M. Stoyek - Academia.edu (original) (raw)

Papers by M. Stoyek

Research paper thumbnail of From Mice to Mainframes: Experimental Models for Investigation of the Intracardiac Nervous System

Journal of Cardiovascular Development and Disease

The intracardiac nervous system (IcNS), sometimes referred to as the “little brain” of the heart,... more The intracardiac nervous system (IcNS), sometimes referred to as the “little brain” of the heart, is involved in modulating many aspects of cardiac physiology. In recent years our fundamental understanding of autonomic control of the heart has drastically improved, and the IcNS is increasingly being viewed as a therapeutic target in cardiovascular disease. However, investigations of the physiology and specific roles of intracardiac neurons within the neural circuitry mediating cardiac control has been hampered by an incomplete knowledge of the anatomical organisation of the IcNS. A more thorough understanding of the IcNS is hoped to promote the development of new, highly targeted therapies to modulate IcNS activity in cardiovascular disease. In this paper, we first provide an overview of IcNS anatomy and function derived from experiments in mammals. We then provide descriptions of alternate experimental models for investigation of the IcNS, focusing on a non-mammalian model (zebrafi...

Research paper thumbnail of B-PO02-021 Increased Microtubule Detyrosination Enhances Mechano-Arrhythmogenicity Through TRPA1 in Ventricular Myocytes

Research paper thumbnail of TRPA1 channels are a source of calcium-driven cardiac mechano-arrhythmogenicity

SUMMARY PARAGRAPHPhysiological systems require feedback to maintain normal function. In the heart... more SUMMARY PARAGRAPHPhysiological systems require feedback to maintain normal function. In the heart, electrical excitation causes mechanical contraction1, with feedback of mechanics to electrics occurring through ‘mechano-electric coupling’ processes2. In diseases that affect cardiac mechanics, this feedback can result in deadly mechanically-induced arrythmias (‘mechano-arrhythmogenicity’)3. However, the molecular identity of the specific factor(s) driving mechano-arrhythmogenicity are unknown4. Here we show that mechano-sensitive5–10 transient receptor potential kinase ankyrin 1 (TRPA1) channels11 are a source of cardiac mechano-arrhythmogenicity through a calcium (Ca2+)-driven mechanism. Using a cell-level approach involving stretch of single ventricular myocytes combined with simultaneous voltage-Ca2+ imaging, we found that activation of TRPA1 channels resulted in an increase in diastolic Ca2+ load and the appearance of stretch-induced arrhythmias, which were driven by trans-sarcol...

Research paper thumbnail of The identification of dual protective agents against cisplatin-induced oto-and nephrotoxicity using the zebrafish model

eLife

Dose-limiting toxicities for cisplatin administration, including ototoxicity and nephrotoxicity, ... more Dose-limiting toxicities for cisplatin administration, including ototoxicity and nephrotoxicity, impact the clinical utility of this effective chemotherapy agent and lead to lifelong complications, particularly in pediatric cancer survivors. Using a two-pronged drug screen employing the zebrafish lateral line as an in vivo readout for ototoxicity and kidney cell-based nephrotoxicity assay, we screened 1280 compounds and identified 22 that were both oto- and nephroprotective. Of these, dopamine and L-mimosine, a plant-based amino acid active in the dopamine pathway, were further investigated. Dopamine and L-mimosine protected the hair cells in the zebrafish otic vesicle from cisplatin-induced damage and preserved zebrafish larval glomerular filtration. Importantly, these compounds did not abrogate the cytotoxic effects of cisplatin on human cancer cells. This study provides insights into the mechanisms underlying cisplatin-induced oto- and nephrotoxicity and compelling preclinical ev...

