Siu 102b

Cultured neurons on coverslips were placed in a stimulation chamber (RC-49MFSH, Warner Instruments) and stimulated at an intensity of 10 V/cm using a stimulus isolation unit (SIU-102B, Warner Instruments). Stimulation duration and frequency was controlled by an isolated pulse stimulator (2100, A-M Systems). Neurons were imaged in standard extracellular saline containing (in mM): NaCl 150, KCl 3, Glucose 20, HEPES 10, CaCl₂ 2, MgCl₂ 3, pH adjusted to 7.35 with NaOH, 310 mOsm; unless indicated otherwise.

The fear conditioning chamber (context-A) is equipped with steel rods on the floor for delivering electric shocks controlled by a stimulus isolation unit (SIU-102B, Warner Instruments, Hamden CT, USA). Freezing behavior (no noticeable movement for ≥1 s) was analyzed by “ANY-Maze” software. After rats were placed in the conditioning chamber for 90 s, three 30 s tones, each of which co-terminated with a 2 s foot shock, were presented every 2 min. The percentage of freezing for every 2 min conditioning session was plotted as conditioning response. Tones were 2.8 kHz sine waves (90 dB).