Figure 8. Quantification of spontaneous synaptic efficacy fluctuations due to the fast exchange of receptors between synapses and the receptor pool.

(A) Example simulation of a piece of dendrite with 7 synapses during 10 min of simulated time. The number of receptor slots in each synapse is given in the legend. The relative pool size was set to $\varphi =2.67$ and the filling fraction was set to $F=0.5$ by choosing the binding rate to receptor slots $\alpha$ via Equation 13. (B) Same as A. but for a higher filling fraction of $F=0.9$. (C) Size of synaptic efficacy fluctuations as measured by the coefficient of variation (CV) as a function of the steady state number of receptors in each synapse, which is given by the product of the filling fraction $F$ and the number of slots $s_i$ in synapse $i$. The relative pool size was set to $\varphi =2.67$. Data points represent averages over 10 simulations of 30 min simulated time each. Lines represent linear fits through the data points in double log space. (D) CV as a function of steady state number of receptors for different relative pool sizes $\varphi$ achieved by holding the binding rate to receptor slots $\alpha$ fixed and varying the externalization rate $\gamma$.