Figure 4. Ca²⁺ spiking leads to E_gly shifts.

(A) Glycine responses (2mM, marked by arrowheads) shifted negative during long prolonged period of Ca²⁺ spiking. Spikes were evoked for 42 sec 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 depolarizating to hyperpolarizating after Ca²⁺ spiking and back to depolarizating. The hyperpolarization to −80 mV at 2 sec into the stimulus was an afterhyperpolarization of the first Ca²⁺ spike, and the fluctuation of V_m during 10 sec after Ca²⁺ spiking is thought to be a manifestation of the intrinsic bistability of CWCs. (B) Plot of the peak negative shift in E_gly versus the number of high-threshold Ca²⁺ spikes evoked during an 8-sec 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 sec after an 8-sec 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 (Cii-iii).