Research paper thumbnail of Cardiac Electrophysiological Effects of Light-Activated Chloride Channels

Frontiers in Physiology

During the last decade, optogenetics has emerged as a paradigm-shifting technique to monitor and ... more During the last decade, optogenetics has emerged as a paradigm-shifting technique to monitor and steer the behavior of specific cell types in excitable tissues, including the heart. Activation of cation-conducting channelrhodopsins (ChR) leads to membrane depolarization, allowing one to effectively trigger action potentials (AP) in cardiomyocytes. In contrast, the quest for optogenetic tools for hyperpolarization-induced inhibition of AP generation has remained challenging. The green-light activated ChR from Guillardia theta (GtACR1) mediates Cl −-driven photocurrents that have been shown to silence AP generation in different types of neurons. It has been suggested, therefore, to be a suitable tool for inhibition of cardiomyocyte activity. Using single-cell electrophysiological recordings and contraction tracking, as well as intracellular microelectrode recordings and in vivo optical recordings of whole hearts, we find that GtACR1 activation by prolonged illumination arrests cardiac cells in a depolarized state, thus inhibiting re-excitation. In line with this, GtACR1 activation by transient light pulses elicits AP in rabbit isolated cardiomyocytes and in spontaneously beating intact hearts of zebrafish. Our results show that GtACR1 inhibition of AP generation is caused by cell depolarization. While this does not address the need for optogenetic silencing through physiological means (i.e., hyperpolarization), GtACR1 is a potentially attractive tool for activating cardiomyocytes by transient light-induced depolarization.

Research paper thumbnail of Age-associated changes in electrical function of the zebrafish heart

Progress in Biophysics and Molecular Biology

Research paper thumbnail of One fish, two fish, red fish, blue fish*: Zebrafish as a model for cardiac research

Progress in Biophysics and Molecular Biology

Research paper thumbnail of Single cell investigation of mechanically-induced arrhythmias during acute ischemia

Journal of Molecular and Cellular Cardiology

Research paper thumbnail of Etiology and functional validation of gastrointestinal motility dysfunction in a zebrafish model of CHARGE syndrome

The FEBS journal, Jan 16, 2018

CHARGE syndrome is linked to autosomal dominant mutations in the CHD7 gene and results in a numbe... more CHARGE syndrome is linked to autosomal dominant mutations in the CHD7 gene and results in a number of physiological and structural abnormalities, including heart defects, hearing and vision loss and gastrointestinal (GI) problems. Of these challenges, GI problems have a profound impact throughout an individual's life, resulting in increased morbidity and mortality. A homologue of CHD7 has been identified in the zebrafish, the loss of which recapitulates many of the features of the human disease. Using a morpholino chd7 knockdown model complemented by a chd7 null mutant zebrafish line, we examined GI structure, innervation, and motility in larval zebrafish. Loss of chd7 resulted in physically smaller GI tracts with normal epithelial and muscular histology, but decreased and disorganized vagal projections, particularly in the foregut. chd7 morphant larvae had significantly less ability to empty their GI tract of gavaged fluorescent beads, and this condition was only minimally impr...

Research paper thumbnail of Skeletal stiffening in an amphibious fish out of water is a response to increased body weight

The Journal of experimental biology, Oct 15, 2017

Terrestrial animals must support their bodies against gravity, while aquatic animals are effectiv... more Terrestrial animals must support their bodies against gravity, while aquatic animals are effectively weightless because of buoyant support from water. Given this evolutionary history of minimal gravitational loading of fishes in water, it has been hypothesized that weight-responsive musculoskeletal systems evolved during the tetrapod invasion of land and are thus absent in fishes. Amphibious fishes, however, experience increased effective weight when out of water - are these fishes responsive to gravitational loading? Contrary to the tetrapod-origin hypothesis, we found that terrestrial acclimation reversibly increased gill arch stiffness (∼60% increase) in the amphibious fish Kryptolebias marmoratus when loaded normally by gravity, but not under simulated microgravity. Quantitative proteomics analysis revealed that this change in mechanical properties occurred via increased abundance of proteins responsible for bone mineralization in other fishes as well as in tetrapods. Type X col...

