Influence of chronic fluoxetine treatment on apetitive learning in matrix metalloproteinase-9 knock-out mice

Matrix metalloproteinase-9 (MMP-9) is an extracellular endopeptidase which cleaves extracellular matrix proteins and plays a significant role in synaptic plasticity, learning and memory. Impairment of MMP-9 knock-out mice in appetitively motivated learning has been previously shown. In the present project we investigated whether chronic treatment with fluoxetine, antidepressant drug, which stimulates synaptic plasticity, would affect appetitive learning of MMP-9 knock-out mice. To this end, MMP-9 knock-out and wild type mice were treated with fluoxetine or vehicle for 35 days, and trained in sucrose-water discrimination task in the IntelliCage system. The IntelliCage system allows for long-term monitoring of the behavior of group-housed animals. For five days the mice had to discriminate between bottles (placed on two sides of the same corner of the cage) that contained either sweetened or plain water. The results suggest that chronic fluoxetine treatment improves appetitive learning of MMP-9 knock-out mice.