Journal of Neuroscience, Vol 16, 1614-1622, Copyright © 1996 by Society for Neuroscience
Nitric oxide and peptide neurohormones activate cGMP synthesis in the crab stomatogastric nervous system
NL Scholz, MF Goy, JW Truman and K Graubard
Zoology Department, University of Washington, Seattle 98195-1800, USA.
In the neural circuits that comprise the crustacean stomatogastric nervous
system (STNS), synaptically delivered neurotransmitters and circulating
neurohormones elicit a wide range of rhythmic motor outputs. However,
functional roles for second messengers in this system are poorly
understood. Here we demonstrate two different signaling pathways that
control the synthesis of 3',5'-cGMP in the crab STNS. One pathway is
activated by nitric oxide (NO) and is mediated by a cytoplasmic guanylate
cyclase. A second pathway is stimulated by peptide-containing extracts from
a crab neurohemal organ that activate a membrane-associated guanylate
cyclase. Using whole-mount immunocytochemistry to localize individual
cGMP-containing cells, we find that NO elevates intracellular cGMP in a
small subset of STNS neurons. Immunopositive cells are found predominantly
in the stomatogastric ganglion, with a few additional cells located in the
oesophageal and commissural ganglia. Crab tissues differ in their
sensitivities to NO and to the peptide-containing extract. The NO- mediated
pathway is apparently restricted to the nervous system, whereas the
peptidemediated pathway is present in every tissue tested. The results of
these experiments demonstrate that multiple signaling pathways involving
cGMP are present in the STNS and suggest that this second messenger may
help control the metabolic and physiological status of these motor
circuits.