Hi !
I am trying to model the behaviour of squid giant axon at different temperature and using the results of this paper as a basis. (http://www.ncbi.nlm.nih.gov/pubmed/11081712). It reports the value of ~57mV at 5 oC and about -59 mV at 15oC. These values are different (more positive) than the standard values in HH model (-65 mV). Using the techniques mentioned in the forum and the ones mentioned in the NEURON book (Chapter 8, page 196), I initialize my model using a resting membrane potential of -57mV at 5oC. However, at those values, on injecting stimulating current, I get spontaneous activity. I am not sure if the values reported in the paper are correct (and should be strictly adhered to) or do I need to change the HH model (gnabar and gkabar) to elicit an action potential without spontaneous activity.
Thanks,
Mohit
Resting Membrane Potential
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Re: Resting Membrane Potential
The HH model is based on one particular set of experimental observations by one particular set of experimenters.
Rosenthal and Bezanilla did not perform the experiments that would be necessary to determine channel densities or the dynamics of gating in the animals that they studied, so you're left with a big puzzle.
Temperature affects many things, including not only channel gating but also gene expression and the activity of many enzymes etc. (not to mention ion transport mechanisms). Seasonal variations are bound to involve not only primary effects of temperature changes but also effects of any variations in salinity, and there could be lots of compensatory changes as well. For example, Rosenthal and Bezanilla attributed some of the changes they saw to seasonal alterations of cytoplasmic resistivity, which is definitely not one of the "temperature-sensitive factors" in the HH model.
For these reasons, comparisons between seasonally adapted axons may not be relevant if your primary interests are in the effects of acute temperature changes. For the latter, you'd really want to have a good empirical description of acute temperature effects on channel gating in squid axon. Surely someone somewhere did the relevant experiments and published their results? PubMed search for
squid axon temperature effects
finds 74 hits, of which a few might be relevant.
Rosenthal and Bezanilla did not perform the experiments that would be necessary to determine channel densities or the dynamics of gating in the animals that they studied, so you're left with a big puzzle.
Temperature affects many things, including not only channel gating but also gene expression and the activity of many enzymes etc. (not to mention ion transport mechanisms). Seasonal variations are bound to involve not only primary effects of temperature changes but also effects of any variations in salinity, and there could be lots of compensatory changes as well. For example, Rosenthal and Bezanilla attributed some of the changes they saw to seasonal alterations of cytoplasmic resistivity, which is definitely not one of the "temperature-sensitive factors" in the HH model.
For these reasons, comparisons between seasonally adapted axons may not be relevant if your primary interests are in the effects of acute temperature changes. For the latter, you'd really want to have a good empirical description of acute temperature effects on channel gating in squid axon. Surely someone somewhere did the relevant experiments and published their results? PubMed search for
squid axon temperature effects
finds 74 hits, of which a few might be relevant.
Re: Resting Membrane Potential
Thanks a lot for the reply.
Mohit
Mohit