Research paper thumbnail of hace1 Influences zebrafish cardiac development via ROS-dependent mechanisms

Developmental dynamics : an official publication of the American Association of Anatomists, Feb 11, 2017

In this study, we reveal a previously undescribed role of the HACE1 (HECT domain and Ankyrin repe... more In this study, we reveal a previously undescribed role of the HACE1 (HECT domain and Ankyrin repeat Containing E3 ubiquitin-protein ligase 1) tumor suppressor protein in normal vertebrate heart development using the zebrafish (Danio rerio) model. We examined the link between the cardiac phenotypes associated with hace1 loss of function to the expression of the Rho small family GTPase, rac1, which is a known target of HACE1 and promotes ROS production via its interaction with NADPH oxidase holoenzymes. We demonstrate that loss of hace1 in zebrafish via morpholino knockdown results in cardiac deformities, specifically a looping defect, where the heart is either tubular or "inverted". Whole-mount in situ hybridization of cardiac markers shows distinct abnormalities in ventricular morphology and atrioventricular valve formation in the hearts of these morphants, as well as increased expression of rac1. Importantly, this phenotype appears to be directly related to Nox enzyme-dep...

Research paper thumbnail of Distribution and chronotropic effects of serotonin in the zebrafish heart

Autonomic Neuroscience

Several lines of evidence suggest that serotonin (5-HT) has a regulatory role in cardiovascular f... more Several lines of evidence suggest that serotonin (5-HT) has a regulatory role in cardiovascular function from embryogenesis through adulthood. However, the reported actions of 5-HT are often contradictory and include bradycardia or tachycardia, hypotension or hypertension, and vasodilation or vasoconstriction. Clarifying such cardiac effects requires further research and may benefit from utilizing a model simpler than the mammalian hearts traditionally used in these studies. In the present study, we describe the cardiac distribution and chronotropic responses of 5-HT in the zebrafish heart. A combined anatomical, electrophysiological, and pharmacological approach was used to investigate the involvement of 5-HT pathways, and to compare neural and direct myocardial pathways of biological action. Immunohistochemical methods revealed 5-HT in endocardial cells, glial-like cells, and intracardiac neurons in the atrium. Electrocardiogram (ECG) recordings combined with the administration of pharmacological agents demonstrated that 5-HT acted predominantly through direct myocardial pathways resulting in a reduction of heart rate. Overall, the results of this study contribute significant advances in the establishment of the zebrafish as a new model for studies of the role of 5-HT in autonomic cardiac control.

Research paper thumbnail of The in vitro zebrafish heart as a model to investigate the chronotropic effects of vapor anesthetics

American journal of physiology. Regulatory, integrative and comparative physiology, Jan 6, 2017

In addition to their intended clinical actions, all general anesthetic agents in common use have ... more In addition to their intended clinical actions, all general anesthetic agents in common use have detrimental intra- and post-surgical side effects on organs and systems including the heart. The major cardiac side effect of anesthesia is bradycardia, which increases the probability of insufficient systemic perfusion during surgery. These side effects also occur in all vertebrate species so far examined, but the underlying mechanisms are not clear. The zebrafish heart is a powerful model for studying cardiac electrophysiology, employing the same pacemaker system and neural control as do mammalian hearts. In this study isolated zebrafish hearts were significantly bradycardic during exposure to the vapor anesthetics sevoflurane (SEVO), desflurane (DES) and isoflurane (ISO). Bradycardia induced by DES and ISO continued during pharmacological blockade of the intracardiac portion of the autonomic nervous system, but the chronotropic effect of SEVO was eliminated during blockade. Bradycardi...

