Requirement of Akt to Mediate Long-Term Synaptic Depression in Drosophila

Normal synaptic transmission and short-term plasticity (E–G) in the akt mutants akt⁴²²⁶ and akt⁴²²⁶/akt¹. A, Representative traces of spontaneous mEJCs in wild type (WT) and the akt mutants. Calibration: 1 nA, 1 s. B, Summary of amplitude and frequency of mEJCs. n = 8 and 6 for WT and akt groups, respectively. C, Representative traces of EJCs at different Ca²⁺ concentrations (0.1, 0.2, and 0.4 mm) in wild type and the akt mutants. Calibration: for 0.1 and 0.2 mm Ca²⁺, 10 nA, 10 ms; for 0.4 mm Ca²⁺, 20 nA, 10 ms. D, Ca²⁺ dependency of EJCs: logarithmic plot of the power relationship in the range of 0.1–0.4 mm Ca²⁺. n = 6, 6, and 4 for the control (diamond), akt⁴²²⁶ (square), and akt⁴²²⁶/akt¹ (triangle) groups, respectively. E, Normal STF during a short train of repetitive stimulation (25 Hz) in the akt mutants. Top, Representative traces. Bottom, Summary of normalized EJC amplitude. n = 5 for each group. F, Normal dependence of STF on stimulation frequency in the akt mutants. Trains of 20 stimuli were delivered at the frequency of 0.5–20 Hz. The amplitudes of the last 10 responses (EJCs) in each train were averaged and normalized to the average EJC amplitude at 0.5 Hz. Top, EJC traces representative of the average of last 10 EJCs for 0.5 and 10 Hz. Calibration: 2 nA, 10 ms. Bottom, Summary. n = 5 for each group. G, Normal posttetanic potentiation in the akt mutants. Continuous recordings were made at 0.2 Hz stimulation before and after the 10 Hz tetanus. Top, Representative traces. Calibration: 5 nA, 1 min. Bottom, Summary of normalized EJC amplitudes. n = 11, 10, and 6 for control, akt⁴²²⁶, and akt⁴²²⁶/akt¹ groups, respectively. [Ca²⁺], 0.15 mm for E–G.