Editors' ChoiceNeurobiology

A Highly Sensitive Trigger

STKE  15 Aug 2000:
Vol. 2000, Issue 45, pp. tw5
DOI: 10.1126/stke.2000.45.tw5

Neurotransmitter release from vesicles in the presynaptic terminal is triggered by a brief increase in calcium that is triggered by an action potential. There has been a long debate concerning the sensitivity of the vesicular calcium sensor for mammalian central synapses and the minimal calcium concentration that is necessary to start the subsequent molecular events that lead to vesicle fusion with the plasma membrane. Bollmann et al. measured laser-induced release of caged calcium in a rat auditory brainstem synapse and found that increases in calcium concentrations of 1 µM evoked release. The authors' analysis indicates that a brief spike of 10 µM calcium would be sufficient to match the rate of synaptically evoked neurotransmitter release. This result implies that the calcium sensor in the presynaptic terminal has a high calcium affinity.

Bollman, J.H., Sakmann, B., and Borst, J.G.G. (2000) Calcium sensitivity of glutamate release in a calyx-type terminal. Science 289: 953-957. [Abstract] [Full Text]