Research paper thumbnail of Intrinsic regulation of sinoatrial node function and the zebrafish as a model of stretch effects on pacemaking

Progress in biophysics and molecular biology, Jan 22, 2017

Excitation of the heart occurs in a specialised region known as the sinoatrial node (SAN). Tight ... more Excitation of the heart occurs in a specialised region known as the sinoatrial node (SAN). Tight regulation of SAN function is essential for the maintenance of normal heart rhythm and the response to (patho-)physiological changes. The SAN is regulated by extrinsic (central nervous system) and intrinsic (neurons, peptides, mechanics) factors. The positive chronotropic response to stretch in particular is essential for beat-by-beat adaptation to changes in hemodynamic load. Yet, the mechanism of this stretch response is unknown, due in part to the lack of an appropriate experimental model for targeted investigations. We have been investigating the zebrafish as a model for the study of intrinsic regulation of SAN function. In this paper, we first briefly review current knowledge of the principal components of extrinsic and intrinsic SAN regulation, derived primarily from experiments in mammals, followed by a description of the zebrafish as a novel experimental model for studies of intr...

Research paper thumbnail of Data on horizontal and vertical movements of zebrafish during appetitive conditioning

Data in brief, 2016

This article provides supporting data for the research article "A simple automated system fo... more This article provides supporting data for the research article "A simple automated system for appetitive conditioning of zebrafish in their home tanks" (J.M. Doyle, N. Merovitch, R.C. Wyeth, M.R. Stoyek, M. Schmidt, F. Wilfart, A. Fine, R.P. Croll, 2016) [1]. In that article, we described overall movements of zebrafish toward a food source as a response to auditory or visual cues as conditioned stimuli in a novel learning paradigm. Here, we describe separate analyses of the vertical and horizontal components of the learned response. These data provide evidence that the conditioning might result from both classical conditioning of an innate response of zebrafish to move to the surface in response to food cues and secondary conditioning of the fish to associate a food presentation with a specific location in the tank. Movement data from the twenty trial acquisition period and probe trials from 2-32 days post conditioning are included.

Research paper thumbnail of A simple automated system for appetitive conditioning of zebrafish in their home tanks

Behavioural brain research, Jan 19, 2016

We describe here an automated apparatus that permits rapid conditioning paradigms for zebrafish. ... more We describe here an automated apparatus that permits rapid conditioning paradigms for zebrafish. Arduino microprocessors were used to control the delivery of auditory or visual stimuli to groups of adult or juvenile zebrafish in their home tanks in a conventional zebrafish facility. An automatic feeder dispensed precise amounts of food immediately after the conditioned stimuli, or at variable delays for controls. Responses were recorded using inexpensive cameras, with the video sequences analysed with ImageJ or Matlab. Fish showed significant conditioned responses in as few as 5 trials, learning that the conditioned stimulus was a predictor of food presentation at the water surface and at the end of the tank where the food was dispensed. Memories of these conditioned associations persisted for at least 2days after training when fish were tested either as groups or as individuals. Control fish, for which the auditory or visual stimuli were specifically unpaired with food, showed no c...

Research paper thumbnail of Effects of wall compliance on swimbladder function in zebrafish

Research paper thumbnail of The isolated zebrafish heart as a model to investigate the basic mechanisms of cardiac side effects of modern anesthetics

Research paper thumbnail of Effects of different modalities of simulated microgravity on embryonic development of zebrafish, Danio rerio

Research paper thumbnail of Zebrafish heart as a model to study the integrative autonomic control of pacemaker function

American Journal of Physiology - Heart and Circulatory Physiology

The cardiac pacemaker sets the heart's primary rate, with pacemaker discharge controlled by t... more The cardiac pacemaker sets the heart's primary rate, with pacemaker discharge controlled by the autonomic nervous system through intracardiac ganglia. A fundamental issue in understanding the relationship between neural activity and cardiac chronotropy is the identification of neuronal populations that control pacemaker cells. To date, most studies of neurocardiac control have been done in mammalian species, where neurons are embedded in and distributed throughout the heart, so they are largely inaccessible for whole-organ, integrative studies. Here, we establish the isolated, innervated zebrafish heart as a novel alternative model for studies of autonomic control of heart rate. Stimulation of individual cardiac vagosympathetic nerve trunks evoked bradycardia (parasympathetic activation) and tachycardia (sympathetic activation). Simultaneous stimulation of both vagosympathetic nerve trunks evoked a summative effect. Effects of nerve stimulation were mimicked by direct applicatio...

