The unique fast spiking (FS) phenotype of cortical parvalbumin-positive (PV) neurons depends on multiple subtypes of voltage-gated potassium channels (Kv). PV neurons selectively express Kcns3, the gene encoding Kv9.3 subunits, suggesting that Kcns3 expression is critical for the FS phenotype. KCNS3 expression is lower in PV neurons in schizophrenia, but the effects of this alteration are unclear, because Kv9.3 subunit function is poorly understood. We therefore assessed the role of Kv9.3 subunits in PV neuron function by combining gene expression analyses, computational modeling, and electrophysiology in acute slices from the cortex of Kcns3-deficient mice Kcns3 mRNA levels were ~50% lower in cortical PV neurons from Kcns3-deficient relative to wildtype mice. While silent per se, Kv9.3 subunits are believed to amplify the Kv2.1 current in Kv2.1-Kv9.3 channel complexes. Hence, to assess the consequences of reducing Kv9.3 levels, we simulated the effects of decreasing the Kv2.1-mediated current in a computational model. The FS cell model with reduced Kv2.1 produced spike trains with irregular inter-spike intervals, or stuttering, and greater Na+ channel inactivation, possibly due to a smaller afterhyperpolarization. As in the computational model, PV basket cells (PVBCs) from Kcns3-deficient mice displayed spike trains with strong stuttering, which depressed PVBC firing, and smaller afterhyperpolarization. Moreover, Kcns3 deficiency impaired the recruitment of PVBCs by stimuli mimicking synaptic input during cortical UP states, which elicited bursts of spikes at gamma frequency. Our data suggest that Kv9.3 subunits are critical for PVBC physiology, and that KCNS3 deficiency in schizophrenia may impair the substrate of gamma oscillations.
bioRxiv Subject Collection: Neuroscience