Effect of unsaturated fatty acid on muscarinic current in guinea pig gastric antral circular myocytes.

AIM: To investigate the effect of ectogenesis unsaturated fatty acid on carbachol-induced muscarinic current (ICCh) and its mechanism. METHODS: Using the whole-cell patch-clamp technique, ICCh was recorded in single smooth muscle cell isolated from the antral circular smooth muscles of guinea-pig stomach. RESULTS: Arachidonic acid (AA) was added in external perfusing solution and AA inhibited ICCh to 46 %+/-8 %, 23 %+/-5 %, and 3.8 %+/-0.9 % at 1, 3, and 5 micromol/L. Another unsaturated fatty acid, linoleic acid (LA) also inhibited ICCh in a dose-dependant manner. LA inhibited ICCh to 69 %+/-10 %, 35 %+/-5 %, and 7.4 %+/-1.2 % at 1, 5, and 10 micromol/L, respectively. The same concentration (5 micromol/L) of AA, LA, and oleic acid (OA) suppressed ICCh to 3.8 %+/-0.9 %, 35 %+/-5 %, and 67 %+/-9 %, respectively. The inhibitory potency sequence of these unsaturated fatty acids was AA>LA>OA. After 10-15 min of pretreatment with H-7 (a protein phosphorylation C inhibitor) 100 micromol/L or indomethacin (a cyclooxygenase inhibitor) 10 micromol/L, ICCh was inhibited by 5 micromol/L of AA to 5.5 %+/-0.7 % and 3.0 %+/-1.0 %, respectively. CONCLUSION: The unsaturated fatty acids directly inhibited ICCh, and the inhibitory potency was related to the number of double bonds in fatty acid chain.