Electrophysiological properties of neurons in the rat subiculum in vitro

1993 ◽  
Vol 96 (2) ◽  
Author(s):  
JeffreyS. Taube
Keyword(s):  
Electrophysiological Properties

scholarly journals Two Drosophila Innexins Are Expressed in Overlapping Domains and Cooperate to Form Gap-Junction Channels

2000 ◽  
Vol 11 (7) ◽  
pp. 2459-2470 ◽  
Author(s):  
Lucy A. Stebbings ◽  
Martin G. Todman ◽  
Pauline Phelan ◽  
Jonathan P. Bacon ◽  
Jane A. Davies
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Ectopic Expression ◽  
In Vivo Studies ◽  
Electrophysiological Properties ◽  
Gap Junction Channels ◽  
Overlapping Domains ◽  
In Vitro Data

Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes,Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notably in epidermal cells bordering each segment. We also explore the gap-junction–forming capabilities of the encoded proteins. In pairedXenopus oocytes, the injection of Dm-inx2mRNA results in the formation of voltage-sensitive channels in only ∼ 40% of cell pairs. In contrast, Dm-Inx3 never forms channels. Crucially, when both mRNAs are coexpressed, functional channels are formed reliably, and the electrophysiological properties of these channels distinguish them from those formed by Dm-Inx2 alone. We relate these in vitro data to in vivo studies. Ectopic expression ofDm-inx2 in vivo has limited effects on the viability ofDrosophila, and animals ectopically expressingDm-inx3 are unaffected. However, ectopic expression of both transcripts together severely reduces viability, presumably because of the formation of inappropriate gap junctions. We conclude that Dm-Inx2 and Dm-Inx3, which are expressed in overlapping domains during embryogenesis, can form oligomeric gap-junction channels.

Electrophysiological properties and cholinergic responses of rat ventral oral pontine reticular neurons in vitro

1997 ◽  
Vol 754 (1-2) ◽  
pp. 1-11 ◽  
Author(s):  
Angel Núñez ◽  
Carmen De la Roza ◽  
Margarita L Rodrigo-Angulo ◽  
Washington Buño ◽  
Fernando Reinoso-Suárez
Keyword(s):  
Electrophysiological Properties ◽  
Reticular Neurons

scholarly journals Tissue engineering of functional cardiac muscle: molecular, structural, and electrophysiological studies

2001 ◽  
Vol 280 (1) ◽  
pp. H168-H178 ◽  
Author(s):  
M. Papadaki ◽  
N. Bursac ◽  
R. Langer ◽  
J. Merok ◽  
G. Vunjak-Novakovic ◽  
...  
Keyword(s):  
Cardiac Muscle ◽  
Cardiac Myocytes ◽  
Conduction Velocity ◽  
Capture Rate ◽  
Signal Amplitude ◽  
Model System ◽  
Neonatal Rat ◽  
Excitation Threshold ◽  
Electrophysiological Properties

The primary aim of this study was to relate molecular and structural properties of in vitro reconstructed cardiac muscle with its electrophysiological function using an in vitro model system based on neonatal rat cardiac myocytes, three-dimensional polymeric scaffolds, and bioreactors. After 1 wk of cultivation, we found that engineered cardiac muscle contained a 120- to 160-μm-thick peripheral region with cardiac myocytes that were electrically connected through gap junctions and sustained macroscopically continuous impulse propagation over a distance of 5 mm. Molecular, structural, and electrophysiological properties were found to be interrelated and depended on specific model system parameters such as the tissue culture substrate, bioreactor, and culture medium. Native tissue and the best experimental group (engineered cardiac muscle cultivated using laminin-coated scaffolds, rotating bioreactors, and low-serum medium) were comparable with respect to the conduction velocity of propagated electrical impulses and spatial distribution of connexin43. Furthermore, the structural and electrophysiological properties of the engineered cardiac muscle, such as cellularity, conduction velocity, maximum signal amplitude, capture rate, and excitation threshold, were significantly improved compared with our previous studies.

