kCC2

Long before the molecular identity of the Na(+)-dependent K(+)-Cl(-) cotransporters was uncovered in the mid-nineties, a Na(+)-independent K(+)-Cl(-) cotransport system was also known to exist. It was initially observed in sheep and goat red blood cells where it was shown to be ouabain-insensitive and to increase in the presence of N-ethylmaleimide (NEM). After it was established between the early and mid-nineties, the expressed sequence tag (EST) databank was found to include a sequence that was highly homologous to those of the Na(+)-dependent K(+)-Cl(-) cotransporters...

Deficits in GABAergic inhibition result in the abnormal neuronal activation and synchronization that underlies seizures. However, the molecular mechanisms responsible for transforming a normal brain into an epileptic one remain largely unknown. Hyperpolarizing inhibition mediated by type A GABA (GABAA) receptors is dependent on chloride extrusion by the neuron-specific type 2K(+)-Cl(-) cotransporter (KCC2). Loss-of-function mutations in KCC2 are a known cause of infantile epilepsy in humans and KCC2 dysfunction is present in patients with both idiopathic and acquired epilepsy...

In addition to cortical areas, the thalamus also displays plasticity during a critical period in early life. Since most sensory information is transmitted to the cortex via the thalamus, it will be of significant interest to understand the precise time window and underlying mechanisms of this critical period in the thalamus. By using in vitro whole-cell patch recording in acute brain slices, we found that VPm relay synapses were only sensitive to whisker deprivation from postnatal day 11 (P11) to P14. Whisker deprivation initiated within the P11 to P14 window significantly reduced the amplitude of AMPAR-EPSCs, but not NMDAR-EPSCs when recorded 24 h after whisker removal...

In mature neurons, low intracellular chloride level required for inhibition is maintained by the potassium-chloride co-transporter KCC2. Impairment of Cl- extrusion following KCC2 dysfunction has been involved in many CNS disorders such as seizures, neuropathic pain or spasticity after a spinal cord injury (SCI). This makes KCC2 an appealing drug target for restoring Cl-homeostasis and inhibition in pathological conditions. In the present study, we screen the Prestwick Chemical Library® and identify conventional antipsychotics phenothiazine derivatives as enhancers of KCC2 activity...

The pain sensory system normally functions under a fine balance between excitation and inhibition. When this balance is perturbed for some reason, it leads to neuropathic pain. There is accumulating evidence that attributes this pain generation to specific dysfunctions of the inhibitory system in the spinal cord. One possible mechanism leading to the induction of these dysfunctions is the down-regulation of K(+)-Cl(-)-cotransporter-2 (KCC2) expression. In fact, various neuropathic pain models indicate a decrease of KCC2 expression in the spinal cord...

Decreased inhibition plays an extremely important role in pathogenesis of autism spectrum disorder (ASD). Therefore, we aimed to determine whether expression levels of the γ-aminobutyric acid type A receptor β3 subunit (GABAARβ3), K(+)-Cl(-) cotransporter 2 (KCC2), and Na(+)-K(+)-Cl(-) cotransporter 1 (NKCC1) related to inhibition transmission are changed in a sodium valproate-induced rat model of ASD. Decreased expression levels of membrane GABAARβ3 (m-GABAARβ3) and KCC2 as well as increased endocytosis of GABAARs were found in the model group...

Morphine-induced hyperalgesia (MIH) is a severe adverse effect accompanying repeated morphine treatment, causing a paradoxical decrease in nociceptive threshold. Previous reports associated MIH with a decreased expression of the Cl(-) extruder KCC2 in the superficial dorsal horn (SDH) of the spinal cord, weakening spinal GABAA/glycine-mediated postsynaptic inhibition. Here, we tested whether the administration of small molecules enhancing KCC2, CLP257 and its pro-drug CLP290, may counteract MIH. MIH was typically expressed within 6-8 days of morphine treatment...

Intracellular chloride concentration ([Cl(-)]i) in pancreatic β-cells is kept above electrochemical equilibrium due to the predominant functional presence of Cl(-) loaders such as the Na(+)K(+)2Cl(-) co-transporter 1 (Slc12a2) over Cl(-)extruders of unidentified nature. Using molecular cloning, RT-PCR, Western blotting, immunolocalization and in vitro functional assays, we establish that the "neuron-specific" K(+)Cl(-) co-transporter 2 (KCC2, Slc12a5) is expressed in several endocrine cells of the pancreatic islet, including glucagon secreting α-cells, but particularly in insulin-secreting β-cells, where we provide evidence for its role in the insulin secretory response...

Epilepsy of infancy with migrating focal seizures (EIMFS) is an infantile epileptic encephalopathy characterized by refractory seizures, severe psychomotor delay, and multiple moving epileptic discharges. The genetic etiology of EIMFS is relatively homogeneous with the majority of causative mutations found in KCNT1. Currently, gene panel or whole-exome sequencing is used for testing. To verify the pathogenicity of a variant, co-segregation of the variant and the disorder in a pedigree is important; hence, de novo mutations that are judged to be deleterious may be considered pathogenic because the patients are isolated...

PURPOSE OF REVIEW: Dietary salt intake increases both plasma sodium and osmolality and therefore increases vasopressin (VP) release from the neurohypophysis. Although this effect could increase blood pressure by inducing fluid reabsorption and vasoconstriction, acute activation of arterial baroreceptors inhibits VP neurons via GABAA receptors to oppose high blood pressure. Here we review recent findings demonstrating that this protective mechanism fails during chronic high salt intake in rats...

