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Distribution of vesicle pools in cerebellar parallel fibre terminals after depression of ectopic transmission

Dobson, Katharine L.; Smith, Zoe H.; Bellamy, Tomas C.


Katharine L. Dobson

Zoe H. Smith


Jean-Pierre Mothet


At parallel fibre terminals in the cerebellar cortex, glutamate released outside of the active zone can activate AMPA receptors on juxtaposed Bergmann glial cell processes. This process is termed “ectopic” release, and allows for directed transmission to astroglial cells that is functionally independent of synaptic transmission to postsynaptic Purkinje neurons. The location of ectopic sites in presynaptic terminals is uncertain. Functional evidence suggests that stimulation of parallel fibres at 1 Hz exhausts ectopic transmission due to a failure to rapidly recycle vesicles to the ectopic pool, and so would predict a loss of vesicles in the near vicinity of extrasynaptic glial processes. In this study we used this stimulation protocol to investigate whether the distribution of vesicles within the presynaptic terminal is altered after suppression of ectopic release. Stimulation at 1 Hz had only a minor impact on the distribution of vesicles in presynaptic terminals when analysed with electron microscopy. Vesicle number and terminal size were unaffected by 1 Hz stimulation, but the relative abundance of vesicles in close proximity to the active zone was marginally reduced. In contrast, the fraction of vesicles facing glial membranes was unchanged after suppression of ectopic transmission. 1 Hz stimulation also resulted in a small but statistically-significant increase in the distance between glial membrane and presynaptic terminal, suggesting withdrawal of glial membranes from synapses is detectable in ultrastructural anatomy within minutes. These results raise doubts about the location of ectopic release sites, but indicate that neuron-glial association varies on a dynamic time scale.


Dobson, K. L., Smith, Z. H., & Bellamy, T. C. (2018). Distribution of vesicle pools in cerebellar parallel fibre terminals after depression of ectopic transmission. PLoS ONE, 13(7), 1-15.

Journal Article Type Article
Acceptance Date Jul 5, 2018
Online Publication Date Jul 19, 2018
Publication Date Jul 19, 2018
Deposit Date Oct 26, 2018
Publicly Available Date Oct 26, 2018
Journal PLOS ONE
Electronic ISSN 1932-6203
Publisher Public Library of Science
Peer Reviewed Peer Reviewed
Volume 13
Issue 7
Article Number e0200937
Pages 1-15
Keywords General Biochemistry, Genetics and Molecular Biology; General Agricultural and Biological Sciences; General Medicine
Public URL
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