Tonic activation of NMDA receptors by ambient glutamate of non‐synaptic origin in the rat hippocampus

摘要: In several neuronal types of the CNS, glutamate and GABA receptors mediate a persistent current which reflects presence low concentration transmitters in extracellular space. Here, we further characterize tonic mediated by ambient rat hippocampal slices. A small amplitude (53.99 +/- 6.48 pA at +40 mV) with voltage dependency pharmacology NMDA (NMDARs) was detected virtually all pyramidal cells CA1 subiculum areas. Manipulations aiming increasing D-serine or glycine concentrations failed to modify this indicating that binding sites NMDARs mediating were saturated. contrast, non-transportable inhibitors transporters increased current, primarily regulates its magnitude. Neither AMPA/kainate nor metabotropic contributed significantly excitation neurons. transporter inhibitors, however, significant proportion conductance AMPA receptors. The unaffected when inhibiting vesicular release from neurons but upon inhibition enzyme converting glutamine glial cells. These observations indicate is mainly origin. Finally, experiments use-dependent antagonist MK801 indicated are probably extra-synaptic NMDARs.