SELECTIVE ENHANCEMENT OF EMOTIONAL, BUT NOT MOTOR, LEARNING IN MONOAMINE-OXIDASE A-DEFICIENT MICE

Mice deficient in monoamine oxidase A (MAOA), an enzyme that metaboliz es monoamines such as norepinephrine and serotonin, have elevated nore pinephrine and serotonin levels in the frontal cortex, hippocampus, an d cerebellum, compared with normal wild-type mice, Since monoamines in these areas are critically involved in a variety of behaviors, we exa mined learning and memory (using emotional and motor tasks) in MAOA mu tant mice, The MAOA-deficient mice exhibited significantly enhanced cl assical fear conditioning (freezing to both tone and contextual stimul i) and step-down inhibitory avoidance learning. In contrast, eyeblink conditioning was normal in these mutant mice, The female MAOA-deficien t mice also displayed normal species-typical maternal behaviors (nesti ng, nursing, and pup retrieval), These results suggest that chronic el evations of monoamines, due to a deletion of the gene encoding MAOA, l ead to selective alterations in emotional behavior.