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Modulation of synaptic transmission at CA1 pyramidal neuron–O-LM interneuron synapses is primarily controlled by axonal Kv1 channels.

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posted on 2014-11-19, 17:35 authored by Sooyun Kim

(A) Block of Kv1 channels enhances transmission. Top, unitary EPSCs at CA1 PN–O-LM IN synapses evoked by single presynaptic APs in control conditions and in the presence of 100 nM α-DTX. Traces represent averages from 10 single sweeps. Bottom, summary bar graph of the effects of α-DTX on EPSC peak amplitude. Note that α-DTX markedly increased synaptic efficacy. (B) Block of Kv1 channels reduces facilitation of transmission. Top, EPSCs at CA1 PN–O-LM IN synapses evoked by trains of five presynaptic APs in control conditions (left) and in the presence of 100 nM α-DTX (right). Bottom, facilitation ratio (EPSCn/EPSC1), plotted against stimulus number, in control conditions (squares) and in the presence of α-DTX (circles). Somatic holding potential –60 mV. (C) Block of Kv1 channels abolishes static analog modulation of transmission. Top, unitary EPSCs at CA1 PN–O-LM IN synapses evoked by single presynaptic APs in control conditions and in the presence of 100 nM α-DTX. Presynaptic membrane potential were held at –60 mV (left; same recording as in (A)), and –50 mV (right). Bottom, summary bar graph of the effects of α-DTX on EPSC peak amplitude (EPSCDTX/EPSCControl) for two different presynaptic holding potential (black, –60 mV; red, –50 mV). Note that α-DTX occluded the effects of changing membrane potential in the presynaptic neuron. (D) Block of Kv1 channels broadens the axonal AP. Top, axonal AP traces in control conditions and in the presence of 100 nM α-DTX. Bottom, summary bar graph showing the effects of α-DTX on half-duration of somatic and axonal AP. Axonal recording site is 264 µm from the soma. Note that α-DTX selectively increased axonal AP duration. (E) Block of Kv1 channels reduces activity-dependent AP broadening. Top, superposition of 1st, 5th, and 50th axonal AP in control conditions (left) and in the presence of 100 nM α-DTX (right). Bottom, plot of axonal AP half-width against stimulus number in control conditions (squares) and in the presence of 100 nM α-DTX (circles). Somatic holding potential –60 mV. Data from 7 recordings at distances of 200 to 500 µm. Axonal recording site is 264 µm from the soma. (F) Block of Kv1 channels reduces static AP broadening. Top, superposition of axonal APs in control conditions and in the presence of 100 nM α-DTX at –60 mV (left; same recording as in (D)), and –50 mV (right). Bottom, summary bar graph of the effects of α-DTX on AP broadening at –60 mV (black) and –50 mV (red). Note that the depolarization-induced AP broadening reduced the effect of α-DTX. Axonal recording site is 264 µm from the soma. Bars indicate mean ± SEM. Open circles represent data from individual experiments. Data from the same experiment or for the same experimental conditions were connected by lines. *0.01≤P<0.05.

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