title: Short-term plasticity of Bergmann glial cell extrasynaptic currents during parallel fiber stimulation in rat cerebellum.
abstract: Bergmann glial cells (BGC) enclose the synapses of Purkinje neurons (PN) and interneurons in the molecular layer of the cerebellar cortex. During synaptic transmission, glutamate evokes inward currents in the glia by activation of Ca2+-permeable aminohydroxymethylisoxazole propionic acid receptors (AMPAR) and electrogenic transporters. We describe the plasticity of BGC currents during paired-pulse and repetitive stimulation of parallel fibers in cerebellar slices. Paired-pulse facilitation (PPF) of BGC AMPAR currents was 4-fold, twice that of PN PPF. Experiments with a low-affinity AMPAR antagonist showed an increase in extrasynaptic glutamate concentration during the second pulse of the pair. PPF of glial transporter currents was 1.8-fold, similar to synaptic PPF. Tetanic stimulation revealed that facilitation of BGC AMPAR currents is not sustained during high-frequency stimulation, and substantial depression is observed after a few pulses. Consequently, Ca2+ influx through glial AMPARs would initially be facilitated but subsequently depressed, generating a transient Ca2+ influx in response to a sustained tetanus. This pattern of plasticity may be important in enabling Bergmann glial cell processes to detect and support synapses with high-frequency input. Finally, a new current was observed in BGC during repetitive stimulation. It was blocked by NBQX and intracellular GDP-beta-S, increased by glutamate uptake inhibition, had PPF similar to synaptic PPF, and was unaffected by an inhibitor of fast glial AMPAR currents. The evidence suggests that activation of neuronal AMPARs causes the release of a paracrine messenger to activate a G-protein coupled receptor in the BGC.
authors.affiliation: National Institute for Medical Research, London, United Kingdom. tom.bellamy@bbsrc.ac.uk
authors.forename: Tomas C
authors.initials: TC
authors.lastname: Bellamy
authors.forename: David
authors.initials: D
authors.lastname: Ogden
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D002525:Cerebellar Cortex / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D019899:Paracrine Communication / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000187:drug effects / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D043562:Receptors, G-Protein-Coupled; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D018698:Glutamic Acid; C023427:guanosine 5'-O-(2-thiodiphosphate); D002118:Calcium