Abstract
The zebrafish (Danio rerio) has been used as a model for studying vertebrate development in the cardiovascular system. In order to monitor heart contraction and cytosolic calcium oscillations, fish were either embedded in methylcellulose or anesthetized with tricaine. Using high-resolution differential interference contrast and calcium imaging microscopy, we here show that dopamine and verapamil alter calcium signaling and muscle contraction in anesthetized zebrafish, but not in embedded zebrafish. In anesthetized fish, dopamine increases the amplitude of cytosolic calcium oscillation with a subsequent increase in heart contraction, whereas verapamil decreases the frequency of calcium oscillation and heart rate. Interestingly, verapamil also increases myocardial contraction. Our data further indicate that verapamil can increase myocardial calcium sensitivity in anesthetized fish. Taken together, our data reinforce in vivo cardiac responses to dopamine and verapamil. Furthermore, effects of dopamine and verapamil on myocardial calcium and contraction are greater in anesthetized than embedded fish. We suggest that while the zebrafish is an excellent model for a cardiovascular imaging study, the cardio-pharmacological profiles are very different between anesthetized and embedded fish.
Highlights
The zebrafish (Danio rerio) has become an important model organism for studying various diseases, genetic variations, protein functions, behavioral selectivity, environmental toxicology, and many other physiological responses for high-throughput chemical screening (Carvan et al, 2004; Burns et al, 2005; Wessely and Obara, 2008; Ingham, 2009)
We are the first to examine the effects of pharmacological agents on both cardiac cytosolic calcium and myocardial contraction simultaneously in vivo in nontransgenic 1-week-old zebrafish (Figure 1)
We demonstrate that pharmacological agents, such as verapamil, have the potential to change myocardial calcium sensitivity in anesthetized fish
Summary
The zebrafish (Danio rerio) has become an important model organism for studying various diseases, genetic variations, protein functions, behavioral selectivity, environmental toxicology, and many other physiological responses for high-throughput chemical screening (Carvan et al, 2004; Burns et al, 2005; Wessely and Obara, 2008; Ingham, 2009). In many other animal models, in vivo physiological imaging of internal organs has remained relatively inaccessible. Calcium imaging using probes has been used in zebrafish in vivo (Huisken et al, 2004; Ebert et al, 2005; Milan et al, 2006; Arnaout et al, 2007; Chi et al, 2008) and confirmed in the isolated heart (Sehnert et al, 2002; Sedmera et al, 2003; Langenbacher et al, 2005). The patterns of free calcium have been measured in zebrafish embryos (Creton et al, 1998)
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