Depression of parallel and climbing fiber transmission to Bergmann glia is input specific and correlates with increased precision of synaptic transmission
Article first published online: 3 OCT 2008
Copyright © 2008 Wiley-Liss, Inc.
Volume 57, Issue 4, pages 393–401, March 2009
How to Cite
Balakrishnan, S. and Bellamy, T. C. (2009), Depression of parallel and climbing fiber transmission to Bergmann glia is input specific and correlates with increased precision of synaptic transmission. Glia, 57: 393–401. doi: 10.1002/glia.20768
- Issue published online: 10 JAN 2009
- Article first published online: 3 OCT 2008
- Manuscript Accepted: 5 AUG 2008
- Manuscript Received: 29 MAY 2008
- Biotechnology and Biological Sciences Research Council, UK
- synaptic plasticity;
In the cerebellar cortex, Bergmann glia enclose the synapses of both parallel and climbing fiber inputs to the Purkinje neuron. The glia express Ca2+-permeable AMPA receptors, and the GLAST and GLT-1 classes of glutamate transporter, which are activated by glutamate released during synaptic transmission. We have previously reported that parallel fiber to Bergmann glial transmission in rat cerebellar slices exhibits a form of frequency-dependent plasticity, namely long-term depression, following repetitive stimulation at 0.1–1 Hz. Here, we report that this form of plasticity is also present at the climbing fiber input, that climbing and parallel fibers can be depressed independently, that discrete parallel fiber inputs can also be depressed independently, and that depression is maintained when a distributed array of parallel fibers are stimulated (in contrast to several forms of synaptic plasticity at the Purkinje neuron). Depression of glutamate transporter currents does not correlate with a decrease in the stringency with which Purkinje neuron synapses are isolated. Rather, postsynaptic currents in Purkinje neurons decay more rapidly and perisynaptic metabotropic glutamate receptors are activated less effectively after stimulation at 0.2 and 1 Hz, suggesting that depression arises from a decrease in extrasynaptic glutamate concentration and not from impairment of glutamate clearance in and around the synapse. These results indicate that neuron-glial plasticity is activity dependent, input specific and does not require spillover between adjacent synapses to manifest. They also argue against a withdrawal of the glial sheath from synaptic regions as the putative mechanism of plasticity. © 2008 Wiley-Liss, Inc.