was greater than those of the PG or SLG projecting neurons. PG and SLG projecting neurons showed no significant difference in the total length of their dendrites. PG and SLG projecting neurons with NPY-IR were larger in number than SMG projecting neurons. SLG projecting neurons with VIP-IR were greater in number than neurons projecting into the other two glands. Our results indicate the differences in morphology and neuropeptide immunoreactivities among the SCG neurons which may be due to the differences in the neuronal functions and the participation of neurotrophic factors.