Work

The Concentration of Synaptically Released Glutamate Outside of the Climbing Fiber–Purkinje Cell Synaptic Cleft

Year: 1999

Type: article

Abstract: AMPA receptors and glutamate transporters expressed by cerebellar Bergmann glial cells are activated by neurotransmitter released from climbing fibers (). Based on anatomical evidence, this is most likely the result of glutamate diffusing out of the climbing fiber-Purkinje cell synaptic clefts (). We used the change in the EC50 of the Bergmann glia AMPA receptors produced by cyclothiazide (CTZ) to estimate the concentration of glutamate reached at the glial membrane. The decrease of the EC50 gives rise to a concentration-dependent potentiation of the AMPA receptor-mediated responses (). By comparing the increase in amplitude of the AMPA receptor response in the Bergmann glia (840 +/- 240%; n = 8) with the shift in the glutamate dose-response curve measured in excised patches (EC50, 1810 microM in control vs 304 microM in CTZ), we estimate that the extrasynaptic transmitter concentration reaches 160-190 microM. This contrasts with the concentration in the synaptic cleft, thought to rapidly rise above 1 mM, but is still high enough to activate glutamate receptors. These results indicate that the sphere of influence of synaptically released glutamate can extend beyond the synaptic cleft.

Source: Journal of Neuroscience

DOI: 10.1523/jneurosci.19-13-05265.1999

Authors: Jeffrey A. Dzubay, Craig E. Jahr

Institutions: Oregon Health & Science University, Vollum Institute

Language: English

Topic: Neuroscience and Neuropharmacology Research

Subfield: Cellular and Molecular Neuroscience

Field: Neuroscience

Domain: Life Sciences

Open Access status: hybrid

Funders: National Institutes of Health, National Institute of Mental Health, National Institute of Neurological Disorders and Stroke

Awards: SPONTANEOUS NMDA CHANNEL ACTIVITY IN HIPPOCAMPAL SLICES, Electrophysiological analysis of neurotransmission