synaptic corelease of atp and gaba in cultured spinal neurons young-hawan jo and rémy schlichter...
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Synaptic corelease of ATP and GABA in cultured spinal neurons
Young-Hawan Jo and Rémy Schlichter
Laboratoire de Neurophysiologie cellulaire et intégrée, UMR 7519 CNRS, Université Louis Pasteur, 21 rue Descartes, Strasbourg, France
Problem
Introduction Methodology Results Discussion
Sensory
inputs
Touch receptors (skin)
Neuronal
pathway
Somatosensory cortex (SI)
Problem
Introduction Methodology Results Discussion
Roles : Transmission Modulation
Peripheral nociceptive sensory messages
Problem
Introduction Methodology Results Discussion
Inputs
Aδ + C Glutamate + Subtance P (fast and slow)
Local interneurons Glut ou GABA
Electrical stimulation of Iaire afferent ATP release in superficial Dorsal Horn by local interneurons (Sawynok & Downie, 1993, Brain research)
Problem
Introduction Methodology Results Discussion
Expression mRNAs that coding for P2X2, P2X4, P2X6 subunits in Lamina I and II (Collo, 1996, J. Neuroscience)
Problem
Introduction Methodology Results Discussion
ATP may serve as a fast neurotransmitter between superficial
dorsal horn neurons?
Cultured spinal dorsal horn
neurons
10dPerforated
patch-clampIPSP or EPSP
Introduction Methodology
Synaptic transmission
Results Discussion
AP-5 + CNQX + Bicuculine + Strychnine = BSCA
Coreleased ATP-GABA
P2X Rr
GABA Rr
Glutamate Rr
Glycinergique Rr
Pré
Post
Inward currents = EPSPs
-60mV
Interaction ATP-GABA
P2X Rr
GABA Rr
Glutamate Rr
Glycinergique Rr
Pré
Post
Introduction Methodology
Synaptic transmission
Results Discussion
Suramine ou PPADS
Coreleased ATP-GABA
-60mV
Interaction ATP-GABA
Release of ATP acts on P2X Rr
Introduction Methodology
Synaptic transmission
Results Discussion
Differents threshold
Coreleased ATP-GABA
P2X Rr
GABA Rr
Glutamate Rr
Glycinergique Rr
Pré
Post
Reversal potential = 0 mV nonselective cation conductance
Interaction ATP-GABA
Introduction Methodology
Synaptic transmission
Results Discussion
EPSPs
Ca2+ Na+
K+
Reversal potential = 0mV
Coreleased ATP-GABA Interaction ATP-GABA
Pré
Post
Pré
Post
P2X Rr
GABA Rr
Glutamate Rr
Glycinergique Rr
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA
Wash-out CNQX and
AP-5
Wash-out bicuculine
No EPSPs under BSCA
Yes Yes
EPSPs under BSCA
No Yes
I = BSCAII = Whas-out bicuculine
=> ATP is coreleased with GABA
EPSPc No EPSPc
Interaction ATP-GABA
BSCA
EPSP
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA
Pré
Post
Glutamate
No ATP
Pré
Post
Gaba
ATP
Interaction ATP-GABA
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA
Pré
Post
Gaba
ATP
P2X Rr
GABA Rr
If Em = Ex ions flux = 0
=> 70 % of GABAergic synapse corelease ATP
ECl = -90mVEcations = 0 mV
Interaction ATP-GABA
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA Interaction ATP-GABA
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA
Pré
Post
Gaba
Pré
Post
Gaba
70% 30%
Interaction ATP-GABA
P2X Rr
GABA Rr
GABA
ATP
+ spontaneous liberation of GABA and no ATP
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA Interaction ATP-GABA
Post
P2X Rr
GABA Rr
Isoguvacine = Agonist GABAa
ATP = non hydrolysable analog
ATP
Degradation of ATP (metabolite) inhibs IPSP cause
by isoguvacine
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA Interaction ATP-GABA
Post
Isoguvacine = Agonist GABAa
DCPCPX = antagoniste of adenosine RrAdenosineATP
P2X Rr
GABA Rr
Adenosine Rr ATP Adenosine Inhibs GABA IPSP
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA Interaction ATP-GABA
Introduction Methodology
Synaptic transmission
Results Discussion
Coreleased ATP-GABA Interaction ATP-GABA
Adenosine
ATP Pré
Post
Gaba
GABA
5 nucléotidase
-
Adenosine Rr
P2X Rr
GABA Rr
Introduction Methodology Results Discussion
Result are in accord with the fact that P2X receptor mediated excitatory synaptic transmission in 50% of neurons in DH ATP is a prominent NT
ATP is coreleased with GABA
In vivo they don’t find corealesed of ATP and GABA
Important because it doesn’t imply a circuitry to modulate response
Can have implication in a hyperalgesia (repeated stimulation)
Thank you for your
attention
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