Elementary, step-like responses in rods lacking rhodopsin phosphorylation. A, Records from knock-out and transgenic rods showing the variable nature of the elementary responses recorded spontaneously in darkness. Dark currents were (in pA) 10.5 (RK–/–), 14.4 (RK–/–Arr–/–), 17.0 (p48RK–/–Arr–/–), and 14.5 (m44RK–/–Arr–/–). B, Frequency distributions of elementary response durations. Distribution of responses from RK–/– and p48 rods were very similar, whereas that of the m44Arr–/– responses resembled that of RK–/–Arr–/– responses. Solid curves are the best fits of scaled exponential functions (e–t/τ or A1e–t/τ1 + A2e–/τ2) with the following parameters: RK–/–, τ = 3.2 s; p48RK–/–Arr–/–, τ = 5.4 s; RK–/–Arr–/–, A1 = 0.16, A2 = 1.0, τ1 = 4.1 s, τ2 = 24.3 s; m44RK–/–Arr–/–, A1 = 0.47, A2 = 1.0, τ1 = 3.7 s, τ2 = 24.2 s.