Neuroscience 2003 Abstract
| Presentation Number: | 691.2 |
|---|---|
| Abstract Title: | Induction of postsynaptically silent synapses by an astrocyte factor. |
| Authors: |
Ullian, E. M.*1
; Christopherson, K. S.1
; Stokes, C.1
; Mullowney, C.1
; Barres, B. A.1
1NeuroBiol., Stanford Univ., Stanford, CA |
| Primary Theme and Topics |
Synaptic Transmission and Excitability - Glia -- Other |
| Secondary Theme and Topics | Synaptic Transmission and Excitability<br />- Synaptic Transmission<br />-- Postsynaptic mechanisms: Excitatory |
| Session: |
691. Synaptic Transmission and Excitability: Glia II Poster |
| Presentation Time: | Tuesday, November 11, 2003 2:00 PM-3:00 PM |
| Location: | Morial Convention Center - Hall F-I, Board # D85 |
| Keywords: | SYNAPTOGENESIS, RETINAL GANGLION CELL, GLIA, SYNAPTIC TRANSMISSION |
How is synapse number regulated? We have determined the identity of a secreted astrocyte factor that increases the number of synapses made by purified CNS neurons 3-5 fold (Christopherson et al, 2003 SFN abstract). Surprisingly these synapses are not active as measured by patch-clamp recordings of spontaneous mEPSCs. To determine why the synapses are not active, we measured presynaptic function first by measuring the number of synaptic sites that recycle vesicles using an antibody to the luminal domain of synaptotagmin. We found that synapses induced by this astrocyte factor do recycle vesicles, and that there are a comparable number of active synapses induced by this factor and by astrocyte conditioned media. We also investigated the kinetics of presynaptic vesicle recycling using the styryl dye FM1-43. We found that synapses induced by either the purified factor or astrocyte-conditioned media have similar kinetics. To determine if the synapses on these neurons are postsynaptically active, we measured the whole-cell response to applied L-glutamate. We found that neurons treated with the purified factor had much smaller responses to L-glutamate than did neurons treated with astrocyte feeding layers. In addition, average mini size is reduced in neurons treated with the purified factor. To ensure that these synapses are ultrastructurally normal we examined synaptic structure using EM. We found no significant difference in the ultrastructure of synapses induced by the purified factor or by astrocyte feeding layers. Taken together, these data indicate that this newly identified astrocyte factor is sufficient to induce structural, but not functional, synapses, similar to the “silent” synapses that have been described during development in vivo. Therefore, it appears that distinct signals are necessary to induce ultrastructurally normal synapses vs. electrically active synapses.
Supported by NIDA R01 (BAB), NEI NRSA (KSC), and a Zaffaroni grant (EMU)
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2003 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2003. Online.
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