Upregulation of A-type potassium channels suppresses neuronal excitability in hypoxic neonatal mice.

Neuronal excitability is a critical feature of central nervous system development, playing a fundamental role in the functional maturation of brain regions, including the hippocampus, cerebellum, auditory and visual systems. The present study aimed to determine the mechanism by which hypoxia causes brain dysfunction through perturbation of neuronal excitability in a hypoxic neonatal mouse model. Functional brain development was assessed in humans using the Gesell Development Diagnosis Scale. In mice, gene transcription was evaluated via mRNA sequencing and quantitative PCR; furthermore, patch clamp recordings assessed potassium currents. Clinical observations revealed disrupted functional brain development in 6- and 18-month-old hypoxic neonates, and those born with normal hearing screening unexpectedly exhibited impaired central auditory function at 3 months. In model mice, CA1 pyramidal neurons exhibited reduced spontaneous activity, largely induced by excitatory synaptic input suppression, despite the elevated membrane excitability of hypoxic neurons compared to that of control neurons. In hypoxic neurons, Kcnd3 gene transcription was upregulated, confirming upregulated hippocampal K 4.3 expression. A-type potassium currents were enhanced, and K 4.3 participated in blocking excitatory presynaptic inputs. Elevated K 4.3 activity in pyramidal neurons under hypoxic conditions inhibited excitatory presynaptic inputs and further decreased neuronal excitability, disrupting functional brain development in hypoxic neonates.