A New Biomechanical Deformation Response Parameter: Change in Central Corneal Thickness During Air Puff Induced Corneal Deformation.

PURPOSE: To investigate the percent change in central corneal thickness (%ΔCCT) during air-puff-induced deformation as an indicator of corneal biomechanical response. METHODS: Forty ex vivo human eyes from forty donors were imaged using the CorVis ST at experimentally controlled intraocular pressure (IOP) of 10, 20, 30, and 40 mmHg, followed by uniaxial strip testing to calculate tensile modulus. The CorVis ST research software tracked the anterior and posterior cornea edges and determined the dynamic corneal response (DCR) parameters. Eyes were excluded if image quality or posterior tracking issues were present. Custom algorithms were used to calculate CCT during deformation using a ray-tracing method to correct for Scheimpflug and optical distortion within each image. Correlation and stepwise regression analyses between the shape-related DCR parameters and %ΔCCT were conducted. A mixed model analysis was performed to test the effect of IOP and the strongest significant predictors of the stepwise regression on %ΔCCT. The significance threshold was set to p < 0.05. RESULTS: Thirty eyes were ultimately analyzed and CCT increased significantly from the pre-deformation state to the highest concavity state at each IOP level (p < 0.001). IOP and multiple shape DCRs were found to be significantly related to %ΔCCT (p < 0.0001). The strongest predictor of %ΔCCT was integrated inverse radius (IIR) (p < 0.0001; partial R2 = 0.4772) with no other parameter having a partial R2 value greater than 0.04. The mixed model analysis showed that IIR was the sole predictor (p = 0.0098) and IOP was no longer significant as a single predictor. However, the interaction of IIR with IOP (p = 0.0023) had a significant effect on %ΔCCT. CONCLUSION: Percent change in CCT is influenced by corneal stiffness as indicated by the significant relationship with IIR. The %ΔCCT may be a potential biomarker for determining differences in corneal deformation response with corneal diseases.

Effects of control temperature, ablation time, and background tissue in radiofrequency ablation of osteoid osteoma: A computer modeling study.

To study the effects of the control temperature, ablation time, and the background tissue surrounding the tumor on the size of the ablation zone on radiofrequency ablation (RFA) of osteoid osteoma (OO). Finite element models of non-cooled temperature-controlled RFA of typical OOs were developed to determine the resulting ablation radius at control temperatures of 70, 80, and 90°C. Three different geometries were used, mimicking common cases of OO. The ablation radius was obtained by using the Arrhenius equation to determine cell viability. Ablation radii were larger for higher temperatures and also increased with time. All geometries and control temperatures tested had ablation radii larger than the tumor. The ablation radius developed rapidly in the first few minutes for all geometries and control temperatures tested, developing slowly towards the end of the ablation. Resistive heating and the temperature distribution showed differences depending on background tissue properties, resulting in differences in the ablation radius on each geometry. The ablation radius has a clear dependency not only on the properties of the tumor but also on the background tissue. Lower background tissue's electrical conductivity and blood perfusion rates seem to result in larger ablation zones. The differences observed between the different geometries suggest the need for patient-specific planning, as the anatomical variations could cause significantly different outcomes where models like the one here presented could help to guarantee safe and successful tumor ablations.

Cntnap4 differentially contributes to GABAergic and dopaminergic synaptic transmission.

Although considerable evidence suggests that the chemical synapse is a lynchpin underlying affective disorders, how molecular insults differentially affect specific synaptic connections remains poorly understood. For instance, Neurexin 1a and 2 (NRXN1 and NRXN2) and CNTNAP2 (also known as CASPR2), all members of the neurexin superfamily of transmembrane molecules, have been implicated in neuropsychiatric disorders. However, their loss leads to deficits that have been best characterized with regard to their effect on excitatory cells. Notably, other disease-associated genes such as BDNF and ERBB4 implicate specific interneuron synapses in psychiatric disorders. Consistent with this, cortical interneuron dysfunction has been linked to epilepsy, schizophrenia and autism. Using a microarray screen that focused upon synapse-associated molecules, we identified Cntnap4 (contactin associated protein-like 4, also known as Caspr4) as highly enriched in developing murine interneurons. In this study we show that Cntnap4 is localized presynaptically and its loss leads to a reduction in the output of cortical parvalbumin (PV)-positive GABAergic (γ-aminobutyric acid producing) basket cells. Paradoxically, the loss of Cntnap4 augments midbrain dopaminergic release in the nucleus accumbens. In Cntnap4 mutant mice, synaptic defects in these disease-relevant neuronal populations are mirrored by sensory-motor gating and grooming endophenotypes; these symptoms could be pharmacologically reversed, providing promise for therapeutic intervention in psychiatric disorders.

