Calcium sensitivity of glutamate release in a calyx-type terminal.
Synaptic efficacy critically depends on the presynaptic intracellular calcium concentration ([Ca2+]i). We measured the calcium sensitivity of glutamate release in a rat auditory brainstem synapse by laser photolysis of caged calcium. A rise in [Ca2+]i to 1 micromolar readily evoked release. An increase to >30 micromolar depleted the releasable vesicle pool in <0.5 millisecond. A comparison with action potential-evoked release suggested that a brief increase of [Ca2+]i to approximately 10 micromolar would be sufficient to reproduce the physiological release pattern. Thus, the calcium sensitivity of release at this synapse is high, and the distinction between phasic and delayed release is less pronounced than previously thought.
Max-Planck-Institute for Medical Research, Department of Cell Physiology, Jahnstrasse 29, D-69120 Heidelberg, Germany. jbollman@mpimf-heidelberg.mpg.de
J H
JH
Bollmann
B
B
Sakmann
J G
JG
Borst
D000200:Action Potentials; D000818:Animals; D001933:Brain Stem / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D019706:Excitatory Postsynaptic Potentials; D018698:Glutamic Acid / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010782:Photolysis; D017729:Presynaptic Terminals / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000378:metabolism
D018698:Glutamic Acid; D002118:Calcium