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Potassium-coupled chloride cotransport controls intracellular chloride in rat neocortical pyramidal neurons.

ABSTRACT: Chloride (Cl(-)) homeostasis is critical for many cell functions including cell signaling and volume regulation. The action of GABA at GABA(A) receptors is primarily determined by the concentration of intracellular Cl(-). Developmental regulation of intracellular Cl(-) results in a depolarizing response to GABA in immature neocortical neurons and a hyperpolarizing or shunting response in mature neocortical neurons. One protein that participates in Cl(-) homeostasis is the neuron-specific K(+)-Cl(-) cotransporter (KCC2). Thermodynamic considerations predict that in the physiological ranges of intracellular Cl(-) and extracellular K(+) concentrations, KCC2 can act to either extrude or accumulate Cl(-). To test this hypothesis, we examined KCC2 function in pyramidal cells from rat neocortical slices in mature (18-28 d postnatal) and immature (3-6 d postnatal) rats. Intracellular Cl(-) concentration was estimated from the reversal potential of whole-cell currents evoked by local application of exogenous GABA. Both increasing and decreasing the extracellular K(+) concentration resulted in a concomitant change in intracellular Cl(-) concentration in neurons from mature rats. KCC2 inhibition by furosemide caused a change in the intracellular Cl(-) concentration that depended on the concentration of pipette Cl(-); in recordings with low pipette Cl(-), furosemide lowered intracellular Cl(-), whereas in recordings with elevated pipette Cl(-), furosemide raised intracellular Cl(-). In neurons from neonatal rats, manipulation of extracellular K(+) had no effect on intracellular Cl(-) concentration, consistent with the minimal KCC2 mRNA levels observed in neocortical neurons from immature animals. These data demonstrate a physiologically relevant and developmentally regulated role for KCC2 in Cl(-) homeostasis via both Cl(-) extrusion and accumulation.

SUBMITTER: DeFazio RA

PROVIDER: S-EPMC6772739 | biostudies-literature | 2000 Nov

REPOSITORIES: biostudies-literature

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Potassium-coupled chloride cotransport controls intracellular chloride in rat neocortical pyramidal neurons.

DeFazio R A RA Keros S S Quick M W MW Hablitz J J JJ

The Journal of neuroscience : the official journal of the Society for Neuroscience 20001101 21

Chloride (Cl(-)) homeostasis is critical for many cell functions including cell signaling and volume regulation. The action of GABA at GABA(A) receptors is primarily determined by the concentration of intracellular Cl(-). Developmental regulation of intracellular Cl(-) results in a depolarizing response to GABA in immature neocortical neurons and a hyperpolarizing or shunting response in mature neocortical neurons. One protein that participates in Cl(-) homeostasis is the neuron-specific K(+)-Cl ...[more]

PMID: 11050128

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Project description:BACKGROUND:Interferon-? (IFN-?, a type II IFN) is present in the central nervous system (CNS) under various conditions. Evidence is emerging that, in addition to its immunological role, IFN-? modulates neuronal morphology, function, and development in several brain regions. Previously, we have shown that raising levels of IFN-? (a type I IFN) lead to increased neuronal excitability of neocortical layer 5 pyramidal neurons. Because of shared non-canonical signaling pathways of both cytokines, we hypothesized a similar neocortical role of acutely applied IFN-?. METHODS:We used semi-quantitative RT-PCR, immunoblotting, and immunohistochemistry to analyze neuronal expression of IFN-? receptors and performed whole-cell patch-clamp recordings in layer 5 pyramidal neurons to investigate sub- and suprathreshold excitability, properties of hyperpolarization-activated cyclic nucleotide-gated current (Ih), and inhibitory neurotransmission under the influence of acutely applied IFN-?. RESULTS:We show that IFN-? receptors are present in the membrane of rat's neocortical layer 5 pyramidal neurons. As expected from this and the putative overlap in IFN type I and II alternative signaling pathways, IFN-? diminished Ih, mirroring the effect of type I IFNs, suggesting a likewise activation of protein kinase C (PKC). In contrast, IFN-? did neither alter subthreshold nor suprathreshold neuronal excitability, pointing to augmented inhibitory transmission by IFN-?. Indeed, IFN-? increased electrically evoked inhibitory postsynaptic currents (IPSCs) on neocortical layer 5 pyramidal neurons. Furthermore, amplitudes of spontaneous IPSCs and miniature IPSCs were elevated by IFN-?, whereas their frequency remained unchanged. CONCLUSIONS:The expression of IFN-? receptors on layer 5 neocortical pyramidal neurons together with the acute augmentation of inhibition in the neocortex by direct application of IFN-? highlights an additional interaction between the CNS and immune system. Our results strengthen our understanding of the role of IFN-? in neocortical neurotransmission and emphasize its impact beyond its immunological properties, particularly in the pathogenesis of neuropsychiatric disorders.

Dataset Information

Potassium-coupled chloride cotransport controls intracellular chloride in rat neocortical pyramidal neurons.

Publications

Potassium-coupled chloride cotransport controls intracellular chloride in rat neocortical pyramidal neurons.

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