Multiple climbing fibers signal to molecular layer interneurons exclusively via glutamate spillover.
Spillover of glutamate under physiological conditions has only been established as an adjunct to conventional synaptic transmission. Here we describe a pure spillover connection between the climbing fiber and molecular layer interneurons in the rat cerebellar cortex. We show that, instead of acting via conventional synapses, multiple climbing fibers activate AMPA- and NMDA-type glutamate receptors on interneurons exclusively via spillover. Spillover from the climbing fiber represents a form of glutamatergic volume transmission that could be triggered in a regionalized manner by experimentally observed synchronous climbing fiber activity. Climbing fibers are known to direct parallel fiber synaptic plasticity in interneurons, so one function of this spillover is likely to involve controlling synaptic plasticity.
Szapiro
Germán
G
Laboratoire de Neurobiologie, Ecole Normale Supérieure, CNRS, 46 rue d'Ulm, 75005 Paris, France.
Barbour
Boris
B
D000818:Animals; D000831:Animals, Newborn; D002531:Cerebellum / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D005971:Glutamates / Q000378:metabolism*; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009412:Nerve Fibers / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate