Kv2.1 channels play opposing roles in regulating membrane potential, Ca2+ channel function, and myogenic tone in arterial smooth muscle.

The accepted role of the protein Kv2.1 in arterial smooth muscle cells is to form K+ channels in the sarcolemma. Opening of Kv2.1 channels causes membrane hyperpolarization, which decreases the activity of L-type CaV1.2 channels, lowering intracellular Ca2+ ([Ca2+]i) and causing smooth muscle relaxation. A limitation of this model is that it is based exclusively on data from male arterial myocytes. Here, we used a combination of electrophysiology as well as imaging approaches to investigate the role of Kv2.1 channels in male and female arterial myocytes. We confirmed that Kv2.1 plays a canonical conductive role but found it also has a structural role in arterial myocytes to enhance clustering of CaV1.2 channels. Less than 1% of Kv2.1 channels are conductive and induce membrane hyperpolarization. Paradoxically, by enhancing the structural clustering and probability of CaV1.2-CaV1.2 interactions within these clusters, Kv2.1 increases Ca2+ influx. These functional impacts of Kv2.1 depend on its level of expression, which varies with sex. In female myocytes, where expression of Kv2.1 protein is higher than in male myocytes, Kv2.1 has conductive and structural roles. Female myocytes have larger CaV1.2 clusters, larger [Ca2+]i, and larger myogenic tone than male myocytes. In contrast, in male myocytes, Kv2.1 channels regulate membrane potential but not CaV1.2 channel clustering. We propose a model in which Kv2.1 function varies with sex: in males, Kv2.1 channels control membrane potential but, in female myocytes, Kv2.1 plays dual electrical and CaV1.2 clustering roles. This contributes to sex-specific regulation of excitability, [Ca2+]i, and myogenic tone in arterial myocytes

Nanodiamonds-induced effects on neuronal firing of mouse hippocampal microcircuits

Fluorescent nanodiamonds (FND) are carbon-based nanomaterials that can efficiently incorporate optically active photoluminescent centers such as the nitrogen-vacancy complex, thus making them promising candidates as optical biolabels and drug-delivery agents. FNDs exhibit bright fluorescence without photobleaching combined with high uptake rate and low cytotoxicity. Focusing on FNDs interference with neuronal function, here we examined their effect on cultured hippocampal neurons, monitoring the whole network development as well as the electrophysiological properties of single neurons. We observed that FNDs drastically decreased the frequency of inhibitory (from 1.81 Hz to 0.86 Hz) and excitatory (from 1.61 Hz to 0.68 Hz) miniature postsynaptic currents, and consistently reduced action potential (AP) firing frequency (by 36%), as measured by microelectrode arrays. On the contrary, bursts synchronization was preserved, as well as the amplitude of spontaneous inhibitory and excitatory events. Current-clamp recordings revealed that the ratio of neurons responding with AP trains of high-frequency (fast-spiking) versus neurons responding with trains of low-frequency (slow-spiking) was unaltered, suggesting that FNDs exerted a comparable action on neuronal subpopulations. At the single cell level, rapid onset of the somatic AP ("kink") was drastically reduced in FND-treated neurons, suggesting a reduced contribution of axonal and dendritic components while preserving neuronal excitability.Comment: 34 pages, 9 figure

The human channel gating–modifying A749G CACNA1D (Cav1.3) variant induces a neurodevelopmental syndrome–like phenotype in mice

Germline de novo missense variants of the CACNA1D gene, encoding the pore-forming α1 subunit of Cav1.3 L-type Ca2+ channels (LTCCs), have been found in patients with neurodevelopmental and endocrine dysfunction, but their disease-causing potential is unproven. These variants alter channel gating, enabling enhanced Cav1.3 activity, suggesting Cav1.3 inhibition as a potential therapeutic option. Here we provide proof of the disease-causing nature of such gating-modifying CACNA1D variants using mice (Cav1.3AG) containing the A749G variant reported de novo in a patient with autism spectrum disorder (ASD) and intellectual impairment. In heterozygous mutants, native LTCC currents in adrenal chromaffin cells exhibited gating changes as predicted from heterologous expression. The A749G mutation induced aberrant excitability of dorsomedial striatum–projecting substantia nigra dopamine neurons and medium spiny neurons in the dorsal striatum. The phenotype observed in heterozygous mutants reproduced many of the abnormalities described within the human disease spectrum, including developmental delay, social deficit, and pronounced hyperactivity without major changes in gross neuroanatomy. Despite an approximately 7-fold higher sensitivity of A749G-containing channels to the LTCC inhibitor isradipine, oral pretreatment over 2 days did not rescue the hyperlocomotion. Cav1.3AG mice confirm the pathogenicity of the A749G variant and point toward a pathogenetic role of altered signaling in the dopamine midbrain system

The Organization of the Sinoatrial Node Microvasculature Varies Regionally to Match Local Myocyte Excitability.

