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111 lines
3.1 KiB
111 lines
3.1 KiB
TITLE kht.mod The high threshold conductance of cochlear nucleus neurons |
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COMMENT |
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NEURON implementation of Jason Rothman's measurements of VCN conductances. |
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This file implements the high threshold potassium current found in several brainstem |
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nuclei of the auditory system, including the spherical and globular bushy cells |
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(Manis and Marx, 1991; Rothman and Manis, 2003a,b) and multipolar (stellate) |
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cells of the ventral cochlear nucleus, principal cells of the medial |
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nucleus of the trapzoid body (Brew and Forsythe, 1995, Wang and Kaczmarek, |
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1997) and neurons of the medial superior olive. The current is likely mediated by |
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Kv3.1 potassium channel subunits. The specific |
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implementation is described in Rothman and Manis, J. Neurophysiol. 2003, in the |
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appendix. Measurements were made from isolated neurons from adult guinea pig, |
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under reasonably stringent voltage clamp conditions. The measured current is |
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sensitive to 4-aminopyridine and TEA, but is spared by mamba snake toxi |
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dendrotoxin I. |
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Similar conductrances are found in the homologous neurons of the avian auditory |
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system (Reyes and Rubel; Zhang and Trussell; Rathouz and Trussell), and the |
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conductance described here, in the absence of more detailed kinetic measurements |
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, is probably suitable for use in modeling that system. |
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Original implementation by Paul B. Manis, April (JHU) and Sept, (UNC)1999. |
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File split implementation, February 28, 2004. |
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Contact: pmanis@med.unc.edu |
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ENDCOMMENT |
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UNITS { |
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(mA) = (milliamp) |
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(mV) = (millivolt) |
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(nA) = (nanoamp) |
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} |
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NEURON { |
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THREADSAFE |
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SUFFIX kht |
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USEION k READ ek WRITE ik |
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RANGE gbar, gkht, ik, q10g |
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GLOBAL ninf, pinf, ntau, ptau |
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} |
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:INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} |
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ASSIGNED { |
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celsius (degC) : model is defined on measurements made at room temp in Baltimore: 22 degC |
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ik (mA/cm2) |
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ek (mV) |
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gkht (mho/cm2) |
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pinf ninf |
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ptau (ms) |
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ntau (ms) |
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qg () : computed q10 for gnabar based on q10g |
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q10 () |
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} |
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PARAMETER { |
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v (mV) |
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dt (ms) |
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gbar = 0.01592 (mho/cm2) <0,1e9> |
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nf = 0.85 <0,1> :proportion of n vs p kinetics |
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q10tau = 3.0 |
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q10g = 2.0 |
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} |
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STATE { |
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n p |
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} |
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LOCAL nexp, pexp |
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BREAKPOINT { |
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SOLVE states METHOD cnexp |
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gkht = qg*gbar*(nf*(n^2) + (1-nf)*p) |
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ik = gkht*(v - ek) |
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} |
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INITIAL { |
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qg = q10g^((celsius-22)/10 (degC)) |
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q10 = q10tau^((celsius - 22)/10 (degC)) |
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rates(v) |
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p = pinf |
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n = ninf |
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} |
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DERIVATIVE states { :Computes state variables m, h, and n |
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rates(v) : at the current v and dt. |
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n' = (ninf - n)/ntau |
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p' = (pinf - p)/ptau |
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} |
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PROCEDURE rates(v (mV)) { :Computes rate and other constants at current v. |
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:Call once from HOC to initialize inf at resting v. |
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ninf = (1 + exp(-(v + 15) / 5 (mV)))^-0.5 |
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pinf = 1 / (1 + exp(-(v + 23) / 6 (mV))) |
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ntau = (100 (ms)/ (11*exp((v+60) / 24 (mV)) + 21*exp(-(v+60) / 23 (mV)))) + 0.7 |
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ntau = ntau/q10 |
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ptau = (100 (ms)/ (4*exp((v+60) / 32 (mV)) + 5*exp(-(v+60) / 22 (mV)))) + 5 |
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ptau = ptau/q10 |
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} |
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