Fig. 4.

Effect of the strychnine-insensitive glycine-recognition site antagonist HA-966 on extinction and on the facilitation of extinction by DCS. A, Timeline of the behavioral procedures for experiment 4. B, Percent fear-potentiated startle measured 24 hr before (pre-extinction test) and 24 hr after (postextinction test) extinction training. Saline or HA-966 (6 mg/kg, i.p.) was administered 10 min before a second injection of saline or DCS, followed 30 min later by a single session of extinction training. HA-966 completely blocked the effects of DCS but did not, on its own, noticeably influence extinction at this dose. *p < 0.05 versus all other groups.