Fig. 1. Developmental increase in the magnitude of calcium current recorded via perforated patch-clamp techniques from embryonic chick ciliary ganglion neurons. A, Representative examples of calcium current recorded from three embryonic stages (stage 40, top traces; stage 37, middle traces; stage 34, bottom traces) in response to voltage steps from −80 to −40 mV through 10 mV. B, Current–voltage relationship of currents recorded at stage 34 (filled circles), stage 37 (open triangles), and stage 40 (filled triangles). Values represent the mean ± SEM of 10 representative cells from each embryonic age.C, Current density–voltage relationship for the same data shown in B. D, Representative time course of the development of electrical access during the initiation of perforated patch recordings. Overlapping records were taken 5, 30, 60, 90, 120, 150, 180, and 360 sec after seal formation. In this example, at 360 sec the capacitance measured 9.7 pF, and the time constant for decay of the capacitive transient measured 0.08 msec (access resistance, 9.1 MΩ).