Research paper thumbnail of From Mice to Mainframes: Experimental Models for Investigation of the Intracardiac Nervous System

Journal of Cardiovascular Development and Disease

The intracardiac nervous system (IcNS), sometimes referred to as the “little brain” of the heart,... more The intracardiac nervous system (IcNS), sometimes referred to as the “little brain” of the heart, is involved in modulating many aspects of cardiac physiology. In recent years our fundamental understanding of autonomic control of the heart has drastically improved, and the IcNS is increasingly being viewed as a therapeutic target in cardiovascular disease. However, investigations of the physiology and specific roles of intracardiac neurons within the neural circuitry mediating cardiac control has been hampered by an incomplete knowledge of the anatomical organisation of the IcNS. A more thorough understanding of the IcNS is hoped to promote the development of new, highly targeted therapies to modulate IcNS activity in cardiovascular disease. In this paper, we first provide an overview of IcNS anatomy and function derived from experiments in mammals. We then provide descriptions of alternate experimental models for investigation of the IcNS, focusing on a non-mammalian model (zebrafi...

Research paper thumbnail of B-PO02-021 Increased Microtubule Detyrosination Enhances Mechano-Arrhythmogenicity Through TRPA1 in Ventricular Myocytes

Research paper thumbnail of TRPA1 channels are a source of calcium-driven cardiac mechano-arrhythmogenicity

SUMMARY PARAGRAPHPhysiological systems require feedback to maintain normal function. In the heart... more SUMMARY PARAGRAPHPhysiological systems require feedback to maintain normal function. In the heart, electrical excitation causes mechanical contraction1, with feedback of mechanics to electrics occurring through ‘mechano-electric coupling’ processes2. In diseases that affect cardiac mechanics, this feedback can result in deadly mechanically-induced arrythmias (‘mechano-arrhythmogenicity’)3. However, the molecular identity of the specific factor(s) driving mechano-arrhythmogenicity are unknown4. Here we show that mechano-sensitive5–10 transient receptor potential kinase ankyrin 1 (TRPA1) channels11 are a source of cardiac mechano-arrhythmogenicity through a calcium (Ca2+)-driven mechanism. Using a cell-level approach involving stretch of single ventricular myocytes combined with simultaneous voltage-Ca2+ imaging, we found that activation of TRPA1 channels resulted in an increase in diastolic Ca2+ load and the appearance of stretch-induced arrhythmias, which were driven by trans-sarcol...

Research paper thumbnail of The identification of dual protective agents against cisplatin-induced oto-and nephrotoxicity using the zebrafish model

eLife

Dose-limiting toxicities for cisplatin administration, including ototoxicity and nephrotoxicity, ... more Dose-limiting toxicities for cisplatin administration, including ototoxicity and nephrotoxicity, impact the clinical utility of this effective chemotherapy agent and lead to lifelong complications, particularly in pediatric cancer survivors. Using a two-pronged drug screen employing the zebrafish lateral line as an in vivo readout for ototoxicity and kidney cell-based nephrotoxicity assay, we screened 1280 compounds and identified 22 that were both oto- and nephroprotective. Of these, dopamine and L-mimosine, a plant-based amino acid active in the dopamine pathway, were further investigated. Dopamine and L-mimosine protected the hair cells in the zebrafish otic vesicle from cisplatin-induced damage and preserved zebrafish larval glomerular filtration. Importantly, these compounds did not abrogate the cytotoxic effects of cisplatin on human cancer cells. This study provides insights into the mechanisms underlying cisplatin-induced oto- and nephrotoxicity and compelling preclinical ev...

