Amiloride inhibits contraction and serotonin modulation of Aplysia muscle.
1. Serotonin (5-HT) potentiates acetylcholine (ACh)-elicited contractions of Aplysia buccal muscles. Serotonin potentiation was significantly reduced by 0.03 mM, 0.1 mM, and 0.3 mM amiloride. 2. Unpotentiated ACh-elicited contractions were significantly reduced by 0.1 mM and 0.3 mM amiloride. 3. Amiloride reduced ACh-elicited depolarization. The reduction in contraction caused by 0.3 mM amiloride (to 16% of control) was larger than could be explained by the reduction in depolarization (86% of control). 4. Amiloride had no effect on tension in skinned muscle fibers, indicating that amiloride probably did not have a direct effect on contractile mechanisms. 5. Potentiation of contraction produced by zero sodium (Tris substituted, 0 Na-Tris) medium could be abolished by 0.3 mM amiloride. 6. Zero Na-Tris increased 45Ca influx 2.7-fold. In the presence of 0.3 mM amiloride, 0 Na-Tris increased 45Ca influx only 1.4-fold. 7. Amiloride (0.3 mM) reduced the elevation of muscle cAMP caused by 10(-6) M 5-HT by 60%. Zero Na-Tris did not cause a change in muscle cAMP.
Liu
L X
LX
Department of Physiology, Wayne State University, Detroit, MI 48201.
Anderson
M A
MA
Patel
S
S
Maribao
V
V
Ram
J L
JL
D000109:Acetylcholine / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D002132:Calcium Radioisotopes / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D000242:Cyclic AMP / Q000096:biosynthesis; D004594:Electrophysiology; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D014325:Tromethamine / Q000494:pharmacology
D002132:Calcium Radioisotopes; D014325:Tromethamine; D012701:Serotonin; D000584:Amiloride; D000242:Cyclic AMP; D000109:Acetylcholine