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The Measurement of Cell Capacitance in Multi-compartment Cells

The Measurement of Cell Capacitance in Multi-compartment Cells. Arif Patel Arlene Pineda Chris Khalil. Membrane Capacitance. Cell membranes have a capacitive property. Membrane capacitance (C m ) is related to cell surface area. C m plays a role in neuronal physiology. Hypothesis.

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The Measurement of Cell Capacitance in Multi-compartment Cells

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  1. The Measurement of Cell Capacitance in Multi-compartment Cells Arif Patel Arlene Pineda Chris Khalil

  2. Membrane Capacitance • Cell membranes have a capacitive property. • Membrane capacitance (Cm) is related to cell surface area. • Cm plays a role in neuronal physiology.

  3. Hypothesis • The Problem: Different methods for measuring Cm produce different results. • We propose that this difference is due to the complex anatomical structure of neurons.

  4. Methodology • Three experimental techniques for measuring Cm • Current Step Method (current clamp) • Voltage Step Method (voltage clamp) • Voltage Ramp Method (voltage clamp) • Three levels of modeling to compare the measurements • Experiments were performed in crab stomatogastric neurons.

  5. Current Step Method • When performed in an isopotential sphere

  6. Current Step Method • When performed in multi compartment cells

  7. Voltage Step Method

  8. Voltage Ramp Method

  9. Results of Experiments • Average Measured Capacitance for three methods: • Current Step (n=6): 23.68nF • Voltage Step (n=8): 2.87nF • Voltage Ramp (n=8):2.72nF Why are they different? Which is correct?

  10. Dendrite Soma Dendrite Soma Three Models • Dual compartment attached by a resistive cable • Compartmentalized cable with added membrane • Two cylinder with compartmentalized dendrite and cable • Assumptions for model simplification: • -Ri, Rm, Cm constant • -Vr=0

  11. Soma Dendrite Dendrite Soma Total Capacitance Percent Actual Capacitance=

  12. IAD IAS IRD IRS IRS IAD IAD IRD Current Representation

  13. Percent Actual Capacitance vs. Dendrite Diameter

  14. Percent Actual Capacitance vs. Length

  15. Dual Compartments w/ Compartmentalized Cable D2=.004 cm Dsoma=.004 cm Ri Ri Dendrite Soma j -1 j j +1 Rm Rm l=.06 cm Dcable=.001 cm

  16. Dual Compartments w/ Compartmentalized Cable Code j j-1 j+1 Ri Ri Rm Rm Rm

  17. Dendrite Soma Percent Actual Capacitance vs. Dendrite Area

  18. Soma Dendrite Percent Actual Capacitance vs. Soma Area

  19. Dendrite Soma Percent Actual Capacitance vs. Cable Area

  20. Two Cylinders w/ Compartment Cable & Dendrite Dsoma=.004 cm Soma j -1 j j +1 jd-1 jd j j jd+1 jd+1 jd+1 l=.06 cm Dcable=.001 cm Dendrite

  21. Percent Actual Capacitance vs. Dendrite Area Dendrite Soma

  22. Significance of Findings • The best method for measuring cm is the current step • Voltage curve can depicts two distinct processes • Independent of morphology

  23. Significance of Findings • Voltage Ramp method has provided better results than Voltage Step. • Voltage Step has provided the least reliable results • Not allowed to equalize in voltage clamp

  24. Special Thanks to.. • Professor Golowasch • Professor Nadim • Professor Bose • TA’s: • Shunbing Zhao • Lakshmi Chandrasekaran

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