A subpopulation of large neurons of the sympathetic superior cervical ganglion innervates the NGF-rich submandibular salivary gland in young adult and aged mice.

One of the main target organs of the sympathetic superior cervical ganglion (SCG) is the submandibular salivary gland, which in male mice has a high concentration of endogenous NGF. To study the subpopulation of SCG neurons which innervate the submandibular glands in young adult and aged mice, a retrograde tracing with a fluorescent dye Fluoro-Gold (Fluorochrome, Englewood, CO, USA) was performed. Fluoro-Gold was introduced into the base of the submandibular salivary gland in anaesthetized animals. Four days later, both ipsilateral and contralateral SCG were studied. The results of the tracing were as follows: (a) in both young adult and aged mice about 45% of the sympathetic neurons of the SCG innervate the ipsilateral submandibular salivary gland; (b) the neurons innervating the submandibular gland form a subpopulation of large-sized neurons; (c) in young adult mice some 10% of SCG neurons innervate the contralateral SCG, while in aged mice only 1-2% have the same effect.