Aminergic and peptidergic amplification of intracellular cyclic AMP levels in a molluscan neural network.
1. Serotonin (5-hydroxytryptamine; 5-HT), dopamine (DA), and small cardioactive peptide B (SCPB) can activate adenylate cyclase and increase the intracellular cyclic AMP (cAMP) levels in the Limax procerebrum (PC), with differing time courses and to differing extents. 5-HT and SCPB are potent stimulators of adenylate cyclase, and when both were applied simultaneously, an additive effect was observed. 2. In contrast, DA shows a great variability in the time course of cAMP synthesis and is a weak stimulator. Ergonovine, a DA antagonist, failed to inhibit cyclase activation, indicating that ergonovine-sensitive receptors are absent or ergonovine-sensitive DA receptors are not coupled to adenylate cyclase. 3. 5-HT and SCPB cause a rapid synthesis of cAMP, reaching the maximum 20- to 30-fold increase within a minute. DA's effect is slow in onset and very prolonged, reaching a maximum of only a two- to three-fold increase in the cAMP level. Reasons for variability in DA action are discussed.
D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis*; D004298:Dopamine / Q000494:pharmacology; D004874:Ergonovine / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism; D008974:Mollusca / Q000378:metabolism*; D009415:Nerve Net / Q000187:drug effects / Q000378:metabolism*; D009420:Nervous System / Q000378:metabolism*; D009479:Neuropeptides / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology
D009479:Neuropeptides; D018377:Neurotransmitter Agents; D012701:Serotonin; C041307:small cardioactive peptide B; D000242:Cyclic AMP; D004298:Dopamine; D004874:Ergonovine