A dual-Ca2+-sensor model for neurotransmitter release in a central synapse (Sun et al. 2007)

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Accession:105506
"Ca2+-triggered synchronous neurotransmitter release is well described, but asynchronous release-in fact, its very existence-remains enigmatic. Here we report a quantitative description of asynchronous neurotransmitter release in calyx-of-Held synapses. ... Our results reveal that release triggered in wild-type synapses at low Ca2+ concentrations is physiologically asynchronous, and that asynchronous release completely empties the readily releasable pool of vesicles during sustained elevations of Ca2+. We propose a dual-Ca2+-sensor model of release that quantitatively describes the contributions of synchronous and asynchronous release under conditions of different presynaptic Ca2+ dynamics."
Reference:
1 . Sun J, Pang ZP, Qin D, Fahim AT, Adachi R, S├╝dhof TC (2007) A dual-Ca2+-sensor model for neurotransmitter release in a central synapse. Nature 450:676-82 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Synapse;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: IGOR Pro;
Model Concept(s): Calcium dynamics;
Implementer(s):
/
Dual_sensor_model_code
readme.txt
Dual_sensor_model_code.txt
                            
Macro Dual_sensor_model_OK()
Variable i=0,n=6000,Ca,alpha,beta,delta,gama,rou,dT=0.02*10^(-3),j=1,b,base,gama2
Variable  X_th=3000		//RRP
String/G SW
PauseUpdate;  
Silent 1
Make/O/N=6000 X_Ca1, X_Ca2, X_Ca3, X_Ca4, X_Ca5, XX_Ca5, syt2=0, X_Time, Fuse=0, Fused=0, peakrate=0, peak_delay=0, Ca_i=0, Y_Ca1, Y_Ca2, yALPHA, yBETA

Yalpha=2.94e+06
Ybeta=130
alpha=1.53e+08			//set to 0 in KO
beta=5800			//set to 0 in KO

gama=6000
gama2=6000
b=0.25

Ca=0
do
	syt2=X_th
	X_Ca1[0]=0
	X_Ca2[0]=0
	X_Ca3[0]=0
	X_Ca4[0]=0
	X_Ca5[0]=0
	XX_Ca5[0]=0
	X_Time[0]=0

	i=0
	do
		i+=1
		if (i>1000)
			Ca=(j)*0.01*10^(-6)
			if (j>10)
				Ca=(j-10)*0.1*10^(-6)
			endif
			if (j>20)
				Ca=(j-20)*1*10^(-6)
			endif

//ca=waveform_ca[i]		//for single photolysis trace fitting

		else
			Ca=0
		endif
		X_Time[i]=i*dT
X_Ca1[i]=X_Ca1[i-1]+dT*(Ca*5*alpha*syt2[i-1]-beta*X_Ca1[i-1]+2*beta*b*X_Ca2[i-1]-Ca*4*alpha*X_Ca1[i-1])
X_Ca2[i]=X_Ca2[i-1]+dT*(Ca*4*alpha*X_Ca1[i-1]-2*beta*b*X_Ca2[i-1]+3*beta*b^2*X_Ca3[i-1]-Ca*3*alpha*X_Ca2[i-1])
X_Ca3[i]=X_Ca3[i-1]+dT*(Ca*3*alpha*X_Ca2[i-1]-3*beta*b^2*X_Ca3[i-1]+4*beta*b^3*X_Ca4[i-1]-Ca*2*alpha*X_Ca3[i-1])
X_Ca4[i]=X_Ca4[i-1]+dT*(Ca*2*alpha*X_Ca3[i-1]-4*beta*b^3*X_Ca4[i-1]+5*beta*b^4*X_Ca5[i-1]-Ca*1*alpha*X_Ca4[i-1])
		X_Ca5[i]=X_Ca5[i-1]+dT*(Ca*1*alpha*X_Ca4[i-1]-5*beta*b^4*X_Ca5[i-1]-gama*X_Ca5[i-1])
Y_Ca1[i]=Y_Ca1[i-1]+dT*(Ca*2*Yalpha*syt2[i-1]-Ybeta*Y_Ca1[i-1]+2*Ybeta*b*Y_Ca2[i-1]-Ca*4*Yalpha*Y_Ca1[i-1])
		Y_Ca2[i]=Y_Ca2[i-1]+dT*(Ca*1*Yalpha*Y_Ca1[i-1]-2*Ybeta*b*Y_Ca2[i-1]-gama2*Y_Ca2[i-1])
syt2[i]=syt2[i-1]+dT*(beta*X_Ca1[i-1]-5*alpha*syt2[i-1]*Ca+Ybeta*Y_Ca1[i-1]-2*Yalpha*syt2[i-1]*Ca)-dT*0.2*10^(-3)*syt2[i-1]
//		Fuse[i]=(2.23*10^(-3)*syt2[i-1]+gama*X_Ca5[i-1]+gama2*Y_Ca2[i-1])*dT	//for KO
		Fuse[i]=(0.417*10^(-3)*syt2[i-1]+gama*X_Ca5[i-1]+gama2*Y_Ca2[i-1])*dT	//for WT
		Fused[i]=Fused[i-1]+Fuse[i]
		Fuse[i]*=0.001/dT
	while(i<6000)
	wavestats/q fuse
	peakrate[j]=V_max
	peak_delay[j]=(V_maxloc-1000)*dT*1000
	Ca_i[j]=Ca*1e6
	print j
	j+=1
while(j<40)	
end

	

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