Research paper thumbnail of Cardiac Electrophysiological Effects of Light-Activated Chloride Channels

Frontiers in Physiology

During the last decade, optogenetics has emerged as a paradigm-shifting technique to monitor and ... more During the last decade, optogenetics has emerged as a paradigm-shifting technique to monitor and steer the behavior of specific cell types in excitable tissues, including the heart. Activation of cation-conducting channelrhodopsins (ChR) leads to membrane depolarization, allowing one to effectively trigger action potentials (AP) in cardiomyocytes. In contrast, the quest for optogenetic tools for hyperpolarization-induced inhibition of AP generation has remained challenging. The green-light activated ChR from Guillardia theta (GtACR1) mediates Cl −-driven photocurrents that have been shown to silence AP generation in different types of neurons. It has been suggested, therefore, to be a suitable tool for inhibition of cardiomyocyte activity. Using single-cell electrophysiological recordings and contraction tracking, as well as intracellular microelectrode recordings and in vivo optical recordings of whole hearts, we find that GtACR1 activation by prolonged illumination arrests cardiac cells in a depolarized state, thus inhibiting re-excitation. In line with this, GtACR1 activation by transient light pulses elicits AP in rabbit isolated cardiomyocytes and in spontaneously beating intact hearts of zebrafish. Our results show that GtACR1 inhibition of AP generation is caused by cell depolarization. While this does not address the need for optogenetic silencing through physiological means (i.e., hyperpolarization), GtACR1 is a potentially attractive tool for activating cardiomyocytes by transient light-induced depolarization.

Research paper thumbnail of Age-associated changes in electrical function of the zebrafish heart

Progress in Biophysics and Molecular Biology

Research paper thumbnail of One fish, two fish, red fish, blue fish*: Zebrafish as a model for cardiac research

Progress in Biophysics and Molecular Biology

Research paper thumbnail of Single cell investigation of mechanically-induced arrhythmias during acute ischemia

Journal of Molecular and Cellular Cardiology

Research paper thumbnail of Etiology and functional validation of gastrointestinal motility dysfunction in a zebrafish model of CHARGE syndrome

The FEBS journal, Jan 16, 2018

CHARGE syndrome is linked to autosomal dominant mutations in the CHD7 gene and results in a numbe... more CHARGE syndrome is linked to autosomal dominant mutations in the CHD7 gene and results in a number of physiological and structural abnormalities, including heart defects, hearing and vision loss and gastrointestinal (GI) problems. Of these challenges, GI problems have a profound impact throughout an individual's life, resulting in increased morbidity and mortality. A homologue of CHD7 has been identified in the zebrafish, the loss of which recapitulates many of the features of the human disease. Using a morpholino chd7 knockdown model complemented by a chd7 null mutant zebrafish line, we examined GI structure, innervation, and motility in larval zebrafish. Loss of chd7 resulted in physically smaller GI tracts with normal epithelial and muscular histology, but decreased and disorganized vagal projections, particularly in the foregut. chd7 morphant larvae had significantly less ability to empty their GI tract of gavaged fluorescent beads, and this condition was only minimally impr...

Research paper thumbnail of Skeletal stiffening in an amphibious fish out of water is a response to increased body weight

The Journal of experimental biology, Oct 15, 2017

Terrestrial animals must support their bodies against gravity, while aquatic animals are effectiv... more Terrestrial animals must support their bodies against gravity, while aquatic animals are effectively weightless because of buoyant support from water. Given this evolutionary history of minimal gravitational loading of fishes in water, it has been hypothesized that weight-responsive musculoskeletal systems evolved during the tetrapod invasion of land and are thus absent in fishes. Amphibious fishes, however, experience increased effective weight when out of water - are these fishes responsive to gravitational loading? Contrary to the tetrapod-origin hypothesis, we found that terrestrial acclimation reversibly increased gill arch stiffness (∼60% increase) in the amphibious fish Kryptolebias marmoratus when loaded normally by gravity, but not under simulated microgravity. Quantitative proteomics analysis revealed that this change in mechanical properties occurred via increased abundance of proteins responsible for bone mineralization in other fishes as well as in tetrapods. Type X col...