Incidence of sexually transmitted infections in HIV-infected and HIV-uninfected adolescents in the USA.

Little is known about the incidence of bacterial sexually transmitted infections (STIs) among HIV-infected versus HIV-uninfected adolescents. This secondary analysis of a national, multisite study included adolescents aged 12-18 years who were behaviourally HIV-infected (n = 346) or HIV-uninfected but at-risk (n = 182). Incidence rates of bacterial STIs (gonorrhoea, chlamydia [CT] and trichomonas [TV; women]) were calculated using Poisson modelling. Factors associated with incident STIs were explored using Cox proportional hazards modelling. HIV-infected versus HIV-uninfected women had higher TV incidence (1.3 versus 0.6/100 person-months; P = 0.002). HIV-uninfected versus HIV-infected women had higher CT incidence (1.6 versus 1.1/100 person-months; P = 0.04). Among women, demographic, behavioural and HIV-related factors were associated with incident STIs. Among men, there were no differences in incident STIs. In this first analysis comparing STI incidence between HIV-infected and HIV-uninfected adolescents, bacterial STI incidence among women significantly differed by HIV status, and factors associated with incident STIs varied by STI and HIV status.

Remote sensing of particulate pollution from space: have we reached the promised land?

The Critical Review of Hoff and Christopher, along with the discussants, provides an important perspective on the interface between satellite measurement science and air quality observations. A top-down picture of the usefulness of satellite observations in terms of air quality regulatory and technical support requirements can be summarized. The air quality requirements are (1) determination of compliance with the ambient air quality standards, (2) inference of human and ecosystem exposure, (3) identification of intra- and intercontinental events relevant to EE, (4) establishment of trends in ambient concentrations relevant to accountability, (5) regulatory and forecast model applications, and (6) extension of fundamental knowledge relevant to air quality. Each of these topics is important to air quality management, and each has detailed technical issues associated with spatial and temporal resolution, accuracy, and precision, etc. In any case, one can summarize the broad capabilities of measurement systems to address these requirements as listed in Table 1. From this rather superficial summary table, investigators should be encouraged to forward increased interaction between the various measurement communities and to facilitate the utility of a comprehensive portfolio of measurements and adjunct analyses for improved air quality applications. The Critical Review has done much to educate air quality scientists on the possibilities for using satellite remote sensing for various purposes. However, space scientists also need a better education on air quality science. Recently published reviews on PM air quality measurements are available that complement the Hoff-Christopher paper on this topic. The need for greater collaboration of air quality and space scientists is evident in an article published in the July issue of the journal. Al-Hamdan et al. provide an interesting and useful analysis of relationships between surface air quality and space-based satellite AOD to estimate human exposure. They obtain mostly urban PM data from EPA's Air Quality System (AQS), but they neglect the potentially more useful PM2.5 and chemical speciation data from the nonurban Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Southeastern Aerosol Research and Characterization (SEARCH) networks. They correlate PM2.5 mass with optical depth, although visibility assessments show that light extinction is better represented by a weighted sum of PM2.5 sulfate, nitrate, organic carbon, elemental carbon, and soil dust. Their comparison of hourly measurements with filter measurements does not specify the source of the hourly values as TEOM or BAM. Spatial outliers for ground-level measurements are removed to improve the correlation of PM2.5 with AOD, although these "outliers" are probably real values that relate to human exposure or a nearby source effect. The point here is not to overly criticize a good publication that will be highly cited. The intent is to demonstrate the value of air quality and space scientists working together more closely on this topic. This is something the review authors alluded to in their review, but if, as they concluded, the "promised land" has not been reached, then perhaps it is an appropriate time for the atmospheric community to ask, "Can near-term satellite observations play a role in characterizing broad-based (outdoor) exposure to pollutants and consequently influence public health improvement?" and, if so, then, "What comprehensive, integrated system is needed if satellite observations are to be used together with ground-based observations and modeling to continue improving air quality management options?"

Developmental changes in the expression of calbindin and potassium-channel subunits Kv3.1b and Kv3.2 in mouse Renshaw cells.

