Neuronal conduction of excitation without action potentials based on ceramide production.
BACKGROUND
Action potentials are the classic mechanism by which neurons convey a state of excitation throughout their length, leading, after synaptic transmission, to the activation of other neurons and consequently to network functioning. Using an in vitro integrated model, we found previously that peripheral networks in the autonomic nervous system can organise an unconventional regulatory reflex of the digestive tract motility without action potentials.


RESULTS
In this report, we used combined neuropharmacological and biochemical approaches to elucidate some steps of the mechanism that conveys excitation along the nerves fibres without action potentials. This mechanism requires the production of ceramide in membrane lipid rafts, which triggers in the cytoplasm an increase in intracellular calcium concentration, followed by activation of a neuronal nitric oxide synthase leading to local production of nitric oxide, and then to guanosine cyclic monophosphate. This sequence of second messengers is activated in cascade from rafts to rafts to ensure conduction of the excitation along the nerve fibres.


CONCLUSIONS
Our results indicate that second messengers are involved in neuronal conduction of excitation without action potentials. This mechanism represents the first evidence-to our knowledge-that excitation is carried along nerves independently of electrical signals. This unexpected ceramide-based conduction of excitation without action potentials along the autonomic nerve fibres opens up new prospects in our understanding of neuronal functioning.
Fasano
Caroline
C
Laboratoire de Physiologie Neurovégétative, UMR CNRS 6153-INRA 1147, Institut Fédératif de Recherche Jean Roche IFR 11, Université Paul Cézanne, Aix-Marseille III, Faculté des Sciences et Techniques, Marseille, France.
Tercé
François
F
Niel
Jean-Pierre
JP
Nguyen
Thi Thu Hang
TT
Hiol
Abel
A
Bertrand-Michel
Justine
J
Mallet
Nicole
N
Collet
Xavier
X
Miolan
Jean-Pierre
JP
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002518:Ceramides / Q000096:biosynthesis*; D006152:Cyclic GMP / Q000502:physiology; D004386:Duodenum / Q000294:innervation / Q000502:physiology*; D021962:Membrane Microdomains / Q000502:physiology; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology; D051381:Rats; D015290:Second Messenger Systems / Q000502:physiology*; D013270:Stomach / Q000294:innervation / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D002518:Ceramides; D009569:Nitric Oxide; D006152:Cyclic GMP