Research paper thumbnail of hace1 Influences zebrafish cardiac development via ROS-dependent mechanisms

Developmental dynamics : an official publication of the American Association of Anatomists, Feb 11, 2017

In this study, we reveal a previously undescribed role of the HACE1 (HECT domain and Ankyrin repe... more In this study, we reveal a previously undescribed role of the HACE1 (HECT domain and Ankyrin repeat Containing E3 ubiquitin-protein ligase 1) tumor suppressor protein in normal vertebrate heart development using the zebrafish (Danio rerio) model. We examined the link between the cardiac phenotypes associated with hace1 loss of function to the expression of the Rho small family GTPase, rac1, which is a known target of HACE1 and promotes ROS production via its interaction with NADPH oxidase holoenzymes. We demonstrate that loss of hace1 in zebrafish via morpholino knockdown results in cardiac deformities, specifically a looping defect, where the heart is either tubular or "inverted". Whole-mount in situ hybridization of cardiac markers shows distinct abnormalities in ventricular morphology and atrioventricular valve formation in the hearts of these morphants, as well as increased expression of rac1. Importantly, this phenotype appears to be directly related to Nox enzyme-dep...

Research paper thumbnail of Distribution and chronotropic effects of serotonin in the zebrafish heart

Autonomic Neuroscience

Several lines of evidence suggest that serotonin (5-HT) has a regulatory role in cardiovascular f... more Several lines of evidence suggest that serotonin (5-HT) has a regulatory role in cardiovascular function from embryogenesis through adulthood. However, the reported actions of 5-HT are often contradictory and include bradycardia or tachycardia, hypotension or hypertension, and vasodilation or vasoconstriction. Clarifying such cardiac effects requires further research and may benefit from utilizing a model simpler than the mammalian hearts traditionally used in these studies. In the present study, we describe the cardiac distribution and chronotropic responses of 5-HT in the zebrafish heart. A combined anatomical, electrophysiological, and pharmacological approach was used to investigate the involvement of 5-HT pathways, and to compare neural and direct myocardial pathways of biological action. Immunohistochemical methods revealed 5-HT in endocardial cells, glial-like cells, and intracardiac neurons in the atrium. Electrocardiogram (ECG) recordings combined with the administration of pharmacological agents demonstrated that 5-HT acted predominantly through direct myocardial pathways resulting in a reduction of heart rate. Overall, the results of this study contribute significant advances in the establishment of the zebrafish as a new model for studies of the role of 5-HT in autonomic cardiac control.

Research paper thumbnail of The in vitro zebrafish heart as a model to investigate the chronotropic effects of vapor anesthetics

American journal of physiology. Regulatory, integrative and comparative physiology, Jan 6, 2017

In addition to their intended clinical actions, all general anesthetic agents in common use have ... more In addition to their intended clinical actions, all general anesthetic agents in common use have detrimental intra- and post-surgical side effects on organs and systems including the heart. The major cardiac side effect of anesthesia is bradycardia, which increases the probability of insufficient systemic perfusion during surgery. These side effects also occur in all vertebrate species so far examined, but the underlying mechanisms are not clear. The zebrafish heart is a powerful model for studying cardiac electrophysiology, employing the same pacemaker system and neural control as do mammalian hearts. In this study isolated zebrafish hearts were significantly bradycardic during exposure to the vapor anesthetics sevoflurane (SEVO), desflurane (DES) and isoflurane (ISO). Bradycardia induced by DES and ISO continued during pharmacological blockade of the intracardiac portion of the autonomic nervous system, but the chronotropic effect of SEVO was eliminated during blockade. Bradycardi...