One class of spinal interneurons, the Renshaw cells, is able to discharge at very high frequencies in adult mammals. Neuronal firing at such high frequencies requires voltage-gated potassium channels to rapidly repolarize the membrane potential after each action potential. We sought to establish the pattern of expression of calbindin and potassium channels with Kv3.1b and Kv3.2 subunits in Renshaw cells at different developmental stages of postnatal mice. The pattern of expression of calbindin changed dramatically during early postnatal development. An adult pattern of calbindin reactive neurons started to emerge from postnatal day 10 to postnatal day 14, with cells in laminae I and II of superficial dorsal horn and the ventral lamina VII. Renshaw cells were identified immunohistochemically by their expression of calbindin and their location in the ventral horn of the spinal cord. Western blot results of the lumbar spinal cord showed that Kv3.1b expression became faintly evident from postnatal day 10, reached a maximum at postnatal day 21 and was maintained through postnatal day 49. Double labeling results showed that all Renshaw cells expressed Kv3.1b weakly from postnatal day 14, and strongly at postnatal day 21. Western blot results showed that Kv3.2 expression became detectable in the lumbar cord from postnatal day 12, and increased steadily until reaching an adult level at postnatal day 28. In contrast to the Kv3.1b results, Kv3.2 was not expressed in Renshaw cells, although some neurons located at laminae VIII and VI expressed Kv3.2. We conclude that Renshaw cells express Kv3.1b but not Kv3.2 from postnatal day 14.

Differential subcellular localization of the two alternatively spliced isoforms of the Kv3.1 potassium channel subunit in brain.

Voltage-gated K(+) channels containing pore-forming subunits of the Kv3 subfamily have specific roles in the fast repolarization of action potentials and enable neurons to fire repetitively at high frequencies. Each of the four known Kv3 genes encode multiple products by alternative splicing of 3' ends resulting in the expression of K(+) channel subunits differing only in their C-terminal sequence. The alternative splicing does not affect the electrophysiological properties of the channels, and its physiological role is unknown. It has been proposed that one of the functions of the alternative splicing of Kv3 genes is to produce subunit isoforms with differential subcellular membrane localizations in neurons and differential modulation by signaling pathways. We investigated the role of the alternative splicing of Kv3 subunits in subcellular localization by examining the brain distribution of the two alternatively spliced versions of the Kv3.1 gene (Kv3.1a and Kv3.1b) with antibodies specific for the alternative spliced C-termini. Kv3.1b proteins were prominently expressed in the somatic and proximal dendritic membrane of specific neuronal populations in the mouse brain. The axons of most of these neurons also expressed Kv3.1b protein. In contrast, Kv3.1a proteins were prominently expressed in the axons of some of the same neuronal populations, but there was little to no Kv3.1a protein expression in somatodendritic membrane. Exceptions to this pattern were seen in two neuronal populations with unusual targeting of axonal proteins, mitral cells of the olfactory bulb, and mesencephalic trigeminal neurons, which expressed Kv3.1a protein in dendritic and somatic membrane, respectively. The results support the hypothesis that the alternative spliced C-termini of Kv3 subunits regulate their subcellular targeting in neurons.

Evidence for the presence of a novel Kv4-mediated A-type K(+) channel-modifying factor.

1. Subthreshold-operating transient (A-type) K(+) currents (I(SA)s) are important in regulating neuronal firing frequency and in the modulation of incoming signals in dendrites. It is now known that Kv4 proteins are the principal, or pore-forming, subunits of the channels mediating I(SA)s(.) In addition, accessory subunits of Kv4 channels have also been identified. These either have no effect or slow down the inactivation kinetics of Kv4 channels. However, in many neuronal populations the I(SA) is faster, not slower, than the current generated by channels containing only Kv4 proteins. 2. Evidence is presented for the presence in rat cerebellar mRNA of transcripts encoding a molecular factor, termed KAF, that accelerates the kinetics of Kv4 channels. Size-fractionation of cerebellar mRNA in sucrose gradients separated the high molecular weight mRNAs (4-7 kb) encoding KAF from the low molecular weight ones (1.5-3 kb) encoding factors that slow down the inactivation kinetics of Kv4 channels. The latter were identified as KChIPs using anti-KChIP antisense oligonucleotides. 3. Both anti-KChIP and anti-Kv4 antisense oligonucleotides failed to eliminate KAF's activity from the high molecular weight mRNA fraction, thus suggesting that KAF might be a novel subunit(s) that can contribute to generating native I(SA) channel diversity. 4. The time course of the currents expressed by KAF-modified Kv4 channels resembles more closely the time course of the native I(SA) in cerebellar granule cells.

