Dynamic control of presynaptic Ca(2+) inflow by fast-inactivating K+ channels in hippocampal mossy fiber boutons Journal Article


Author(s): Geiger, Jörg R; Jonas, Peter
Article Title: Dynamic control of presynaptic Ca(2+) inflow by fast-inactivating K+ channels in hippocampal mossy fiber boutons
Affiliation
Abstract: Analysis of presynaptic determinants of synaptic strength has been difficult at cortical synapses, mainly due to the lack of direct access to presynaptic elements. Here we report patch-clamp recordings from mossy fiber boutons (MFBs) in rat hippocampal slices. The presynaptic action potential is very short during low-frequency stimulation but is prolonged up to 3-fold during high-frequency stimulation. Voltage-gated K+ channels in MFBs inactivate rapidly but recover from inactivation very slowly, suggesting that cumulative K+ channel inactivation mediates activity-dependent spike broadening. Prolongation of the presynaptic voltage waveform leads to an increase in the number of Ca2+ ions entering the terminal per action potential and to a consecutive potentiation of evoked excitatory postsynaptic currents at MFB-CA3 pyramidal cell synapses. Thus, inactivation of presynaptic K+ channels contributes to the control of efficacy of a glutamatergic synapse in the cortex.
Keywords: Animals; Rats; Calcium; Electric Stimulation; Synaptic Transmission; Patch-Clamp Techniques; Rats, Wistar; Action Potentials; Excitatory Postsynaptic Potentials; Ion Channel Gating; Potassium Channels; Elapid Venoms; Potassium Channel Blockers; Tetraethylammonium; Glutamic Acid; Reaction Time; Presynaptic Terminals; Tetrodotoxin; Mossy Fibers, Hippocampal
Journal Title: Neuron
Volume: 28
Issue 3
ISSN: 0896-6273
Publisher: Elsevier  
Date Published: 2000-12-01
Start Page: 927
End Page: 939
DOI: 10.1016/S0896-6273(00)00164-1
Open access: no