Functional asymmetry and plasticity of electrical synapses interconnecting neurons through a 36-state model of gap junction channel gating
Fig 10
The simulated effect of intracellular free magnesium ion concentration ([Mg2+]i) on junctional conductance and the spread of excitation through electrical synapse formed of Cx36.
A) Simulated kinetics of junctional conductance (gj) of electrical synapse formed of Cx36 under different levels of [Mg2+]i. The parameters of 36SM at [Mg2+]i = 0.8 and 1.2 mM were approximated from optimized values, as presented in S2 Text and S2 Fig. The values of gj were normalised at [Mg2+]i = 1.0 mM. B) The resulting responses between two coupled neurons at steady-state gj reached at [Mg2+]i = 0.8, 1.0 and 1.2 mM. At [Mg2+]i = 0.8 mM, ~2.2-fold increased junctional conductance (~2.2 nS) was sufficient to invoke a postsynaptic response (red curves) to each AP in the presynaptic cell (blue curves). The spread of APs was not disturbed by voltage-gating induced gj decrease (see the upper inset in 10B). At [Mg2+]i = 1.0 mM, the steady-state gj value of ~1 nS was sufficient to transfer each AP initially, but the decreased gj caused a 2-fold lower firing rate in the postsynaptic cell, as compared with [Mg2+]i = 0.8 mM. At [Mg2+]i = 1.2 mM, junctional conductance is decreased ~2.5 fold. Such synaptic strength could only invoke an electrotonic response in the postsynaptic cell.