Figure 8. Sensitization requires GABAergic transmission.

(A) Top, the stimulus changed back and forth for 80 trials between a global high contrast (35 %) for 4 s and a global low contrast (3 %) for 16 s. Middle, example average responses for sensitizing cells during the 30 min prior to drug addition (left), and from 30 min to 1h after drug addition (right), for a cell in 100 μM picrotoxin. Bottom, same for a different sensitizing cell in 200 μM bicuculline methiodide. (B) Average adaptive indices for sensitizing cells in (top) picrotoxin (n = 4) or (bottom) bicuculline (n = 5). Error bars are obscured by the data. (C) The response of a cell with a center-surround adaptive field to the stimulus from Figure 1A,B before and during the addition of 75 μM picrotoxin. High contrast stimulus was positioned in the sensitizing region of the cell. (D) Average adaptive indices as a function of distance for fast Off adapting cells (top) (n = 68) and sensitizing cells (bottom) in control solution and 75 μM (n = 12, closed circles) or 200 μM (n = 6, open circles) picrotoxin. Responses are shown before drug (colored circles) and after drug (black circles). Error bars are s.e.m.