The cardiac cycle starts when an action potential is produced by pacemaking cells in the sinoatrial node. This cycle is repeated approximately 100 000 times in humans and 1 million times in mice per day, imposing a monumental metabolic demand on the heart, requiring efficient blood supply via the coronary vasculature to maintain cardiac function. Although the ventricular coronary circulation has been extensively studied, the relationship between vascularization and cellular pacemaking modalities in the sinoatrial node is poorly understood. Here, we tested the hypothesis that the organization of the sinoatrial node microvasculature varies regionally, reflecting local myocyte firing properties. We show that vessel densities are higher in the superior versus inferior sinoatrial node. Accordingly, sinoatrial node myocytes are closer to vessels in the superior versus inferior regions. Superior and inferior sinoatrial node myocytes produce stochastic subthreshold voltage fluctuations and action potentials. However, the intrinsic action potential firing rate of sinoatrial node myocytes is higher in the superior versus inferior node. Our data support a model in which the microvascular densities vary regionally within the sinoatrial node to match the electrical and Ca2+ dynamics of nearby myocytes, effectively determining the dominant pacemaking site within the node. In this model, the high vascular density in the superior sinoatrial node places myocytes with metabolically demanding, high-frequency action potentials near vessels. The lower vascularization and electrical activity of inferior sinoatrial node myocytes could limit these cells to function to support sinoatrial node periodicity with sporadic voltage fluctuations via a stochastic resonance mechanism

INSIDIE DIAGNOSTICHE DELLA TROMBOSI VENOSA CEREBRALE: STORIA DI UN CASO CLINICO

Introduzione: la trombosi venosa cerebrale (TVC) \ue8 una condizione rara, le manifestazioni sono spesso elusive, i primi reperti radiologici non d\u2018immediato riscontro e quindi trascurabili. La prognosi neurologica \ue8 variabile ma nell'80% dei casi \ue8 favorevole. Incidenza: 7 bambini milione/anno. Clinica: cefalea improvvisa, convulsioni, coma, alterazioni oculari i pi\uf9 frequenti. I fattori di rischio, in accordo con la triade di Virchow: trombofilia congenita o acquisita, danno endoteliale (es: flogosi, infezioni) e stasi del flusso sanguigno (es: policitemia). Diagnosi: anamnesi, esame obiettivo, Rm cerebrale, in alternativa eseguire la TC encefalo, se queste negative pu\uf2 essere utile un'angiografia cerebrale. Terapia: nella fase acuta stabilizzare le condizioni del paziente e prevenire o ridurre l'erniazione cerebrale, somministrando mannitolo ev; in alternativa rimozione chirurgica dell'infarto cerebrale o decompressione mediante emicraniectomia, successivamente va trattata la patologia di base e impostata un'accurata terapia anticoagulante. Caso clinico: maschio, 5 anni, storia di autismo, giunge per anemia grave trattata con trasfusione di emazie concentrate. Durante il ricovero comparsa di cefalea e stato soporoso, esegue TC encefalo senza mdc con riscontro di centimetrica iperdensit\ue0 (60 HU circa) in corrispondenza del seno sagittale superiore; all'Angio-RM: trombosi a carico del terzo medio del seno sagittale superiore al vertice ed in corrispondenza della sua porzione pi\uf9 distale, del seno trasverso e del seno sigmoideo di destra. Consulenza oculistica negativa. Esami ematochimici: indici di flogosi e funzionalit\ue0 epato-renale nella norma, D-Dimero 2,92 (vn <0,5), PT, aPTT e INR nella norma, studio trombofilico ancora in corso. Dopo consulto specialistico multidisciplinare inizia terapia con eparina a 100 U/Kg ogni 12 h per 10 giorni e profilassi con acido acetilsalicilico a 10mg/Kg per 3 mesi con progressivo miglioramento delle condizioni cliniche generali e delle performances neurologiche. Il piccolo \ue8 seguito in regime di follow-up ambulatoriale. Conclusioni: la visualizzazione diretta della TVC, nella TC encefalo senza mdc, \ue8 spesso difficile e si sospetta qualora la densit\ue0 delle vene cerebrali appare incrementata rispetto alla loro fisiologica leggera iperdensit\ue0 (dense clot signe). Questa pu\uf2 essere confermata in TC con mdc che determina un enhancement durale attorno al trombo che non ha impregnazione (empty delta sign). Il caso presentato \ue8 una trombosi dei seni sagittale superiore, trasverso e sigmoideo di destra in paziente affetto da autismo; sebbene siano condizioni rare e di difficile interpretazione, vanno sempre sospettate in presenza di alterazioni neurologiche aspecifiche, diagnosticate e trattate prontamente per ridurre la probabilit\ue0 di esito infausto o sequele neurologiche a lungo termine