Co-existence of muscarinic and nicotinic receptors and their functional interaction in mouse Beta-TC6 cells

• Published in: European journal of pharmacology 2009-02, Vol.604 (1), p.150-157
• Main Authors: Ohtani, Masahiro, Daly, John W., Oka, Takami
• Format: Article
• Language: English
• Subjects: Animals; Calcium; Calcium - metabolism; Carbamylcholine; Cell Line, Tumor; Cytoplasm - drug effects; Cytoplasm - metabolism; Insulin - metabolism; Insulin Secretion; Mice; Muscarinic Agonists - pharmacology; Muscarinic Antagonists - pharmacology; Muscarinic receptor; Nicotine; Nicotinic Agonists - pharmacology; Nicotinic Antagonists - pharmacology; Oxotremorine M; Receptors, Muscarinic - biosynthesis; Receptors, Muscarinic - metabolism; Receptors, Muscarinic - physiology; Receptors, Nicotinic - biosynthesis; Receptors, Nicotinic - metabolism; Receptors, Nicotinic - physiology; Reverse Transcriptase Polymerase Chain Reaction
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2008.12.018

Mouse Beta-TC6 insulinoma cells possessing nicotinic receptor [Ohtani, M., Oka, T., Badyuk, M., Xiao, Y., Kellar, KJ., Daly, JW., 2006. Mouse β-TC6 insulinoma cells: high expression of functional α3β4 nicotinic receptors mediating membrane potential, intracellular calcium, and insulin release. Mol. Pharmacol. 69, 899–907.] also expressed M 3 and M 4 muscarinic receptors. Carbamylcholine, a mixed muscarinic/nicotinic receptor agonist, or oxotremorine M, a selective muscarinic agonist, elicited an elevation of cytoplasmic Ca 2+ concentration ([Ca 2+] i) and release of insulin. The maximal [Ca 2+] i response induced by carbamylcholine was larger than that of oxotremorine M or that of nicotine, suggesting that carbamylcholine enhanced the [Ca 2+] i response by stimulating two types of receptor. M 3 and M 4 muscarinic receptor antagonists inhibited the [Ca 2+] i responses to carbamylcholine and oxotremorine M, suggesting the involvement of these muscarinic receptors in the regulation of [Ca 2+] i. In addition, pretreatment with carbamylcholine inhibited the [Ca 2+] i responses to oxotremorine M or nicotine, indicating that the effect of carbamylcholine on [Ca 2+] i was mediated by both muscarinic and nicotinic receptors. A phospholipase C (PLC) inhibitor U73122, a protein kinase C (PKC) inhibitor chelerythrine and a phospholipase A 2 (PLA 2) inhibitor AACOCF 3 inhibited the [Ca 2+] i response to carbamylcholine or oxotremorine M, while these inhibitors did not block the effect of nicotine. Carbamylcholine induced a smaller extent of insulin secretion than oxotremorine M, suggesting that concomitant stimulation of muscarinic and nicotinic receptors by carbamylcholine resulted in the negative type of the receptor interaction.