Figure 5

The responses of Ca²⁺ current and concentration to the potential shift via indirect Ca²⁺ inhibition. The intraciliary Ca²⁺ concentration (A) and Ca²⁺ current (B) responses to membrane depolarisation are computed under the assumption of indirect Ca²⁺ channel inhibition for different concentrations of Ca²⁺-sensor protein, Cac₀. The model predicts that in response to fast membrane depolarisation, the ciliary coupled Ca²⁺ and membrane potential system generates an intraciliary Ca²⁺ concentration spike similar to the one observed under the direct Ca²⁺-inhibition assumptions. The non dimensional membrane potential values following voltage shift from the initial ψ₀ = -1.2 are shown in (C) and are the same throughout the figure. The major difference between direct (Figure 3) and indirect mechanisms of inhibition occurs in the steady-state levels of Ca²⁺ concentration that takes place after the transitional process. The comparison of intraciliary Ca²⁺ concentration responses for increasing levels of the Ca²⁺ sensor protein (C, E and G) predicts that intraciliary Ca²⁺ concentrations following the voltage shift are inversely dependent on the Ca²⁺ sensor concentration, Cac₀. Different concentrations of Ca²⁺ sensor protein do not affect the membrane depolarisation-induced Ca²⁺ current (D, F and H).