Relief learning is an appetitive association of a formally neutral cue with relief induced
by the offset of an aversive stimulus. Since the nucleus accumbens mediates relief learning and
accumbal metabotropic glutamate receptors 7 (mGluR7) modulate appetitive-like processes, we
hypothesized that accumbal mGluR7 may be involved in the modulation of relief learning.
Therefore, we injected the allosteric mGluR7 agonist AMN082 into the nucleus accumbens and
tested the effects of these injections on acquisition and expression of relief memory, as well as on
the reactivity to electric stimuli. AMN082 injections blocked acquisition but not expression of
relief memory. In addition, accumbal AMN082 injections strongly reduced the locomotor reactivity to electric stimuli
indicating antinociceptive effects. These antinociceptive effects might be causal for the blockade of relief learning after
AMN082 injections. Taken together, the present study indicates that functional activation of accumbal mGluR7 has
antinociceptive effects that interfere with relief learning.
Keywords: AMN082, mGluR7, nucleus accumbens, pain, rat, relief.
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