title: Serotonin-activated adenylate cyclase and the possible role of cyclic AMP in modulation of buccal muscle contraction in Aplysia.
abstract: The possible role of cyclic AMP in mediating opposite modulatory effects of serotonin (5-HT) on Aplysia buccal mass muscles E1 and E2 was examined. Serotonin enhances E1 contractions and inhibits E2 contractions. Adenylate cyclase in membranes of both E1 and E2 is stimulated approximately 180% by 10(-6) M 5-HT and 300% by 10(-3) M 5-HT. Dibutyryl cyclic AMP and 8-benzylthio cyclic AMP mimicked the effect of 5-HT on E1 but had no effect on E2. Theophylline (Th) and isobutylmethylxanthine (IBMX) mimicked the effect of 5-HT on E1 at high concentrations. Concentrations of Th and IBMX low enough not to have any direct effect on contraction increased both the magnitude and duration of the effect of 5-HT on E1 contraction. Neither Th nor IBMX had a direct effect on E2 contraction, although Th produced a small increase in the effect of 5-HT on E2. These data are consistent with the hypothesis that cyclic AMP mediates the enhancement effect of 5-HT on E1 contraction. Other mechanisms probably mediate the effect of 5-HT on E2 contraction.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001048:Aplysia; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000201:enzymology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*
chemical_list: D010726:Phosphodiesterase Inhibitors; C024322:8-thio-benzyl cyclic AMP; D012701:Serotonin; D003994:Bucladesine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases