Effects of electrical stimulation of the sympathetic nerve on the levels of β-adrenergic and cholinergic muscarinic receptors and cyclic nucleotides in rat salivary glands

Abstract

After 30 and 60 min of stimulation, there were decreases of 16 to 19 per cent in β-adrenoceptors in rat submandibular and parotid glands; a 10-min stimulation caused no change. Pre-incubation of the reaction mixtures (stimulated glands) with atenolol, a β 1-antagonist, prevented most dihydroalprenolol (DHP) binding, but with butoxamine, a β 2-antagonist, DHP binding was nearly complete. Thus the β-receptor was of the β 1-subtype. Muscarinic receptors of parotid gland showed no change after 10 min stimulation; after 30 min there was an increase of 12 per cent, and after 60 min, of 28 per cent. With submandibular gland, there was also no change at 10 min but, at 30 min, there was a 25 per cent increase, and at 60 min, a decrease of 18 per cent. Cyclic-AMP levels of parotid gland were markedly elevated after 10 min of stimulation (9-fold increase above controls) but, at 30 and 60 min, there was only a 1.6-fold increase. In submandibular gland, cyclic-AMP increased 10-fold at 10 min; at 30 min it was 2.5 times control levels and at 60 min, 1.9 times. Cyclic-GMP levels of parotid gland increased 34-fold after 30 or 60 min of nerve stimulation, but only 1.6-fold at 10 min. With submandibular gland, there was a 22-fold increase at 10 min, but at 30 and 60 min this was 15- and 12-fold, respectively. Thus β-adrenergic and muscarinic receptor densities and levels of cyclic AMP and CMP change after acute stimulation of the sympathetic nerve to the rat salivary glands; increases in levels of both nucleotides precede the changes in receptor number.