Effects of autonomic antagonists and growth factors on activity-mediated hyperplasia of rat parotid

Administration of the autonomic antagonists atropine (1 mg/kg body wt), propranolol (2 mg/kg body wt), and phenoxybenzamine (2 mg/kg body wt) before the dietary change from all liquid to solid chow prevented an increase in uptake of [3H]thymidine into DNA of rat parotid gland associated with this dietary change. Administration of either the cholinergic antagonist alone or the adrenergic antagonists alone produced partial inhibition. The effects of complete autonomic blockade were not reversed when nerve growth factor (NGF) or epidermal growth factor (EGF) was given immediately after administration of antagonists. The effects of complete autonomic blockade were similar to those seen with surgical removal of the autonomic nerves to the parotid. The increased levels of beta 1-4-galactosyltransferase seen with the dietary change were not evident in rats given both muscarinic and adrenergic antagonists before the change to solid food nor did NGF or EGF reverse these inhibitory effects. Histological observation showed that the surgically denervated gland was morphologically less homogenous than the gland of rats given the antagonists and had infiltrating connective tissue. Nonetheless, with the reduced acinar cell pool, the [3H]thymidine uptake of the denervated parotid and that of antagonist-injected animals was similar.