Pattern of ongoing activity in rat superior cervical ganglion neurons projecting to a specific target.

The ongoing activity of superior cervical ganglion neurons projecting to the rat submandibular gland was investigated with intracellular techniques. The relevant cells were identified by retrograde labeling with the fluorescent dye DiI placed in the submandibular gland 7-10 days earlier. The majority of labeled cells (89%) were 'silent' during a standard 5-min period of recording. In contrast, only 15% of cells projecting to targets other than the submandibular gland were silent during the standard period of observation. Evidently, ganglion cells innervating different targets have different patterns of activity.