A role for frequenin, a Ca2+-binding protein, as a regulator of Kv4 K+-currents.

Frequenin, a Ca(2+)-binding protein, has previously been implicated in the regulation of neurotransmission, possibly by affecting ion channel function. Here, we provide direct evidence that frequenin is a potent and specific modulator of Kv4 channels, the principal molecular components of subthreshold activating A-type K(+) currents. Frequenin increases Kv4.2 current amplitudes (partly by enhancing surface expression of Kv4.2 proteins) and it slows the inactivation time course in a Ca(2+)-dependent manner. It also accelerates recovery from inactivation. Closely related Ca(2+)-binding proteins, such as neurocalcin and visinin-like protein (VILIP)-1 have no such effects. Specificity for Kv4 currents is suggested because frequenin does not modulate Kv1.4 or Kv3.4 currents. Frequenin has negligible effects on Kv4.1 current inactivation time course. By using chimeras made from Kv4.2 and Kv4.1 subunits, we determined that the differential effects of frequenin are mediated by means of the Kv4 N terminus. Immunohistochemical analysis demonstrates that frequenin and Kv4.2 channel proteins are coexpressed in similar neuronal populations and have overlapping subcellular localizations in brain. Coimmunoprecipitation experiments demonstrate that a physical interaction occurs between these two proteins in brain membranes. Together, our data provide strong support for the concept that frequenin may be an important Ca(2+)-sensitive regulatory component of native A-type K(+) currents.

Immunology and the REACH study: HIV immunology and preliminary findings. Reaching for Excellence in Adolescent Care and Health.

This review paper presents the immunology findings in human immunodeficiency virus (HIV) infected and uninfected youth in the Reaching for Excellence in Adolescent Care and Health (REACH) Project within the context of basic and HIV immunology concepts. Methods employed in the study for specimen collection, management, and laboratory analysis are presented. This paper reviews published analyses of cross-sectional data; longitudinal analyses are underway. These preliminary data extend the work of others in demonstrating the potential for substantial thymic reserve in youth. This finding in HIV infected adolescents has implications for a fuller response to antiretroviral or immune-based therapies compared to that seen in adults. Dysregulation in mucosal immunity may appear before systemic HIV effects are seen and requires attention particularly to screening and treatment of genital co-infections. REACH has demonstrated gender differences in immunologic measures irrespective of HIV infection status.

Kv3 channels: voltage-gated K+ channels designed for high-frequency repetitive firing.

Analysis of the Kv3 subfamily of K(+) channel subunits has lead to the discovery of a new class of neuronal voltage-gated K(+) channels characterized by positively shifted voltage dependencies and very fast deactivation rates. These properties are adaptations that allow these channels to produce currents that can specifically enable fast repolarization of action potentials without compromising spike initiation or height. The short spike duration and the rapid deactivation of the Kv3 currents after spike repolarization maximize the quick recovery of resting conditions after an action potential. Several neurons in the mammalian CNS have incorporated into their repertoire of voltage-dependent conductances a relatively large number of Kv3 channels to enable repetitive firing at high frequencies - an ability that crucially depends on the special properties of Kv3 channels and their impact on excitability.

KT3.2 and KT3.3, two novel human two-pore K(+) channels closely related to TASK-1.

We report the cloning of human KT3.2 and KT3.3 new members of the two-pore K(+) channel (KT) family. Based on amino acid sequence and phylogenetic analysis, KT3.2, KT3.3, and TASK-1 constitute a subfamily within the KT channel mammalian family. When Xenopus oocytes were injected with KT3.2 cRNA, the resting membrane potential was brought close to the potassium equilibrium potential. At low extracellular K(+) concentrations, two-electrode voltage-clamp recordings revealed the expression of predominantly outward currents. With high extracellular K(+) (98 mM), the current-voltage relationship exhibited weak outward rectification. Measurement of reversal potentials at different [K(+)](o) revealed a slope of 48 mV per 10-fold change in K(+) concentration as expected for a K(+)-selective channel. Unlike TASK-1, which is highly sensitive to changes of pH in the physiological range, KT3.2 currents were relatively insensitive to changes in intracellular or extracellular pH within this range due to a shift in the pH dependency of KT3.2 of 1 pH unit in the acidic direction. On the other hand, the phorbol ester phorbol 12-myristate 13-acetate (PMA), which does not affect TASK-1, produces strong inhibition of KT3.2 currents. Human KT3.2 mRNA expression was most prevalent in the cerebellum. In rat, KT3.2 is exclusively expressed in the brain, but it has a wide distribution within this organ. High levels of expression were found in the cerebellum, medulla, and thalamic nuclei. The hippocampus has a nonhomogeneous distribution, expressing at highest levels in the lateral posterior and inferior portions. Medium expression levels were found in neocortex. The KT3.2 gene is located at chromosome 8q24 1-3, and the KT3.3 gene maps to chromosome 20q13.1.