Rate-dependent shortening of action potential duration increases ventricular vulnerability in failing rabbit heart

2011 ◽  
Vol 300 (2) ◽  
pp. H565-H573 ◽  
Author(s):  
Masahide Harada ◽  
Yukiomi Tsuji ◽  
Yuko S. Ishiguro ◽  
Hiroki Takanari ◽  
Yusuke Okuno ◽  
...  
Keyword(s):  
Action Potential ◽  
High Frequency ◽  
Rabbit Heart ◽  
Left Ventricular ◽  
High Frequency Stimulation ◽  
Electrophysiological Properties ◽  
Rate Dependent ◽  
Frequency Stimulation ◽  
And Control

Congestive heart failure (CHF) predisposes to ventricular fibrillation (VF) in association with electrical remodeling of the ventricle. However, much remains unknown about the rate-dependent electrophysiological properties in a failing heart. Action potential properties in the left ventricular subepicardial muscles during dynamic pacing were examined with optical mapping in pacing-induced CHF ( n = 18) and control ( n = 17) rabbit hearts perfused in vitro. Action potential durations (APDs) in CHF were significantly longer than those observed for controls at basic cycle lengths (BCLs) >1,000 ms but significantly shorter at BCLs <400 ms. Spatial APD dispersions were significantly increased in CHF versus control (by 17–81%), and conduction velocity was significantly decreased in CHF (by 6–20%). In both groups, high-frequency stimulation (BCLs <150 ms) always caused spatial APD alternans; spatially concordant alternans and spatially discordant alternans (SDA) were induced at 60% and 40% in control, respectively, whereas 18% and 82% in CHF. SDA in CHF caused wavebreaks followed by reentrant excitations, giving rise to VF. Incidence of ventricular tachycardia/VFs elicited by high-frequency dynamic pacing (BCLs <150 ms) was significantly higher in CHF versus control (93% vs. 20%). In CHF, left ventricular subepicardial muscles show significant APD shortenings at short BCLs favoring reentry formations following wavebreaks in association with SDA. High-frequency excitation itself may increase the vulnerability to VF in CHF.

scholarly journals Optogenetic currents in myofibroblasts acutely alter electrophysiology and conduction of co-cultured cardiomyocytes

2020 ◽  
Author(s):  
Geran Kostecki ◽  
Yu Shi ◽  
Christopher Chen ◽  
Daniel H. Reich ◽  
Emilia Entcheva ◽  
...  
Keyword(s):  
Cardiac Tissue ◽  
Cardiac Injury ◽  
Neonatal Rat ◽  
Culture Studies ◽  
Electrophysiological Properties ◽  
Inward Currents ◽  
Life Threatening ◽  
Cultured Cardiomyocytes ◽  
Cardiac Myofibroblasts

AbstractInteractions between cardiac myofibroblasts and myocytes may slow conduction after cardiac injury, increasing the chance of life-threatening arrhythmia. While co-culture studies have shown that myofibroblasts can affect cardiomyocyte electrophysiology in vitro, the mechanism(s) remain debatable. In this study, primary neonatal rat cardiac myofibroblasts were transduced with the light-activated ion channel Channelrhodopsin-2, which allowed acute and selective modulation of myofibroblast currents in co-cultures with cardiomyocytes. Optical mapping revealed that myofibroblast-specific optogenetically induced inward currents decreased conduction velocity in the co-cultures by 27±6% (baseline = 17.7±5.3 cm/s), and shortened the cardiac action potential duration by 14±7% (baseline = 161±11 ms) when 0.017 mW/mm2 light was applied. When light irradiance was increased to 0.057 mW/mm2, the myofibroblast currents led to spontaneous beating in 6/7 co-cultures. Experiments showed that optogenetic perturbation did not lead to changes in myofibroblast strain and force generation, suggesting purely electrical effects in this model. In silico modeling of optogenetically modified myofibroblast-cardiomyocyte co-cultures largely reproduced these results and enabled a comprehensive study of relevant parameters. These results clearly demonstrate that myofibroblasts are sufficiently electrically connected to cardiomyocytes to effectively alter macroscopic electrophysiological properties in this model of cardiac tissue.