Research paper thumbnail of Intrinsic regulation of sinoatrial node function and the zebrafish as a model of stretch effects on pacemaking

Progress in biophysics and molecular biology, Jan 22, 2017

Excitation of the heart occurs in a specialised region known as the sinoatrial node (SAN). Tight ... more Excitation of the heart occurs in a specialised region known as the sinoatrial node (SAN). Tight regulation of SAN function is essential for the maintenance of normal heart rhythm and the response to (patho-)physiological changes. The SAN is regulated by extrinsic (central nervous system) and intrinsic (neurons, peptides, mechanics) factors. The positive chronotropic response to stretch in particular is essential for beat-by-beat adaptation to changes in hemodynamic load. Yet, the mechanism of this stretch response is unknown, due in part to the lack of an appropriate experimental model for targeted investigations. We have been investigating the zebrafish as a model for the study of intrinsic regulation of SAN function. In this paper, we first briefly review current knowledge of the principal components of extrinsic and intrinsic SAN regulation, derived primarily from experiments in mammals, followed by a description of the zebrafish as a novel experimental model for studies of intr...

Research paper thumbnail of Data on horizontal and vertical movements of zebrafish during appetitive conditioning

Data in brief, 2016

This article provides supporting data for the research article "A simple automated system fo... more This article provides supporting data for the research article "A simple automated system for appetitive conditioning of zebrafish in their home tanks" (J.M. Doyle, N. Merovitch, R.C. Wyeth, M.R. Stoyek, M. Schmidt, F. Wilfart, A. Fine, R.P. Croll, 2016) [1]. In that article, we described overall movements of zebrafish toward a food source as a response to auditory or visual cues as conditioned stimuli in a novel learning paradigm. Here, we describe separate analyses of the vertical and horizontal components of the learned response. These data provide evidence that the conditioning might result from both classical conditioning of an innate response of zebrafish to move to the surface in response to food cues and secondary conditioning of the fish to associate a food presentation with a specific location in the tank. Movement data from the twenty trial acquisition period and probe trials from 2-32 days post conditioning are included.

Research paper thumbnail of A simple automated system for appetitive conditioning of zebrafish in their home tanks

Behavioural brain research, Jan 19, 2016

We describe here an automated apparatus that permits rapid conditioning paradigms for zebrafish. ... more We describe here an automated apparatus that permits rapid conditioning paradigms for zebrafish. Arduino microprocessors were used to control the delivery of auditory or visual stimuli to groups of adult or juvenile zebrafish in their home tanks in a conventional zebrafish facility. An automatic feeder dispensed precise amounts of food immediately after the conditioned stimuli, or at variable delays for controls. Responses were recorded using inexpensive cameras, with the video sequences analysed with ImageJ or Matlab. Fish showed significant conditioned responses in as few as 5 trials, learning that the conditioned stimulus was a predictor of food presentation at the water surface and at the end of the tank where the food was dispensed. Memories of these conditioned associations persisted for at least 2days after training when fish were tested either as groups or as individuals. Control fish, for which the auditory or visual stimuli were specifically unpaired with food, showed no c...

Research paper thumbnail of Effects of wall compliance on swimbladder function in zebrafish

Research paper thumbnail of The isolated zebrafish heart as a model to investigate the basic mechanisms of cardiac side effects of modern anesthetics

Research paper thumbnail of Effects of different modalities of simulated microgravity on embryonic development of zebrafish, Danio rerio

Research paper thumbnail of Zebrafish heart as a model to study the integrative autonomic control of pacemaker function

American Journal of Physiology - Heart and Circulatory Physiology

The cardiac pacemaker sets the heart's primary rate, with pacemaker discharge controlled by t... more The cardiac pacemaker sets the heart's primary rate, with pacemaker discharge controlled by the autonomic nervous system through intracardiac ganglia. A fundamental issue in understanding the relationship between neural activity and cardiac chronotropy is the identification of neuronal populations that control pacemaker cells. To date, most studies of neurocardiac control have been done in mammalian species, where neurons are embedded in and distributed throughout the heart, so they are largely inaccessible for whole-organ, integrative studies. Here, we establish the isolated, innervated zebrafish heart as a novel alternative model for studies of autonomic control of heart rate. Stimulation of individual cardiac vagosympathetic nerve trunks evoked bradycardia (parasympathetic activation) and tachycardia (sympathetic activation). Simultaneous stimulation of both vagosympathetic nerve trunks evoked a summative effect. Effects of nerve stimulation were mimicked by direct applicatio...