Fig. 7.

Refilling of the ryanodine-sensitive store by Ca²⁺ influx produced by 20 Hz nerve firing. A,The superimposed traces are the Δ[Ca²⁺]_i in response to the first stimulation (200 stimuli) recorded from a unit in normal Ringer solution (NR) and in 10 μmryanodine (RY). Note that it was not inhibited by RY.B, The superimposed traces are the responses to the subsequent stimulation (400 stimuli), which was 2 min after the beginning of the 200 stimuli train in NR and in 10 μm RY. This response was reduced by RY. C, D, Superimposed traces are the first 20 sec of the Δ[Ca²⁺]_i evoked by 200 and 400 stimuli recorded in NR (C) and in RY (D). The thin line at the bottom of each panel indicates the 0 [Ca²⁺]_i level. Thevertical dotted line at the left in each panel indicates the time when the stimulation began, and the vertical dotted line at the right indicates 10 sec (A, C, D) and 20 sec (B) later.