Different effects of the Ca(2+)-binding protein, KChIP1, on two Kv4 subfamily members, Kv4.1 and Kv4.2.

The Ca(2+)-binding protein, K(+) channel-interacting protein 1 (KChIP1), modulates Kv4 channels. We show here that KChIP1 affects Kv4.1 and Kv4.2 currents differently. KChIP1 slows Kv4.2 inactivation but accelerates the Kv4.1 inactivation time course. Kv4.2 activation is shifted in a hyperpolarizing direction, whereas a depolarizing shift occurs for Kv4.1. On the other hand, KChIP1 increases the current amplitudes and accelerates recovery from inactivation of both currents. An involvement of the Kv4 N-terminus in these differential effects is demonstrated using chimeras of Kv4.2 and Kv4.1. These results reveal a novel interaction of KChIP1 with these two Kv4 members. This represents a mechanism to further increase the functional diversity of K(+) channels.

Differential expression of genes encoding subthreshold-operating voltage-gated K+ channels in brain.

The members of the three subfamilies (eag, erg, and elk) of the ether-a-go-go (EAG) family of potassium channel pore-forming subunits express currents that, like the M-current (I(M)), could have considerable influence on the subthreshold properties of neuronal membranes, and hence the control of excitability. A nonradioactive in situ hybridization (NR-ISH) study of the distribution of the transcripts encoding the eight known EAG family subunits in rat brain was performed to identify neuronal populations in which the physiological roles of EAG channels could be studied. These distributions were compared with those of the mRNAs encoding the components of the classical M-current (Kcnq2 and Kcnq3). NR-ISH was combined with immunohistochemistry to specific neuronal markers to help identify expressing neurons. The results show that each EAG subunit has a specific pattern of expression in rat brain. EAG and Kcnq transcripts are prominent in several types of excitatory neurons in the cortex and hippocampus; however, only one of these channel components (erg1) was consistently expressed in inhibitory interneurons in these areas. Some neuronal populations express more than one product of the same subfamily, suggesting that the subunits may form heteromeric channels in these neurons. Many neurons expressed multiple EAG family and Kcnq transcripts, such as CA1 pyramidal neurons, which contained Kcnq2, Kcnq3, eag1, erg1, erg3, elk2, and elk3. This indicates that the subthreshold current in many neurons may be complex, containing different components mediated by a number of channels with distinct properties and neuromodulatory responses.

Modulation of Kv3 potassium channels expressed in CHO cells by a nitric oxide-activated phosphatase.

1.Voltage-gated K+ channels containing Kv3 subunits play specific roles in the repolarization of action potentials. Kv3 channels are expressed in selective populations of CNS neurons and are thought to be important in facilitating sustained and/or repetitive high frequency firing. Regulation of the activity of Kv3 channels by neurotransmitters could have profound effects on the repetitive firing characteristics of those neurons. 2.Kv3 channels are found in several neuronal populations in the CNS that express nitric oxide synthases (NOSs). We therefore investigated whether Kv3 channels are modulated by the signalling gas nitric oxide (NO). 3. We found that Kv3.1 and Kv3.2 currents are potentially suppressed by D-NONOate and other NO donors. The effects of NO on these currents are mediated by the activation of guanylyl cyclase (GC), since they are prevented by Methylene Blue, an inhibitor of GC, and by ODQ, a specific inhibitor of the soluble form of GC. Moreover, application of 8-Br-cGMP, a permeant analogue of cGMP, also blocked Kv3.1 and Kv3.2 currents. 4.KT5283, a cGMP-dependent protein kinase (PKG) blocker, prevented the inhibition of Kv3.1 and Kv3.2 currents by D-NONOate and 8-Br-cGMP. This indicates that activation of PKG as a result of the increase in intracellular cGMP levels produced by D-NONOate or 8-Br-cGMP is necessary for channel block. 5. Although the effects of NO on Kv3.1 and Kv3.2 channels require PKG activity, two observations suggest that they are not mediated by phosphorylation of channel proteins: (a) the reagents affect both Kv3.2 and Kv3.1 channels, although only Kv3.2 proteins have a putative PKA-PKG phosphorylation site, and (b) mutation of the PKA-PKG phosphorylation site in Kv3.2 does not interfere with the effects of NO or cGMP. 6. The inhibitory effects of NO and cGMP on Kv3.1 and Kv3.2 currents appear to be mediated by the activation of serine-threonine phosphatase, since they are blocked by low doses of okadaic acid. Furthermore, direct intracellular application of the catalytic subunit of protein phosphatase 2A inhibited Kv3.2 currents, indicating that activity of PKG-induced phosphatase is necessary and sufficient to inhibit these channels. 7. The results suggest that basal phosphorylation of Kv3 channel proteins is required for proper channel function. Activation of phosphatases via NO or other signals that increase cGMP might be a potent mechanism to regulate Kv3 channel activity in neurons.

