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

 Download zip file   Auto-launch 
Help downloading and running models
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(3):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 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 cell;
/
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
                            
 COMMENT
 
 kca2.mod
 
 Calcium-dependent potassium channel
 Based on
 Pennefather (1990) -- sympathetic ganglion cells
 taken from
 Reuveni et al (1993) -- neocortical cells
 
 Author: Zach Mainen, Salk Institute, 1995, zach@salk.edu
 modified Jan,2000 by RKP;modified July 2005 to include a contribution from calcium
flowing through L channels
 	
 ENDCOMMENT

 NEURON {
 	SUFFIX kca2
 	USEION k READ ek WRITE ik
 	USEION ca READ ica WRITE cai
  USEION caL READ icaL 	
  RANGE n, g,ik,cai,ica,icaL,depth1,taur1,depth2,taur2
 	GLOBAL Ra, Rb, caix
 }
 
 UNITS {
 	(mA) = (milliamp)
 	(mV) = (millivolt)
 	(S) = (siemens)
 	(um) = (micron)
 	(molar) = (1/liter)			: moles do not appear in units
 	(mM)	= (millimolar)
 	(msM)	= (ms mM)
 	FARADAY = (faraday) (coulomb)
 } 
 
 PARAMETER {
 	g = 0.03   	(S/cm2)	
 	v 		(mV)
 	cai  		(mM)
 	caix = 2	
  cainf=0.0001
 	depth1	= .1	(um)		: depth of shell
 	taur1	= 20	(ms)		: rate of calcium removal
 	depth2	= 10	(um)		: depth of shell
 	taur2	= 200	(ms)		: rate of calcium removal
								
  Ra   = 0.1		: max act rate  
 	Rb   = 0.1		: max deact rate 
 
 	celsius		(degC)
 } 
 
 
 ASSIGNED {
 	ik 		(mA/cm2)
	 ica (mA/cm2)
 	icaL (mA/cm2)
 	ek		(mV)
 	ninf
 	ntau 		(ms)	
  drive_channel1	(mM/ms)
  drive_channel2	(mM/ms)
 }
  
 
 STATE { 
 n 
 ca (mM)
	caL (mM)
}
 
 INITIAL { 
	ca=cainf
 caL=0
 cai=cainf
 rates(cai)
 	n = ninf
 }
 
 BREAKPOINT {
         SOLVE states METHOD cnexp
 	ik =  g *n* (v - ek)
 } 
 

DERIVATIVE states {  
 	drive_channel1 =  - (10000) * ica/ (2 * FARADAY * depth1)
 	if (drive_channel1 <= 0.) { drive_channel1 = 0. }	: cannot pump inward
 	ca' = drive_channel1 + (cainf-ca)/taur1
 	drive_channel2 =  - (10000) * icaL/ (2 * FARADAY * depth2)
 	if (drive_channel2 <= 0.) { drive_channel2 = 0. }	: cannot pump inward
 	caL' = drive_channel2 + (cainf-caL)/taur2
 	cai = ca + caL

          rates(cai)    
         n' = (ninf-n)/ntau
}
PROCEDURE rates(cai(mM)) {  LOCAL a,b
							UNITSOFF
         a = Ra * (1e3*(cai  -cainf))^caix		: rate constant depends on cai in uM
         b = Rb
         ntau = 1/(a+b)
        	ninf = a*ntau
					UNITSON
 }

Loading data, please wait...