Clorgyline-mediated reversal of neurological deficits in a Complexin 2 knockout mouse.
Complexin 2 is a protein modulator of neurotransmitter release that is downregulated in humans suffering from depression, animal models of depression and neurological disorders such as Huntington's disease in which depression is a major symptom. Although complexin 2 knockout (Cplx2-/-) mice are overtly normal, they show significant abnormalities in cognitive function and synaptic plasticity. Here we show that Cplx2-/- mice also have disturbances in emotional behaviours that include abnormal social interactions and depressive-like behaviour. Since neurotransmitter deficiencies are thought to underlie depression, we examined neurotransmitter levels in Cplx2-/- mice and found a significant decrease in levels of noradrenaline and the serotonin metabolite 5-hydroxyindoleacetic acid in the hippocampus. Chronic treatment with clorgyline, an irreversible inhibitor of monoamine oxidase A, restored hippocampal noradrenaline to normal levels (from 60 to 97% of vehicle-treated Cplx2+/+ mice, P