Figure 3. Influence of ryanodine receptor and L-type Ca²⁺ channel activation on [Ca²⁺]_i in confluent cultures of ARPE-19 cells. A: Application of 50 mM caffeine leads to an instantaneous [Ca²⁺]_i increase followed by a sustained decrease. B: 50 mM caffeine induced a significant increase in [Ca²⁺]_i (p<0.05, n=6). C: Activation of L-type Ca²⁺ channels by 5 μM BayK8644 did not influence [Ca²⁺]_i levels in ARPE-19 cells. D: Mean [Ca²⁺]_i did not differ before and during application of 5 μM BayK8644 (n=6). E: Inhibition of BK channels by 100 nM iberiotoxin did not influence [Ca²⁺]_i levels in ARPE-19 cells. F: Mean [Ca²⁺]_i did not differ before and during application of 100 nM iberiotoxin (n=5).