Characterization of a synaptiform transmission between a neuron and a glial cell in the leech central nervous system.
The cross-talk between neurons and glial cells is receiving increased attention because of its potential role in information processing in nervous systems. Stimulation of a single identifiable neuron, the neurosecretory Leydig interneuron in segmental ganglia of the leech Hirudo medicinalis, which modulates specific behaviors in the leech, evokes membrane hyperpolarization directly in the giant glial cell (Schmidt and Deitmer. Eur J Neurosci 11:3125-3133, 1999). We have studied the neuron-to-glia signal transmission in the voltage-clamped giant glial cell to determine whether this interaction exhibits properties of a chemical synapse. The glial response had a mean latency of 4.9 s and was dependent on the action potential frequency; the glial cell responded to as few as five Leydig neuron action potentials in 50% of the trials. The glial current was sustained for minutes during repetitive Leydig neuron activity without any sign of desensitization. The current was sensitive to tetraethylammonium, and its reversal potential of -78 mV shifted with the external K+ concentration. The glial response increased with the duration of the neuronal action potentials and was sensitive to the external Ca2+/Mg2+ concentration ratio. The results suggest that Leydig neuron activity leads to a Ca2+-dependent release of transmitter from the neuronal dendrites, evoking an K+ outward current in the giant glial cell, implying a synapse-like transmission between a neuron and a glial cell.
Britz
Frank C
FC
Abteilung für Allgemeine Zoologie, FB Biologie, Universität Kaiserslautern, Germany.
Lohr
Christian
C
Schmidt
Joachim
J
Deitmer
Joachim W
JW
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002490:Central Nervous System / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D003712:Dendrites / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007395:Interneurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007865:Leeches / Q000166:cytology / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009490:Neurosecretory Systems / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology
D015221:Potassium Channels; D019789:Tetraethylammonium; D008274:Magnesium; D002118:Calcium