GABAB receptors are G-protein-coupled receptors that mediate inhibitory synaptic actions through a series of downstream target proteins. It is increasingly appreciated that the GABAB receptor forms part of larger signaling complexes, which enable the receptor to mediate multiple different effects within neurons. Here we report that GABAB receptors can physically associate with the potassium-chloride cotransporter protein, KCC2, which sets the driving force for the chloride-permeable ionotropic GABAA receptor in mature neurons...

BACKGROUND: The majority of studies evaluating neurocognition in humans who had procedures under anesthesia early in life found long-term deficits even though the typical anesthesia duration normalized to the human life span is much shorter than that shown to induce developmental abnormalities in rodents. Therefore, we studied whether subsequent environmental stressors contribute to deficiencies programmed by a brief neonatal etomidate exposure. METHODS: Postnatal days (P) 4, 5, or 6, Sprague-Dawley rats, pretreated with vehicle or the Na(+)-K(+)-2Cl(-) (NKCC1) inhibitor, bumetanide, received two injections of etomidate resulting in anesthesia for 2h...

Changes in chloride reversal potential in rat spinal cord neurons have previously been associated with persistent pain in nerve injury and inflammation models. These changes correlate with a decrease in the expression of the potassium chloride transporter, KCC2, and with increases in neuronal excitability. Here, we test the hypothesis that similar changes occur in mice with neuropathic pain induced by chronic constriction injury of the trigeminal infraorbital nerve (CCI-ION). This model allows us to distinguish an acute pain phase (3-5 days after injury) from a persistent pain phase (12-14 days after CCI-ION)...

Background Accumulating evidence has shown that the signal from spinal brain-derived neurotrophic factor/tyrosine receptor kinase B-K(+)-Cl(-) cotransporter-2 plays a critical role in the process of pain hypersensitivity. The activation of alpha-7 nicotinic acetylcholine receptors could have an analgesic effect on remifentanil-induced postoperative hyperalgesia. Nevertheless, whether intrathecal administration of PNU-120596, an alpha-7 nicotinic acetylcholine receptors selective type II positive allosteric modulator, before surgery could affect the duration of remifentanil-induced postoperative hyperalgesia remains unknown, and the effects of alpha-7 nicotinic acetylcholine receptors activation on the brain-derived neurotrophic factor/tyrosine receptor kinase B-K(+)-Cl(-) cotransporter-2 signal in the spinal dorsal horn of rats with remifentanil-induced postoperative hyperalgesia is still enigmatic...

Approximately 7% to 10% of patients develop a chronic pain syndrome after stroke. This chronic pain condition is called central poststroke pain (CPSP). Recent studies have observed an abnormal increase in the secretion of brain-derived neurotrophic factor (BDNF) in spinal cord tissue after spinal cord injury. An animal model of CPSP was established by an intrathalamus injection of collagenase. Mechanical and thermal allodynia was induced after lesions of the thalamic ventral basal complex in rats. Four weeks after the injection, the number of neurons decreased, the number of astrocytes, microglia, and P2X4 receptors increased, and BDNF mRNA expression increased in the brain lesion area...

Maintenance of a low intraneuronal Cl(-) concentration, [Cl(-)]i, is critical for inhibition in the CNS. Here, the contribution of passive, conductive Cl(-) flux to recovery of [Cl(-)]i after a high load was analyzed in mature central neurons from rat. A novel method for quantifying the resting Cl(-) conductance, important for [Cl(-)]i recovery, was developed and the possible contribution of GABAA and glycine receptors and of ClC-2 channels to this conductance was analyzed. The hypothesis that spontaneous, action potential-independent release of GABA is important for [Cl(-)]i recovery was tested...

The neurodevelopmental factor dysbindin is required for synapse function and GABA interneuron development. Dysbindin protein levels are reduced in the hippocampus of schizophrenia patients. Mouse dysbindin genetic defects and other mouse models of neurodevelopmental disorders share defective GABAergic neurotransmission and, in several instances, a loss of parvalbumin-positive interneuron phenotypes. This suggests that mechanisms downstream of dysbindin deficiency, such as those affecting GABA interneurons, could inform pathways contributing to or ameliorating diverse neurodevelopmental disorders...

The amyloid precursor protein (APP) modulates synaptic activity, resulting from the fine tuning of excitatory and inhibitory neurotransmission. GABAergic inhibitory neurotransmission is affected by modifications in intracellular chloride concentrations regulated by Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1) and neuronal K(+)-Cl(-) cotransporter 2 (KCC2), allowing entrance and efflux of chloride, respectively. Modifications in NKCC1 and KCC2 expression during maturation of cortical cells induce a shift in GABAergic signaling...

Positive transfer of secondary focus (PTS) refers to new epileptogenesis outside the primary focus and is minimally controlled by existing treatments. Low-frequency stimulation (LFS) has benefits on the onset of epilepsy and epileptogenesis. However, it's unclear whether LFS can retard the PTS in epilepsy. Here we found that PTS at both contralateral amygdala and ipsilateral hippocampus were promoted after the primary focus was fully kindled in rat kindling model. The promotion of PTS at the mirror focus started when the primary kindling acquisition reached focal seizures...

BACKGROUND: General anesthetics potentiating γ-aminobutyric acid (GABA)-mediated signaling are known to induce a persistent decrement in excitatory synapse number in the cerebral cortex when applied during early postnatal development, while an opposite action is produced at later stages. Here, the authors test the hypothesis that the effect of general anesthetics on synaptogenesis depends upon the efficacy of GABA receptor type A (GABAA)-mediated inhibition controlled by the developmental up-regulation of the potassium-chloride (K-Cl) cotransporter 2 (KCC2)...