Sinteza N4-(2,4-dimetilfenil) semikarbazona kao inhibitori 4-aminobutirat aminotransferaze

Several 2,4-dimethylphenyl substituted semicarbazones were synthesized in three steps involving aryl urea and aryl semicarbazide formations. The structures were confirmed by spectral and elemental analyses. All the compounds were evaluated for anticonvulsant activity by using a series of test models including maximal electroshock seizure (MES), subcutaneous pentylenetetrazole (scPTZ) and subcutaneous strychnine (scSTY) seizure threshold tests. The compounds were also evaluated for behavioural impairement and depression activity. In the neurochemical investigation, potent compounds were evaluated for their effects on rat brain -aminobutyric acid levels and in vitro -aminobutyrate transaminase (Pseudomonas fluorescens) activity. Preliminary studies suggest these compounds to exhibit anticonvulsant activity via GABA-mediated mechanism.Sintetizirano je nekoliko 2,4-dimetilfenil supstituiranih semikarbazona u tri sintetska koraka koji uključuju aril uree i aril semikarbazide. Strukture spojeva su potvrđene spektroskopskim metoda i elementarnom analizom. Ispitano je antikonvulzivno djelovanje novih spojeva nakon izazivanja konvulzija elektrošokom te supkutanom primjenom pentilentetrazola ili strihnina. Osim toga, testirano je antidepresivno djelovanje te učinak tih spojeva na ponašanje štakora. Praćen je njihov utjecaj na koncentraciju gama-aminomaslačne kiseline (GABA) u mozgu štakora te in vitro na aktivnost gama-aminobutirat transaminaze (Pseudomonas fluorescens). Preliminarni pokusi ukazuju da antikonvulzivno djelovanje ovih spojeva uključuje GABA-ergički sustav

Structural and functional properties of subsidiary atrial pacemakers in a goat model of sinus node disease

Background: The sinoatrial/sinus node (SAN) is the primary pacemaker of the heart. In humans, SAN is surrounded by the paranodal area (PNA). Although the PNA function remains debated, it is thought to act as a subsidiary atrial pacemaker (SAP) tissue and become the dominant pacemaker in the setting of sinus node disease (SND). Large animal models of SND allow characterization of SAP, which might be a target for novel treatment strategies for SAN diseases.Methods: A goat model of SND was developed (n = 10) by epicardially ablating the SAN and validated by mapping of emergent SAP locations through an ablation catheter and surface electrocardiogram (ECG). Structural characterization of the goat SAN and SAP was assessed by histology and immunofluorescence techniques.Results: When the SAN was ablated, SAPs featured a shortened atrioventricular conduction, consistent with the location in proximity of atrioventricular junction. SAP recovery time showed significant prolongation compared to the SAN recovery time, followed by a decrease over a follow-up of 4 weeks. Like the SAN tissue, the SAP expressed the main isoform of pacemaker hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) and Na+/Ca2+ exchanger 1 (NCX1) and no high conductance connexin 43 (Cx43). Structural characterization of the right atrium (RA) revealed that the SAN was located at the earliest activation [i.e., at the junction of the superior vena cava (SVC) with the RA] and was surrounded by the paranodal-like tissue, extending down to the inferior vena cava (IVC). Emerged SAPs were localized close to the IVC and within the thick band of the atrial muscle known as the crista terminalis (CT).Conclusions: SAN ablation resulted in the generation of chronic SAP activity in 60% of treated animals. SAP displayed development over time and was located within the previously discovered PNA in humans, suggesting its role as dominant pacemaker in SND. Therefore, SAP in goat constitutes a promising stable target for electrophysiological modification to construct a fully functioning pacemaker

Anger, emotion, and arrhythmias: from brain to heart

Strong emotion and mental stress are now recognized as playing a significant role in severe and fatal ventricular arrhythmias. The mechanisms, although incompletely understood, include central processing at the cortical and brain stem level, the autonomic nerves and the electrophysiology of the myocardium. Each of these is usually studied separately by investigators from different disciplines. However, many are regulatory processes which incorporate interactive feedforward and feedback mechanisms. In this review we consider the whole as an integrated interactive brain–heart system

Spontaneous and electrically evoked Ca2+ transients in cardiomyocytes of the rat pulmonary vein

The pulmonary vein is surrounded by an external sleeve of cardiomyocytes that are widely recognised to play an important role in atrial fibrillation. While intracellular Ca2+ is thought to influence the electrical activity of cardiomyocytes, there have been relatively few studies examining Ca2+ signalling in these cells. Therefore, using fluo-4 and fluorescence imaging microscopy, we have investigated Ca2+ signalling in an intact section of the rat pulmonary vein. Under resting conditions cardiomyocytes displayed spontaneous Ca2+ transients, which were variable in amplitude and had a frequency of 1.6±0.03 Hz. The Ca2+ transients were asynchronous amongst neighbouring cardiomyocytes and tended to propagate throughout the cell as a wave. Removing extracellular Ca2+ produced a slight reduction in the amplitude and frequency of the spontaneous Ca2+ transients; however, ryanodine (20M) had a much greater effect on the amplitude and reduced the frequency by 94±2%. Blocking IP3 receptors with 2-aminoethoxydiphenyl borate (20M) also reduced the amplitude and frequency (by 73±11%) of these events, indicating the importance of Ca2+ release from the SR. Electrical field stimulation of the pulmonary vein produced Ca2+ transients in cardiomyocytes that were significantly reduced by either voltage-gated Ca2+ channel blockers or ryanodine

From the Purkinje fibres to the ventricle:One dimensional computer simulation for the healthy and failing heart

This study used one-dimensional computer simulation to investigate the influence of heart failure on action potential conduction through the left Purkinje fibres to the left ventricle. The study was based on a rabbit model of left ventricular heart failure caused by volume and pressure overload. To simulate the effect of heart failure, we began with models of the healthy rabbit Purkinje fibre action potential and healthy left ventricular (endocardial) action potential. In the absence of ionic current measurements from failing rabbit Purkinje fibres, we assumed that changes in ionic currents mirrored changes in ion channel expression (measured at the messenger RNA level): ionic conductances were adjusted based on changes in expression of the relevant ion channels. Ionic currents in the left ventricle were adjusted in the same way, but in addition, changes in ionic currents measured in the failing rabbit left ventricle by Ruijter et al. and Powizd et al. were used in simulations. The simulations predict a gradient in action potential duration from the Purkinje fibres to the ventricle and this gradient is exacerbated in heart failure. The predicted changes in the Purkinje fibre and left ventricular action potential were compared to actual changes measured using sharp microelectrodes.</p