Regensburg 2016 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 38: Neurosciences

BP 38.3: Vortrag

Mittwoch, 9. März 2016, 10:30–10:45, H45

Single-channel current of calcium channels in rat neocortical layer 5 pyramidal neurons at physiological calcium concentration: fluctuation analysis with voltage ramps — •Christian Scheppach^1,2 and Hugh P.C. Robinson¹ — ¹Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, U.K. — ²Institute of Physics, University of Freiburg, Freiburg, Germany

Voltage-gated Ca²⁺ channels are present in many neuronal membranes, playing important roles in presynaptic transmitter release, and in postsynaptic integration of inputs, e.g. by dendritic Ca²⁺ action potentials. Their single-channel current in physiological extracellular Ca²⁺ concentrations (1-2 mM) is not well known, and is too small to be resolved directly with standard patch-clamp. Yet it is a key parameter e.g. for stochastic effects arising from the random opening and closing of single Ca²⁺ channels. We recorded Ca²⁺ channel currents from neocortical L5 pyramidal neurons and used fluctuation analysis to obtain a single-channel current of 0.07 pA at −25 mV membrane voltage and 2 mM extracellular Ca²⁺. A novel fluctuation analysis protocol was developed, whereby channel currents are recorded during voltage ramps. The presented technique is robust with respect to unstable experimental conditions like rapid run-down of the channel current. The data on the single Ca²⁺ channel current are relevant to a quantitative understanding of dendritic Ca²⁺ action potentials, especially their stochastic aspects.

Reference: C. Scheppach, H.P.C. Robinson (in preparation).