The Journal of Neuroscience, December 7, 2005, ():
Prolonged Reciprocal Signaling via NMDA and GABA Receptors at a Retinal Ribbon Synapse
J. Neurosci. Vigh and von Gersdorff
25: 11412
Supplemental data
Files in this Data Supplement:
- supplemental material
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Figure 1. The tail inward current following depolarizations of the bipolar terminals is not associated with glutamate transporters. A: The non-selective excitatory amino acid transporter blocker TBOA (50 M) did not influence the amount of glutamate release (Cm traces) from the bipolar terminals, nor did it reduce the amplitude of the tail current. Note that the internal solution contained only 20 mM Cl-, so the Cl- current associated with the transporter action should be small. Experiments were carried out in the presence of picrotoxin (100 μM) to block inhibitory feedback. The resting Cm of this terminal was 3.9 pF. B: The tail current on an extended time scale, focusing on the initial segment (dashed box on A). The arrow indicates the place of amplitude measurements. C: Summary diagram of the TBOA effect on the tail current. Open circles represent individual measurements, whereas filled circles show the average ± sd (control: 37.9±10.4 pA, TBOA: 38.3±8.3 pA, n=10, p<0.7, paired Student t-test).
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Figure 2. A working model for the locus and functional coupling between different excitatory and inhibitory ionotropic receptors at the ON-type Mb bipolar cell (BC) terminal to amacrine cell (AC) reciprocal synapse. The dyad synapse consists of one BC synaptic ribbon synapse that faces one ganglion cell (GC) dendrite and one AC bouton. It can also involve two distinct postsynaptic AC processes. The high-affinity NMDA receptors may be located somewhat farther from the glutamate release site (synaptic ribbon), whereas AMPA receptors are facing it. Also, GABAA/c receptors may be activated by trans-synaptic GABA spillover following NMDA receptor activation on AC boutons releasing GABA to (synaptic) GABAA/C receptors.
