Edelstein1996 - EPSP ACh event

Model of a nicotinic Excitatory Post-Synaptic Potential in a Torpedo electric organ. Acetylcholine is not represented explicitely, but by an event that changes the constants of transition from unliganded to liganded. 

This model has initially been encoded using StochSim.

This model is described in the article:

Edelstein SJ, Schaad O, Henry E, Bertrand D, Changeux JP.
Biol Cybern 1996 Nov; 75(5): 361-379

Abstract:

Nicotinic acetylcholine receptors are transmembrane oligomeric proteins that mediate interconversions between open and closed channel states under the control of neurotransmitters. Fast in vitro chemical kinetics and in vivo electrophysiological recordings are consistent with the following multi-step scheme. Upon binding of agonists, receptor molecules in the closed but activatable resting state (the Basal state, B) undergo rapid transitions to states of higher affinities with either open channels (the Active state, A) or closed channels (the initial Inactivatable and fully Desensitized states, I and D). In order to represent the functional properties of such receptors, we have developed a kinetic model that links conformational interconversion rates to agonist binding and extends the general principles of the Monod-Wyman-Changeux model of allosteric transitions. The crucial assumption is that the linkage is controlled by the position of the interconversion transition states on a hypothetical linear reaction coordinate. Application of the model to the peripheral nicotine acetylcholine receptor (nAChR) accounts for the main properties of ligand-gating, including single-channel events, and several new relationships are predicted. Kinetic simulations reveal errors inherent in using the dose-response analysis, but justify its application under defined conditions. The model predicts that (in order to overcome the intrinsic stability of the B state and to produce the appropriate cooperativity) channel activation is driven by an A state with a Kd in the 50 nM range, hence some 140-fold stronger than the apparent affinity of the open state deduced previously. According to the model, recovery from the desensitized states may occur via rapid transit through the A state with minimal channel opening, thus without necessarily undergoing a distinct recovery pathway, as assumed in the standard 'cycle' model. Transitions to the desensitized states by low concentration 'pre-pulses' are predicted to occur without significant channel opening, but equilibrium values of IC50 can be obtained only with long pre-pulse times. Predictions are also made concerning allosteric effectors and their possible role in coincidence detection. In terms of future developments, the analysis presented here provides a physical basis for constructing more biologically realistic models of synaptic modulation that may be applied to artificial neural networks.

To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Le Novère Nicolas lenov@ebi.ac.uk EMBL-EBI 2005-02-02T14:56:11Z 2017-05-19T14:33:51Z

biliganded basal state

monoliganded intermediate

monoliganded active state

unkiganded active state

monoliganded basal state

unliganded basal state

biliganded desensitised state

fully desensitised state

biliganded intermediate

monoliganded desensitised state

unliganted intermediate

biliganted active state

first ligand on basal

kf_0 * B - kr_0 * BL

comp1 kf_0 B kr_0 BL

second ligand on basal

kf_1 * BL - kr_1 * BLL

comp1 kf_1 BL kr_1 BLL

opening of biliganded

kf_2 * BLL - kr_2 * ALL

comp1 kf_2 BLL kr_2 ALL

first ligand on active

kf_3 * A - kr_3 * AL

comp1 kf_3 A kr_3 AL

second ligand on active

kf_4 * AL - kr_4 * ALL

comp1 kf_4 AL kr_4 ALL

opening of unliganded

kf_5 * B - kr_5 * A

comp1 kf_5 B kr_5 A

opening of monoliganded

kf_6 * BL - kr_6 * AL

comp1 kf_6 BL kr_6 AL

first ligand on intermediate

kf_7 * I - kr_7 * IL

comp1 kf_7 I kr_7 IL

second ligand on intermediate

kf_8 * IL - kr_8 * ILL

comp1 kf_8 IL kr_8 ILL

unliganded active <=> unliganded intermediate

kf_9 * A - kr_9 * I

comp1 kf_9 A kr_9 I

monoliganded active <=> monoliganded intermediate

kf_10 * AL - kr_10 * IL

comp1 kf_10 AL kr_10 IL

biliganded active <=> biliganded intermediate

kf_11 * ALL - kr_11 * ILL

comp1 kf_11 ALL kr_11 ILL

first ligand on desensitised

kf_12 * D - kr_12 * DL

comp1 kf_12 D kr_12 DL

second ligand on desensitised

kf_13 * DL - kr_13 * DLL

comp1 kf_13 DL kr_13 DLL

unliganded intermediate <=> unliganded desensitised

kf_14 * I - kr_14 * D

comp1 kf_14 I kr_14 D

monoliganded intermediate <=> monoliganded desensitised

kf_15 * IL - kr_15 * DL

comp1 kf_15 IL kr_15 DL

biliganded intermediate <=> biliganded desensitised

kf_16 * ILL - kr_16 * DLL

comp1 kf_16 ILL kr_16 DLL
time t2 0 0 0 0 0 0 0 0