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Cephalopod NeurobiologyNeuroscience Studies in Squid, Octopus and Cuttlefish$
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N. Joan Abbott, Roddy Williamson, and Linda Maddock

Print publication date: 1995

Print ISBN-13: 9780198547907

Published to Oxford Scholarship Online: March 2012

DOI: 10.1093/acprof:oso/9780198547907.001.0001

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Cyclic nucleotide homeostasis and axonal G proteins in the squid Loligo forbesi

Cyclic nucleotide homeostasis and axonal G proteins in the squid Loligo forbesi

Chapter:
(p.35) 3 Cyclic nucleotide homeostasis and axonal G proteins in the squid Loligo forbesi
Source:
Cephalopod Neurobiology
Author(s):

T. J. A. Allen

B. Rouot

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780198547907.003.0025

This chapter reviews studies on signal–transduction coupling in the squid giant axon and its associated Schwann cell sheath, and the role of cyclic nucleotides and G-proteins in this coupling. The cAMP content of the axon is increased by external application of serotonin (5HT), and this effect is modulated by [Ca2+]i and is dependent on internal GTP; membrane G-proteins are implicated in the coupling. Lowering [Mg2+]j attenuates 5HT-evoked adenylate cyclase activity. The giant axon provides too little G-protein for analysis, but it has been possible to demonstrate G-proteins in the richer source of squid optic lobes. The cGMP content of the axon is increased by carbachol, and by nitroprusside, an agent activating cGMP synthesis. The role of G-proteins in Schwann cell-axon signaling is discussed. The study of cyclic nucleotide metabolism in nerve tends to focus on roles in synaptic transmission, with particular emphasis on cAMP and cGMP (cyclic adenosine and guanosine monophosphate, respectively). In this respect, cyclic nucleotides act as messengers or modulators of neurotransmitter function, probably by use of phosphorylation-dephosphorylation reactions. Due to the complexity of mammalian nervous systems it is usually difficult to study these systems in detail and in isolation. The chapter aims to introduce to the reader the usefulness of the squid axon-Schwann cell preparation as a model with which to study certain aspects of signal–transduction coupling.

Keywords:   cyclic nucleotide homeostasis, axonal, G-proteins, Loligo forbesi, cAMP, cGMP, nitroprusside, Schwann cell

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