Association between steatorrhea, growth, and immunologic status in children with perinatally acquired HIV infection.

OBJECTIVE: To examine the prevalence of steatorrhea and exocrine pancreatic insufficiency (EPI) and their association with growth and immune status variables in children with perinatally acquired human immunodeficiency virus (HIV) infection. DESIGN: Cross-sectional study. SETTING: Tertiary care HIV subspecialty practice. PARTICIPANTS: Children with perinatally acquired HIV infection. Exclusion criteria included being younger than 1 year and receiving mineral oil as a medication. METHODS: Weight, height, and upper arm anthropometric variables were measured. Spot stool samples were analyzed for steatorrhea using the Sudan III qualitative test and for EPI using fecal elastase-1 enzyme assay. Hormone-stimulated pancreatic function testing and 72-hour stool and dietary fat sample collection were performed when fecal elastase-1 enzyme was in the range of EPI, defined as less than 200 microgram/g. HIV RNA viral load, CD4 status, type of antiretroviral therapy, and biochemical evidence of hepatobiliary disease were measured within 3 months of stool sample collection. z Scores were computed for height, weight, triceps skinfold, and upper arm muscle area. RESULTS: We enrolled 44 patients (23 girls [52%]) with a mean +/- SD age of 7.4 +/- 3.1 years. None had hepatobiliary disease. The prevalence of steatorrhea was 39% (95% confidence interval, 23%-56%). The prevalence of EPI was 0% (95% confidence interval, 0%-9%). There were no associations between steatorrhea and EPI, growth, HIV RNA viral load, CD4 status, or type of antiretroviral therapy. Older children had decreased z scores for height (r = -0.42; P =.006). CONCLUSIONS: The clinical significance of steatorrhea in children with HIV infection is unclear. Furthermore, its evaluation should focus on nonpancreas-based conditions. Continual close monitoring of growth is essential in children with HIV infection.

Impaired fast-spiking, suppressed cortical inhibition, and increased susceptibility to seizures in mice lacking Kv3.2 K+ channel proteins.

Voltage-gated K(+) channels of the Kv3 subfamily have unusual electrophysiological properties, including activation at very depolarized voltages (positive to -10 mV) and very fast deactivation rates, suggesting special roles in neuronal excitability. In the brain, Kv3 channels are prominently expressed in select neuronal populations, which include fast-spiking (FS) GABAergic interneurons of the neocortex, hippocampus, and caudate, as well as other high-frequency firing neurons. Although evidence points to a key role in high-frequency firing, a definitive understanding of the function of these channels has been hampered by a lack of selective pharmacological tools. We therefore generated mouse lines in which one of the Kv3 genes, Kv3.2, was disrupted by gene-targeting methods. Whole-cell electrophysiological recording showed that the ability to fire spikes at high frequencies was impaired in immunocytochemically identified FS interneurons of deep cortical layers (5-6) in which Kv3.2 proteins are normally prominent. No such impairment was found for FS neurons of superficial layers (2-4) in which Kv3.2 proteins are normally only weakly expressed. These data directly support the hypothesis that Kv3 channels are necessary for high-frequency firing. Moreover, we found that Kv3.2 -/- mice showed specific alterations in their cortical EEG patterns and an increased susceptibility to epileptic seizures consistent with an impairment of cortical inhibitory mechanisms. This implies that, rather than producing hyperexcitability of the inhibitory interneurons, Kv3.2 channel elimination suppresses their activity. These data suggest that normal cortical operations depend on the ability of inhibitory interneurons to generate high-frequency firing.