A. Strassberg
Caltech
April 1992
(UnClamp.doc)

UnClamp Demo
- this GENESIS script simulates the response of a space-clamped
patch of squid giant axon membrane to a step current injection.
- the membrane consists of a population of Na and K channels
channels undergoing Markov kinetics with voltage-dependent
rate constants.  The Na and K channel population objects are
demonstrated.
- a step current injection is applied to the membrane and
the dynamics of this current injection I(t), the membrane voltage V(t),
the membrane currents INa(t) and IK(t), and the ionic conductances
gNa(t) and gK(t) are observed.

I. Installment
- the script for the UnClamp demo is contained within
five files:
                <sim_obj.g>
                <forms.g>
                <messages.g>
                <graphs.g>
                <UnClamp.g>

- running the script <UnClamp.g> will initiate the simulation

II. Units
                time            ms
                voltage         mV
                current         pA
                area            um2
                conductance     pS
                capacitance     pF
                density         channels/um^2

III. Simulation Operation
- for given membrane surface area, Na and K channel densities,
Na and K open channel conductances, membrane leakage conductance
per unit area, leakage voltage,  membrane capacitance per unit area,
initial injection current, step injection current,
time and duration of current step, the simulation computes the
dynamics of the membrane voltage based upon the standard lumped
parallel circuit model used in compartmental modeling (see
Strassberg and DeFelice, 1992, CNS Memo).  The response of the
membrane currents and conductances also can be observed.

IV. See Also

        NaChannel.doc
        KChannel.doc
        VClamp.doc
        ConClamp.doc
        ConVClamp.doc

        Strassberg and DeFelice, 1992, Neural Computation (submitted)
        Strassberg and DeFelice, 1992, CNS Memo

V.  Questions

        Please send any questions to
        strass@cns.caltech.edu