Abstract 386: Notch1 Signaling Negatively Modulates Repolarizing Kv Currents in Cardiomyocytes

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Giulia Borghetti ◽  
Sergio Signore ◽  
Andrea Sorrentino ◽  
Polina Goichberg ◽  
Marcello Rota
Keyword(s):  
Patch Clamp ◽  
Notch Signaling ◽  
Splice Variants ◽  
Postnatal Life ◽  
Wild Type ◽  
Early Postnatal Development ◽  
Electrophysiological Properties ◽  
Notch1 Signaling ◽  
Developing Heart

Notch1 is a critical signaling pathway during embryonic and early postnatal development and activity of this transduction system gradually declines after birth. Conversely, outward K + Kv currents are progressively increased in myocytes during postnatal life leading to shortening of the action potential (AP) duration and acquisition of the mature electrical phenotype. Thus, we tested the possibility that Notch1 signaling modulates the electrophysiological properties of developing cells by interfering with Kv current densities. For this purpose, molecular and physiological studies were conducted in vitro using mouse neonatal myocytes (NMs). These assays were complemented with tests in adult cells obtained from a conditional mouse model of Notch1 intracellular domain (NICD) overexpression. NMs were treated with a γ-secretase inhibitor (DAPT) to prevent the cleavage of Notch1 receptor and subsequent translocation of the active NICD to the nucleus. By RT-PCR, Notch1 targets Hes1 and Hey1 were reduced with DAPT-treatment, confirming the effective perturbation of Notch1 signaling. Importantly, inhibition of Notch signaling led to upregulation of the three splice variants of the Kv channel-interacting proteins 2 (KChIP2) gene, which controls the appearance of outward Kv currents in myocytes. By patch-clamp, Kv currents were identified in only 15% of NMs (n=20) cultured for 1-2 days in in control condition, whereas this fraction increased to 50% (n=18) in cells treated with DAPT. Thus, Notch inhibition promotes the expression of KChIP2 and appearance of Kv currents. To clarify these in vitro findings, the consequences of ectopic activation of Notch1 signaling on the electrical behavior of adult myocytes were established. By patch-clamp, NICD-overexpressing myocytes presented a >2-fold longer duration of the early repolarization phase of the AP, with respect to cells from wild type hearts. This alteration was coupled with a >50% reduction of Kv currents I to and I Kslow1 in NICD-overexpressing cells, with respect to wild-type myocytes. Thus, Notch signaling represses KChIP2 and Kv currents in cardiomyocytes representing an important modulator of the electrical phenotype of the developing heart.

Electrophysiological evidence for Cl secretion in shark renal proximal tubules

1985 ◽  
Vol 248 (2) ◽  
pp. F282-F295 ◽  
Author(s):  
K. W. Beyenbach ◽  
E. Fromter
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
In Vitro Perfusion ◽  
Electrophysiological Properties ◽  
Electrophysiological Responses ◽  
Tubule Lumen ◽  
Transepithelial Voltage ◽  
Cl Conductance

The electrophysiology of shark proximal tubules (Squalus acanthias) was investigated using conventional microelectrodes and cable analysis. Under in vitro perfusion with symmetrical Ringer solutions, tubule transepithelial resistance was 36.3 +/- 2.3 omega X cm2 (means +/- SE, n = 44). Other electrophysiological variables varied widely under control conditions. In unstimulated tubules (n = 16) the transepithelial voltage (VT,o) was lumen positive (1.2 +/- 0.2 mV), the basolateral membrane potential (Vbl,x) was -61.3 +/- 1.6 mV, and the fractional resistance of the apical membrane (fRa) was 0.67 +/- 0.02. Spontaneously stimulated tubules (n = 28) had lumen-negative VT,o values (-1.5 +/- 0.4 mV), low Vbl,x values (-41.3 +/- 1.7 mV), and low fRa values (0.30 +/- 0.02). The stimulated state can be induced in unstimulated tubules via treatment with cAMP. Multiple microelectrode impalements in a single tubule revealed epithelial cells sharing similar electrophysiological properties. Selective ion substitutions in the tubule lumen and peritubular bath uncovered an increased Cl conductance in the apical membrane of spontaneously and cAMP-stimulated tubules. Anthracene-9-carboxylic acid tended to reverse the stimulated state, and furosemide hyperpolarized Vbl,x. These results constitute the first evidence for secretory Cl transport in a renal proximal tubule. The electrophysiological responses to ion substitutions, stimulators, and inhibitors are strikingly similar to those of known Cl-transporting epithelia.

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