Simulations of motor unit discharge patterns (Powers et al. 2011)

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Accession:143671
" ... To estimate the potential contributions of PIC (Persistent Inward Current) activation and synaptic input patterns to motor unit discharge patterns, we examined the responses of a set of cable motoneuron models to different patterns of excitatory and inhibitory inputs. The models were first tuned to approximate the current- and voltage-clamp responses of low- and medium-threshold spinal motoneurons studied in decerebrate cats and then driven with different patterns of excitatory and inhibitory inputs. The responses of the models to excitatory inputs reproduced a number of features of human motor unit discharge. However, the pattern of rate modulation was strongly influenced by the temporal and spatial pattern of concurrent inhibitory inputs. Thus, even though PIC activation is likely to exert a strong influence on firing rate modulation, PIC activation in combination with different patterns of excitatory and inhibitory synaptic inputs can produce a wide variety of motor unit discharge patterns."
Reference:
1 . Powers RK, Elbasiouny SM, Rymer WZ, Heckman CJ (2012) Contribution of intrinsic properties and synaptic inputs to motoneuron discharge patterns: a simulation study. J Neurophysiol 107:808-23 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Spinal cord lumbar motor neuron alpha ACh cell;
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns; Bursting; Action Potentials;
Implementer(s): Powers, Randy [rkpowers at u.washington.edu];
Search NeuronDB for information about:  Spinal cord lumbar motor neuron alpha ACh cell;
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PowersEtAl2012
code
Gfluctdv.mod *
ghchan.mod *
kca2.mod *
kdrRL.mod *
L_Ca.mod *
mAHP.mod *
na3rp.mod *
naps.mod *
synss.mod
ana_FI.hoc
ana_G.hoc
ana_passive.hoc
ana_vc.hoc
ana_vc_synss.hoc
AP_AHP.ses
FIgraph.hoc
FRcablepas.hoc
FRmnrampcc.ses
FRmnrampvc_synss.ses
FRMotoneuronNaHH.hoc
gramp.ses
GUI_FR_analysis.hoc
inhibdist
makebiramp.hoc *
passive.ses
RecActive.hoc
re-init.hoc
SetConductances.hoc
test.hoc
twobirampsdel.hoc *
vramp
vrampdel
vrampdel.hoc
                            
/****************************************************************
 * FILE ana_G.hoc
 *
 * init.hoc loads Randy's FR motoneuron and voltage ramp code
 * To execute, execute runvc("<modelname>")
 * This will save the current and voltage data, for the trace, one point 
 * per second, with the model name incorporated in the file name
 ****************************************************************/

objref vecV, vecI, ff
strdef fn, ldfl, myf

/**************************************************
 * PROC ana_G() begin
 *
 * Generate a conductance ramp and record the current and voltage
 * Argument is the cell file name
 **************************************************/

proc ana_G() {
    
    print "conductance clamp not yet implemented\n"
    return
    if (numarg() < 1) {
	print "ana_FI(): call with FR cell for argument"
	return
    }
    
    fn = $s1
    
    if (! xopen(fn)) {
	printf("Fail to open requested cell file %s\n", fn)
	return
    }
    
    sprint(myf, "%s/vramp", codeloc)
    load_file(myf)
    sprint(myf, "%s/FRmnrampvc.ses", codeloc)
    load_file(myf)
    //V0=-70
    
    //    SLOPE=.006
    // TR=10000
    simple()
    vrampon()
    
    rungc(fn)
    
}
// PROC ana_FI end

// PROC rungc() begin
// To execute, execute runvc("<modelname>")
// This will save the current and voltage data, for the trace, one point 
// per second, with the model name incorporated in the file name

proc rungc() {local i
    ldfl = $s1
    fo=load_file(ldfl)
    if (!fo) {
	printf("bad file\n")
	return
    }
    
    objref vecV, vecI, ff
    vecI=new Vector()
    vecI.record(&VClamp[0].i)
    vecV = new Vector()
    vecV.record(&v(0.5))
    init()
    run()
    ff = new File()
//    sprint(filename,"%s-vc_V0=%d_SLOPE=%.3f_TR=%d.csv",fn,V0,SLOPE,TR)
    sprint(fn, "FRvcdata_%s.csv", ldfl)
    fo=ff.wopen(fn)
    if (!fo) {
	printf("Fail to open file %s, code=%d\n", fn, fo)
	return
    }
    ff.printf("label:%s\n", ldfl)
    ff.printf("%d\n", (vecI.size-1)/40)
    // We only need to save one point per millicsecond, i.e. every 40th point
    for (i=0; i<vecI.size; i=i+40) {
	ff.printf("%.4f,%.5f\n", vecV.x[i], vecI.x[i])
    }
    ff.close()
    
    printf("Created output file %s\nUse Excel to analyze IV curve and PIC parameters", fn)
    
}
// PROC rungc end

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