Figure 6. Effects of TSP4 on intracellular calcium transient in DRG neurons.

A, Bath application of 50 mM K⁺ for 1s depolarized sensory neurons to −12 ± 2mV (left panel, n = 3), and 50 mM K⁺ for 0.3s depolarized neurons to −31.3 ± 2.9mV (right panel, n = 3). B, 1s depolarization induced intracellular Ca²⁺ transient that was resistant to the T-type Ca²⁺ channel blocker TTA-P2 (left panel, typical of n = 8), while the intracellular calcium transient induced by 50mM K⁺ for 0.3s could be blocked by TTA-P2 (right panel, typical of n = 10). To avoid membrane depolarization from AP generation, TTX (1 µM) was added during subsequent recordings. C, TSP4 treatment reduced intracellular Ca²⁺ transients induced by 50 mM K⁺ for 1s. D, In contrast, TSP4 treatment increased intracellular Ca²⁺ transients induced by 50 mM K⁺ for 0.3s. ** P < 0.01 by Student’s t test.