@article{3492, 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.}, author = {Geiger, Jörg and Jonas, Peter M}, issn = {0896-6273}, journal = {Neuron}, number = {3}, pages = {927 -- 939}, publisher = {Elsevier}, title = {{Dynamic control of presynaptic Ca(2+) inflow by fast-inactivating K+ channels in hippocampal mossy fiber boutons}}, doi = {10.1016/S0896-6273(00)00164-1}, volume = {28}, year = {2000}, }