Dysfunctional parvalbumin interneurons in a genetic mouse model of schizophrenia

The 22q11 deletion syndrome (22q11DS) is an interstitial microdeletion associated to an increased risk of developing schizophrenia. In this disorder, there is a dysfunction in the overall connectivity of the brain. Parvalbumin-expressing (PV+) interneurons have been associated with multiple pre- and post-synaptic impairments that affect various brain regions. Specifically, previous results have suggested that alterations in hippocampal networks may be related to PV+ interneurons dysfunction. In this study, we used the Df1 mouse model that carries the 22q11 deletion to examine the excitability of PV+ cells in the dorsal CA1 region of the hippocampus, due to its importance in memory and cognition. We found that PV+ interneurons were hyperexcitable in this region. To understand the source of the altered excitability, we measured potassium currents, highly involved in the intrinsic firing properties of neurons. We observed that voltage-gated potassium channel subfamily A member 1 (Kv1.1) was impaired in PV+ cells. Specific activation of this channel recovered some of the excitability disturbances observed in Df1 mice. Furthermore, blockade of synaptic inputs also restored PV+ interneurons excitability. Taken together, these results suggest that PV excitability is increased in the CA1 region of the hippocampus and it is partially mediated by Kv1.1 in a mouse model of 22q11DS.