Presynaptic Ca2+ buffers control the strength of a fast post-tetanic hyperpolarization mediated by the alpha3 Na(+)/K(+)-ATPase.
The excitability of CNS presynaptic terminals after a tetanic burst of action potentials is important for synaptic plasticity. The mechanisms that regulate excitability, however, are not well understood. Using direct recordings from the rat calyx of Held terminal, we found that a fast Na(+)/K(+)-ATPase (NKA)-mediated post-tetanic hyperpolarization (PTH) controls the probability and precision of subsequent firing. Notably, increasing the concentration of internal Ca(2+) buffers or decreasing Ca(2+) influx led to larger PTH amplitudes, indicating that an increase in [Ca(2+)](i) regulates PTH via inhibition of NKAs. The characterization for the first time of a presynaptic NKA pump current, combined with immunofluorescence staining, identified the alpha3-NKA isoform on calyx terminals. Accordingly, the increased ability of the calyx to faithfully fire during a high-frequency train as it matures is paralleled by a larger expression of alpha3-NKA during development. We propose that this newly discovered Ca(2+) dependence of PTH is important in the post-burst excitability of nerve terminals.
Kim
Jun Hee
JH
The Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, USA.
Sizov
Igor
I
Dobretsov
Maxim
M
von Gersdorff
Henrique
H
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism* / Q000648:ultrastructure; D002021:Buffers; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012249:Rhombencephalon / Q000378:metabolism* / Q000648:ultrastructure; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D002021:Buffers; D021122:Protein Subunits; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium