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.

K(+) channel expression distinguishes subpopulations of parvalbumin- and somatostatin-containing neocortical interneurons

Kv3.1 and Kv3.2 K+ channel proteins form similar voltage-gated K+ channels with unusual properties, including fast activation at voltages positive to −10 mV and very fast deactivation rates. These properties are thought to facilitate sustained high-frequency firing. Kv3.1 subunits are specifically found in fast-spiking, parvalbumin (PV)-containing cortical interneurons, and recent studies have provided support for a crucial role in the generation of the fast-spiking phenotype. Kv3.2 mRNAs are also found in a small subset of neocortical neurons, although the distribution of these neurons is different. We raised antibodies directed against Kv3.2 proteins and used dual-labeling methods to identify the neocortical neurons expressing Kv3.2 proteins and to determine their subcellular localization. Kv3.2 proteins are prominently expressed in patches in somatic and proximal dendritic membrane as well as in axons and presynaptic terminals of GABAergic interneurons. Kv3.2 subunits are found in all PV-containing neurons in deep cortical layers where they probably form heteromultimeric channels with Kv3.1 subunits. In contrast, in superficial layer PV-positive neurons Kv3.2 immunoreactivity is low, but Kv3.1 is still prominently expressed. Because Kv3.1 and Kv3.2 channels are differentially modulated by protein kinases, these results raise the possibility that the fast-spiking properties of superficial- and deep-layer PV neurons are differentially regulated by neuromodulators. Interestingly, Kv3.2 but not Kv3.1 proteins are also prominent in a subset of seemingly non-fast-spiking, somatostatin- and calbindin-containing interneurons, suggesting that the Kv3.1–Kv3.2 current type can have functions other than facilitating high-frequency firing.

Motivational effects of cannabinoids are mediated by μ-opioid and k-opioid receptor

Repeated THC administration produces motivational and somaticadaptive changes leading to dependence in rodents. Toinvestigate the molecular basis for cannabinoid dependenceand its possible relationship with the endogenous opioid system,we explored Δ9-tetrahydrocannabinol (THC) activity in mice lacking μ-, δ- or κ-opioid receptor genes. Acute THCinduced hypothermia, antinociception, and ypolocomotion remained unaffected in these mice, whereas THC tolerance and withdrawal were minimally modified in mutant animals. In contrast, profound phenotypic changes are observed in several place conditioning protocols that reveal both THC rewarding and aversive properties. Absence of μ receptors abolishes THC place preference. Deletion of κ receptors ablates THC place aversion and furthermore unmasks THC place preference. Thus, an opposing activity of μ- and κ-opioid receptors in modulating reward pathways forms the basis for the dual euphoric–dysphoric activity of THC.

Impact of recommendation updates in well-controlled patients on nonrecommended antiretroviral therapies: the Swiss HIV cohort study.

BACKGROUND: HIV treatment recommendations are updated as clinical trials are published. Whether recommendations drive clinicians to change antiretroviral therapy in well-controlled patients is unexplored. METHODS: We selected patients with undetectable viral loads (VLs) on nonrecommended regimens containing double-boosted protease inhibitors (DBPIs), triple-nucleoside reverse transcriptase inhibitors (NRTIs), or didanosine (ddI) plus stavudine (d4T) at publication of the 2006 International AIDS Society recommendations. We compared demographic and clinical characteristics with those of control patients with undetectable VL not on these regimens and examined clinical outcome and reasons for treatment modification. RESULTS: At inclusion, 104 patients were in the DBPI group, 436 in the triple-NRTI group, and 19 in the ddI/d4T group. By 2010, 28 (29%), 204 (52%), and 1 (5%) patient were still on DBPIs, triple-NRTIs, and ddI plus d4T, respectively. 'Physician decision,' excluding toxicity/virological failure, drove 30% of treatment changes. Predictors of recommendation nonobservance included female sex [adjusted odds ratio (aOR) 2.69, 95% confidence interval (CI) 1 to 7.26; P = 0.01] for DPBIs, and undetectable VL (aOR 3.53, 95% CI 1.6 to 7.8; P = 0.002) and lack of cardiovascular events (aOR 2.93, 95% CI 1.23 to 6.97; P = 0.02) for triple-NRTIs. All patients on DBPIs with documented diabetes or a cardiovascular event changed treatment. Recommendation observance resulted in lower cholesterol values in the DBPI group (P = 0.06), and more patients having undetectable VL (P = 0.02) in the triple-NRTI group. CONCLUSION: The physician's decision is the main factor driving change from nonrecommended to recommended regimens, whereas virological suppression is associated with not switching. Positive clinical outcomes observed postswitch underline the importance of observing recommendations, even in well-controlled patients.

Right coronary artery flow velocity and volume assessment with spiral K-space sampled breathhold velocity-encoded MRI at 3 tesla: accuracy and reproducibility.

PURPOSE: To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity-encoded (VE) MRI with spiral k-space sampling at 3 Tesla. MATERIALS AND METHODS: Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 +/- 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA). RESULTS: MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. CONCLUSION: 3T breathhold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

[Archives de la Parole]. , La parabole de l'enfant prodigue : récit (dravidien, malayālam, province de Madras) / [Sir George Grierson], éd. ; Linguistic survey of India ; [C.K. Gopalamenon], voix

[Traditions. Asie. Inde. Province de Madras [i.e. Chennai]. État du Kérala. Région du Malabar]