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Ionotropic nicotinic acetylcholine (ACh) receptors have been shown to be modulated by protein kinase-mediated phosphorylation in vitro. Here we demonstrate that 5-hydroxytryptamine (5-HT) can downregulate postsynaptic nicotinic ACh responses, elicited in an identified arthropod motoneuron in situ, by a mechanism dependent on protein kinase activity. Serotonergic modulation can be mimicked by perfusion with membrane-permeable analogues of either adenine (cAMP) or guanine (cGMP) cyclic nucleotides, and is prolonged in the presence of phosphodiesterase inhibitors. Furthermore, suppression of the ACh response by 5-HT is blocked by specific competitive inhibitors of protein kinase A and G, as well as the broad specificity protein kinase inhibitor staurosporine. The protein phosphatase inhibitor cantharidin similarly blocks recovery of the ACh response from suppression mediated by 5-HT. Thus, it appears that the nicotinic ACh response is modulated by a cAMP-mediated phosphorylation-dependent intracellular signalling pathway that is distinct from the direct block of mammalian nicotinic ACh receptors by 5-HT previously reported in vitro.

Original publication




Journal article


Eur J Neurosci

Publication Date





1181 - 1188


Acetylcholine, Animals, Central Nervous System, Cockroaches, Cyclic AMP, Cyclic GMP, Drug Interactions, Electric Stimulation, Enzyme Inhibitors, Free Radical Scavengers, In Vitro Techniques, Male, Membrane Potentials, Motor Neurons, Patch-Clamp Techniques, Phosphorylation, Receptors, Nicotinic, Serotonin, Staurosporine, Synaptic Transmission, Theophylline, Time Factors