Seven-day nicotine exposure prior to cocaine enhances LTP in the Dentate Gyrus (DG). (A) A single tetanus (1 × 100 Hz) induced a weak LTP in DG. Top panel shows the schematic illustration of LTP recording in the DG. (B) Oral administration of nicotine for 7 d did not alter LTP. (C) Single injection of cocaine did not alter LTP. (D) Seven-day nicotine treatment followed by cocaine injection significantly enhanced LTP. (Closed circles) nicotine + cocaine, (open squares) cocaine. (E) There is no significant difference in the input–output curves between mice treated with 7-d nicotine/cocaine and control mice. Top panels of each graph show the representative EPSPs before and 50 min after tetanus. Calibration: 10 msec, 1 mV.
