NITRIC-OXIDE SYNTHASE IN THE AUTONOMIC AND SENSORY GANGLIA INNERVATING THE SUBMANDIBULAR SALIVARY-GLAND

This article reviews the neuroanatomical studies on the distribution o f nitric oxide synthase (NOS) in neurons and nerve fibers innervating the submandibular gland. Specificity of NADPH-diaphorase activity as a histochemical marker of neuronal NOS is discussed in light of corresp onding NOS immunoreactivity. Anatomical data suggest that nitric oxide may affect neural regulation of the submandibular gland through both sympathetic, parasympathetic and sensory divisions of the autonomic ne rvous system. NOS-containing nerve terminals in the gland parenchyme a re mainly vascular and either parasympathetic and/or sensory in nature , while sympathetic terminals lack NOS. Most postganglionic parasympat hetic neurons are intensely NOS-immunoreactive. Some of the preganglio nic parasympathetic neurons show vague reactivity, while their termina ls in the submandibular ganglia stain heavily. The postganglionic symp athetic neurons normally show only barely visible reactivity, while ma nipulations interrupting axonal continuity increase neuronal NOS conte nt. A subpopulation of the preganglionic sympathetic neurons and their terminals are intensely reactive. The observations summarized here su ggest that nitric oxide participates in the control of blood flow thro ugh the gland, while direct effect on secretion is unlikely. (C) 1996 Wiley-Liss, Inc.