Opening of KATP Channel Regulates Tonic Currents From Pyramidal Neurons in Rat Brain.

BACKGROUND: ATP-sensitive K+ (KATP) channels couple metabolic state to cellular excitability. Activation of neuronal and astrocytic mitochondrial KATP (mitoKATP) channels regulates a variety of neuronal functions. However, less is known about the impact of mitoKATP on tonic γ-aminobutyric acid (GABA) inhibition. Tonic GABA inhibition is mediated by the binding of ambient GABA on extrasynaptic GABA A-type receptors (GABAARs) and is involved in regulating neuronal excitability.

METHODS: We determined the impact of activation of KATP channels with diazoxide (DIZ) on tonic inhibition and recorded tonic current from rat cortical layer 5 pyramidal cells by patch-clamp recordings.

RESULTS: We found that neonatal tonic current increased with an increase in GABA concentration, which was partially mediated by the GABA A-type receptor (GABAAR) α5, and likely the δ subunits. Activation of KATP channels resulted in decreased tonic current in newborns, but there was increased tonic current during the second postnatal week.

CONCLUSIONS: These findings suggest that activation of KATP channels with DIZ regulates GABAergic transmission in neocortical pyramidal cells during development.