KV1 CHANNELS REGULATE THE ELECTROPHYSIOLOGICAL PROPERTIES OF DEEP CEREBELLAR NUCLEI GLYCINERGIC NEURONS

The deep cerebellar nuclei (DCN), the cerebellar output stage, comprise the excitatory principal neurons, the GABAergic nucleo-olivary neurons, and a population of GABAergic/glycinergic neurons that likely modulate DCN output through their local connections and back-projections to the cerebellar cortex. Low-voltage–activated Kv1 channels are abundantly expressed in the cerebellar cortex and nuclei, and Kv1 mutations are associated with episodic ataxias. Although Kv1 channels are known to regulate excitability and synaptic transmission in several cerebellar neuron types, including DCN-GABAergic neurons (Feria-Pliego & Pedroarena, 2020), their role in quiescent DCN-glycinergic neurons remains unclear. Here, we examined the contribution of Kv1 channels to the intrinsic excitability of quiescent DCN-glycinergic neurons using ex-vivo cerebellar slices from >P21 GlyT2-eGFP mice and whole-cell recordings at 35°C in the presence of neurotransmitter antagonists. Pharmacological blockade of specific Kv1 channels (Kv1,1 and Kv1.2 using Dendrotoxin-I or-K) markedly increased neuronal excitability, evidenced by hyperpolarized spike thresholds, increased apparent input-resistance, reduced rheobase, induction of spontaneous firing in previously silent neurons, and enhanced rebound firing. In a subset of neurons, Kv1 blockade elicited spontaneous low-threshold fast rising spikes, suggesting Kv1 channels control these neurons axonal excitability. Post-hoc analysis of biocytin filled recorded neurons confirmed eGFP expression and demonstrated GlyT2 (glycine-transporter 2) immuno-reactivity in putative axonal boutons, confirming their glycinergic identity. Together, these findings demonstrate that Kv1 channels critically regulate the excitability of quiescent DCN-glycinergic neurons, and thereby these neurons function within the cerebellar circuit. Furthermore, the results suggest that DCN-glycinergic neurons dysregulation contributes to altered cerebellar output in Kv1 channelopathies.