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

11. Total Capacitance Percent Actual Capacitance= Soma Dendrite Soma

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

13. Percent Actual Capacitance vs. Dendrite Diameter

14. Percent Actual Capacitance vs. Length

15. Dual Compartments w/ Compartmentalized Cable
Dsoma=.004 cm
D2=.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-1 j
j+1 Ri Ri Rm Rm Rm

17. Percent Actual Capacitance vs. Dendrite Area
Soma
Dendrite

18. Percent Actual Capacitance vs. Soma Area
Dendrite
Soma

19. Percent Actual Capacitance vs. Cable Area
Dendrite
Soma

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

21. Percent Actual Capacitance vs. Dendrite Area
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