Fig. 5

DHPG-induced increase of intrinsic excitability requires intracellular Ca²⁺. a Left, representative traces demonstrate the effects of DHPG on AP firing frequency and afterpotentials at 120 pA current injections when ryanodine (20 μM) was added to the pipette solutions. Right, FI curve summarizes the effects of DHPG on AP firing frequency in response to square pulse injections (n = 4). b–d Summary plots of the FI curve under the conditions indicated (b, n = 4, 5 mM nicotinamide; c, n = 5, 100 μM 8-NH₂-cADPR; d, n = 5, 3 μM calmidazolium). e Bar graphs summarize the effects of DHPG on afterpotentials following 160 pA square current injections under different conditions indicated (n.s., P > 0.05, *P < 0.05). f and g Summary plots of the FI curve under the conditions indicated (F, n = 8; G, n = 11). h Bar graphs summarize the effects of DHPG on afterpotentials following 160 pA square current injections under different conditions indicated (8 mM BAPTA, n = 8, n.s., P > 0.05; 10 mM EGTA, n = 11, *P < 0.05). Note that DHPG-induced increase of after potential is abolished when 8 mM BAPTA was added to the pipette solutions