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. Author manuscript; available in PMC: 2013 Oct 18.
Published in final edited form as: Neuron. 2012 Oct 17;76(2):370–382. doi: 10.1016/j.neuron.2012.07.029

Figure 2. Depletion of Available PDE Molecules and Local Channel Saturation Do Not Explain Amplitude Stability for Long R* Lifetimes.

Figure 2

(A) Simulated SPR of Grk1+/− rods (solid) superimposed upon the calculated number of G*-E* (dashed) produced as a function of time, assuming that R* activates G*-E* at a maximal rate of 300 s−1, with an effective lifetime τReff = 76 ms, and a G*-E* lifetime of 200 ms.

(B) Spatial profile of cGMP concentration at three time points corresponding to the colored circles in (A). The fall in cGMP at the local site of photoisomerization is maximal at the SPR peak but does not exceed 18% of the dark cGMP concentration. Thus, local channel saturation contributes only slightly to the large degree of amplitude stability observed when R* lifetime is increased 2-fold beyond its WT level.