Behavioural phenotyping reveals anxiety-like features of SV2A deficient mice

Synaptic vesicle protein 2A (SV2A) is involved in neurotransmitter release and has been identified as the binding site for levetiracetam (Keppra®), a novel antiepileptic drug. Homozygous SV2A (−/−) mice are not viable beyond a few weeks. In contrast, heterozygous SV2A (+/−) mice have a normal lifespan. We performed a behavioural phenotyping on SV2A (+/−) mice in a battery of tests: gross behavioural observation, spontaneous locomotor activity, sensori-motor coordination, acute pain sensitivity, exploration in an elevated plus-maze and an assessment of learning abilities in an inhibitory avoidance procedure. SV2A (+/−) mice were compared to age-matched, 2-month-old wild type controls. Overall, gross behaviour, spontaneous locomotor activity, sensori-motor coordination and acute pain sensitivity were comparable between wild type and SV2A (+/−) mice. When tested in a plus-maze, SV2A (+/−) mice displayed significant increased avoidance of open elevated arms whereas locomotor activity was not altered. Finally, both SV2A (+/−) and wild type mice showed comparable memory performance at the end of a multi-trial passive avoidance procedure. Interestingly, SV2A (+/−) mice exhibited increased avoidance of the lit area during the first sessions without foot shock. These results suggest an anxiety-like phenotype for SV2A (+/−) mice indicated by increased open-arm avoidance in the elevated plus-maze test as well as a shorter latency to escape from a lit area in the inhibitory avoidance procedure.