Micro-Electrocardiograms to Study Post-Ventricular Amputation of Zebrafish Heart

Abstract

The zebrafish (Danio rerio) is an emerging model for cardiovascular research. The zebrafish heart regenerates after 20% ventricular amputation. However, assessment of the physiological responses during heart regeneration has been hampered by the small size of the heart and the necessity of conducting experiments in an aqueous environment. We developed a methodology to monitor a real-time surface electrocardiogram (ECG) by the use of micro-electrodes, signal amplification, and a low pass-filter at a sampling rate of 1 kHz. Wavelet transform was used to further remove ambient noises. Rather than paralyzing the fish, we performed mild sedation by placing the fish in a water bath mixed with MS-222 (tricane methanesulfonate). We recorded distinct P waves for atrial contraction, QRS complexes for ventricular depolarization, and QT intervals for ventricular repolarization prior to, and 2 and 4 days post-amputation (dpa). Sedation reduced the mean fish heart rate from 149 +/- 18 to 90 +/- 17 beats/min. The PR and QRS intervals remained unchanged in response to ventricular apical amputation (n = 6, p > 0.05). Corrected QT intervals (QTc) were shortened 4 dpa (n = 6, p < 0.05). In a parallel study, histology revealed that apical thrombi were replaced with fibrin clots and collagen fibers. Atrial arrhythmia was noted in response to prolonged sedation. Unlike the human counterpart, ventricular tachycardia or fibrillation was not observed in response to ventricular amputation 2 and 4 dpa. Taken together, we demonstrated a minimally invasive methodology to monitor zebrafish heart function, electrical activities, and regeneration in real-time.

The effects of cocaine on heart rate and electrocardiogram in zebrafish (Danio rerio)

“…In the present study we measured the effect of cocaine on these intervals in zebrafish. The interval lengths measured are similar to those reported in other studies on adults (Chaudhari et al, 2013; Milan et al, 2006; Sun et al, 2009). An interesting difference between our recordings and that reported by others is the sharp hyperpolarization after the P-wave.…”

“…The consensus in other studies recording ECGs in zebrafish sedated with tricaine suggest that the drug lengthens the ECG intervals, including QTc (Huang et al, 2010; Sun et al, 2009). Tricaine, like cocaine, blocks voltage-gated ion channels (Frazier and Narahashi, 1975).…”

“…ECG were performed essentially as described by others (Chaudhari et al, 2013; Milan et al, 2006; Sun et al, 2009). Zebrafish were sedated in tricaine as described by others (Westerfield, 2007), but with some differences in drug preparation.…”

Identifying Significant Biological Markers in Klotho Gene Variants Across Wide Ranging Taxonomy

“…Heterocephalus glaber are highly resistant to cancer, and can maintain a youthful vascular function and cellular oxidant-antioxidant phenotype relatively longer and are better protected against aging-induced oxidative stress than shorter-living rodents (Buffenstein, 2009;Csiszar et al, 2007;Pérez et al, 2009). Danio rerio have shown the ability to regenerate their fins, skin, and heart (Jopling, 2010;Sun et al, 2009 . In this operation, Hirschberg algorithm was selected for optimal matching.…”

Optical assessment of the cardiac rhythm of contracting cardiomyocytes in vitro and a pulsating heart in vivo for pharmacological screening

“…Through simultaneous recording of the atrial (P wave) and ventricular (QRS complex) electrical activities, details of the electrical conduction through the atrio-ventricular node (such as conductivity, conduction velocity et cetera) are revealed, based on which the pathophysiology of heart diseases or the outcome of therapeutic interventions can be assessed. ECG has been applied to zebrafish [14][15][16], but it is invasive because of a necessity to insert needle electrodes into the body of fish and demands skillful operation especially in small larvae [17,18]. Towards this end, various optical modalities have been developed to characterize the cardiac rhythm of zebrafish and other small animals such as goldfish and molluscs [11,19,20].…”