Noncompetitive inhibition by camphor of nicotinic acetylcholine receptors |
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Authors: | Park T J Seo H K Kang B J Kim K T |
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Institution: | Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, San 31, Hyoja Dong, 790-784, Pohang, Korea. ktk@postech.ac.kr |
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Abstract: | The effect of camphor, a monoterpenoid, on catecholamine secretion was investigated in bovine adrenal chromaffin cells. Camphor inhibited 3H]norepinephrine (3H]NE) secretion induced by a nicotinic acetylcholine receptor (nAChR) agonist, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), with a half-maximal inhibitory concentration (IC50) of 70 +/- 12 microM. In addition, camphor inhibited the rise in cytosolic calcium (Ca2+]i) and sodium (Na+]i) induced by DMPP with IC50 values of 88 +/- 32 and 19 +/- 2 microM, respectively, suggesting that the activity of nAChRs is also inhibited by camphor. On the other hand, binding of 3H]nicotine to nAChRs was not affected by camphor. Ca2+]i increases induced by high K+, veratridine, and bradykinin were not affected by camphor. The data suggest that camphor specifically inhibits catecholamine secretion by blocking nAChRs without affecting agonist binding. |
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