Nerve growth factor effects on inhibition by submandibular gland ablation or autonomic denervation of activity-induced parotid growth.

Present data confirm our earlier report that an increase in [3H]thymidine incorporation into DNA of parotid gland occurs with reintroduction of solid chow to rats previously maintained on liquid diet; if, however, the submandibular-sublingual glands are removed prior to the dietary substitution, the increase is prevented (present data and [19]). In addition, present data show that administration of nerve growth factor (NGF) to partially sialoadenectomized rats during the 2-day period of dietary change from liquid to solid diet restores thymidine values to the high levels observed following the dietary change in intact animals. However, the increase in gland size that accompanied the change in dietary consistency was not prevented by prior submandibular gland ablation, and administration of NGF had no influence on gland size or cell size. The removal of both the sympathetic and parasympathetic nerves to the parotid gland prior to the dietary manipulation also suppressed [3H]thymidine incorporation into parotid, and values did not differ from chow controls. The data show that NGF, a submandibular growth factor, has a prominent role in regulation of the autonomically-mediated hyperplastic response. However, neither the submandibular gland nor NGF has an important role in regulation of the increase in gland size that also accompanies the dietary change.