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. 2014 Sep 30;25(2):149–158. doi: 10.1002/hipo.22359

FIGURE 2.

FIGURE 2

Antagonism of mGlu5 prevents extinction in the AAA paradigm. Animals underwent 20 contiguous trials per day of training in the AAA paradigm. Bar charts represent the percentage of correct arm choices in the first and second set of 10 trials on each test day. Animals participated in 3 days of acquisition training in the AAA paradigm, ending on Day 3 with a 25% reward probability. Control animals were treated with vehicle before re-exposure to the context on Day 4, in the absence of reward. Here, by the second set of 10 trials no significant extinction was evident. Upon being returned to the same context on Day 5 (without reward) an initial recovery of the learned CS–US response was evident in the first set of 10 trials that was followed by significant extinction of the CS–US response. Treatment of animals with the mGlu5 antagonist, MPEP, before re-exposure to the A context in the absence of reward on Day 4 significantly impaired extinction learning. A return to the same context on Day 5 resulted in no significant difference in the level of correct choices (in the first 10 trials) compared to the last 10 trials on Day 4, but under these circumstances significant extinction became evident by the second set of trials. An asterisk indicates a significant effect of at least P < 0.01 between the trials indicated by the bar.