title: Purinergic transmission and transglial signaling between neuron somata in the dorsal root ganglion.
abstract: Most dorsal root ganglion neuronal somata (NS) are isolated from their neighbours by a satellite glial cell (SGC) sheath. However, some NS are associated in pairs, separated solely by the membrane septum of a common SGC to form a neuron-glial cell-neuron (NGlN) trimer. We reported that stimulation of one NS evokes a delayed, noisy and long-duration inward current in both itself and its passive partner that was blocked by suramin, a general purinergic antagonist. Here we test the hypothesis that NGlN transmission involves purinergic activation of the SGC. Stimulation of the NS triggered a sustained current noise in the SGC. Block of transmission through the NGlN by reactive blue 2 or thapsigargin, a Ca(2+)  store-depletion agent, implicated a Ca(2+)  store discharge-linked P2Y receptor. P2Y2 was identified by simulation of the NGlN-like transmission by puffing UTP onto the SGC and by immunocytochemical localization to the SGC membrane septum. Block of the UTP effect by BAPTA, an intracellular Ca(2+)  scavenger, supported the involvement of SGC Ca(2+)  stores in the signaling pathway. We infer that transmission through the NGlN trimer involves secretion of ATP from the NS and triggering of SGC Ca(2+)  store discharge via P2Y2 receptors. Presumably, cytoplasmic Ca(2+)  elevation leads to the release of an as-yet unidentified second transmitter from the glial cell to complete transmission. Thus, the two NS of the NGlN trimer communicate via a 'sandwich synapse' transglial pathway, a novel signaling mechanism that may contribute to information transfer in other regions of the nervous system.
authors.affiliation: Laboratory of Synaptic Transmission, Toronto Western Research Institute, Toronto, Ontario, Canada.
authors.forename: Gabriela M
authors.initials: GM
authors.lastname: Rozanski
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.forename: Hyunhee
authors.initials: H
authors.lastname: Kim
authors.forename: Elise F
authors.initials: EF
authors.lastname: Stanley
mesh_terms: D000200:Action Potentials; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002642:Chick Embryo; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009457:Neuroglia / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D058913:Purinergic Agonists / Q000494:pharmacology; D058473:Receptors, Purinergic P2Y2 / Q000378:metabolism*; D013498:Suramin / Q000494:pharmacology; D009435:Synaptic Transmission
chemical_list: D058913:Purinergic Agonists; D058473:Receptors, Purinergic P2Y2; D013498:Suramin; D000255:Adenosine Triphosphate; D002118:Calcium