The finding that mGlu5 antagonism differentiates between extinction learning of the conditioned response in the "A" context, and extinction in learning in the "B" context is intriguing.
On Day 5, the animals were returned to the "A" context that they had experienced on Days 1 3, except here no reward was given.
We observed that although extinction learning in the A context (AAA, in the absence of food reward) was effective and significant, it was greatly improved by a context change (ABA).
In contrast, mGlu5 antagonism does not alter improved extinction learning in the "B" context of the ABA paradigm but significantly impairs subsequent extinction following renewal of the conditioned response in the "A" context.
Strikingly, although significant renewal occurred in the A context on Day 5 (Fig. 3) (P < 0.001, first 10 trials, Day 5 versus last 10 trials, Day 4), it was not followed by significant extinction (first 10 trials, Day 5 versus last 10 trials, Day 5, P = 0.285).
before exposure to the "A" context on Day 4, no significant decline in correct choice performance was evident within the MPEP group (comparison of last 10 trials on Day 3 with first 10 trials of Day 4: P = 0.461; first 10 trials of Day 4 versus last 10 trials of Day 4, P = 0.07).
