Figure 4.

Ca²⁺ spiking leads to E_gly shifts. A, Glycine responses (2 mm, marked by arrowheads) shifted negative during a prolonged period of Ca²⁺ spiking. Spikes were evoked for 42 s by +70 pA from −30 pA bias. A negative shift and recovery in E_gly was evident as the polarity of glycine responses changed from depolarizing to hyperpolarizing after Ca²⁺ spiking and back to depolarizing. The hyperpolarization to −80 mV at 2 s into the stimulus was an afterhyperpolarization of the first Ca²⁺ spike, and the fluctuation of V_m during 10 s after Ca²⁺ spiking is thought to be a manifestation of the intrinsic bistability of CWCs. B, Plot of the peak negative (neg) shift in E_gly versus the number of high-threshold Ca²⁺ spikes evoked during an 8 s challenge protocol. Dots represent 148 E_gly series from 83 CWCs. 104 series are from 55 cells recorded with AM dye solution and 44 series from 28 cells without dye. C, The shifts in E_gly at 2 s after an 8 s Ca²⁺ spiking (i), complex spiking (ii), or simple spiking (iii) are plotted against the peak negative shift of the E_gly series. Dots in each plot represent single E_gly series from different cells, with n = 44, 29, and 8 for i, ii, and iii, respectively. All data were obtained in TTX except for that shown in Cii, iii.