Developmental increase in [Ca2+]res during paired pulses. (A) Representative traces of ΔF/F0 during paired stimulation [A1, P6; A2, adult (P85); Mg Green]. (B) Ratio of the ∫ΔF/F0 for paired stimuli vs. ∫ΔF/F0 for single stimulus at different developmental ages (P1, n = 4; P3, n = 6; P6, n = 11; P9, n = 6; P15, n = 4; adult, n = 5 animals); *P < 0.05, Student’s t-test against a theoretical mean of 2.