Cardiac response to startle stimuli in larval zebrafish: sympathetic and parasympathetic components

Abstract

Central regulation of cardiac output via the sympathetic and parasympathetic branches of the autonomic nervous system allows the organism to respond to environmental changes. Sudden onset stimuli, startle stimuli, are useful probes to study central regulatory responses to the environment. In mammals, startle stimuli induce a transient bradycardia that habituates with repeated stimulation. Repeated presentation of the stimulus results in tachycardia. In this study, we investigate the behavioral regulation of heart rate in response to sudden stimuli in the zebrafish. Larval zebrafish show a stereotyped heart rate response to mild electrical shock. Naïve fish show a significant increase in interbeat interval that resolves in the 2 s following stimulation. This transient bradycardia decreases on repeated exposure to the stimulus. Following repeated stimulation, the fish become tachycardic within 1 min of stimulation. Both the transient bradycardia and following tachycardia responses are blocked with administration of the ganglionic blocker hexamethonium, demonstrating that these responses are mediated centrally. The transient bradycardia is blocked by the muscarinic antagonist atropine, suggesting that this response is mediated by the parasympathetic system, while the following tachycardia is specifically blocked by the beta-adrenergic antagonist propranolol, suggesting that this response is mediated by the sympathetic nervous system. Together, these results demonstrate that at the larval stage, zebrafish actively regulate cardiac output to changes in their environment using both the parasympathetic and sympathetic branches of the autonomic nervous system, a behavioral response that is markedly similar to that observed in mammals to similar sudden onset stimuli. cardiac regulation; zebrafish AUTONOMIC DYSREGULATION APPEARS to play a key role in the development of cardiovascular disease (14), and genetic factors are hypothesized to contribute to the variable progression of the disease (30, 34). The startle response can be used as a probe for autonomic regulation of cardiac activity (4, 7). Both parasympathetic and sympathetic responses to the startle stimulus can be observed, which allows for both components of the autonomic nervous system to be probed with a single behavioral manipulation. This study seeks to establish the zebrafish larvae as a model organism to investigate autonomic regulation of cardiac activity by developing a rapid behavioral assay to probe for autonomic regulation and dysregulation of the cardiac output.In mammals, sudden onset stimuli induce a rapid change in behavior that consists of both locomotor activity and coincident autonomic behavioral changes. The locomotor activity, the startle response, may be characterized by a complex motor response involving contraction of the muscles of the eyelid, neck, and limbs [reviewed in (15)]. In rats, for example, an air-puff stimulus results in a stereotyped motor response and transient bradycardia (7). Repeated exposure to the stimulus results in decre...

Cynodon dactylon and Sida acuta extracts impact on the function of the cardiovascular system in zebrafish embryos

“…The methanolic extract of C. dactylon induced changes in the cardiac cycle (systole and diastole) and blood flow in the embryonic zebrafish at 3 dpf (74–80 hpf). Similarly, atropine induces an increase in HBR caused by the stimulation of cardiac cycle[26]. Small molecules from S. acuta decreased heart rate and similar effects were observed in propranolol, which also decreased heart rate in zebrafish embryo.…”

Kctd10 regulates heart morphogenesis by repressing the transcriptional activity of Tbx5a in zebrafish

“…Adrenaline, digilanid and atropine were provided by Peking University Hospital. The embryos of 24 hpf derived from the incross of kctd10 þ / À zebrafish were treated with adrenaline (250 mM), atropine (100 mM) and digilanid (10 mM), respectively [53][54][55] . After incubating at 28°C for 24 h, the larvae were anesthetized with MS-222 (ethyl-3-aminobenzoate methanesulfonate salt, Sigma-Aldrich Inc.) at 28°C.…”

“…After incubating at 28°C for 24 h, the larvae were anesthetized with MS-222 (ethyl-3-aminobenzoate methanesulfonate salt, Sigma-Aldrich Inc.) at 28°C. After 5 min, the images of the larvae were captured by a digital video camera attached to the microscope (Camtasia Studio) and the heart rate was calculated from the captured images 53,56 .…”

Pharmacological analyses of learning and memory in zebrafish (Danio rerio)

“…A tap-elicited startle reflex has been used in adolescent and adult zebrafish to characterize drug effects (e.g. Eddins et al, 2010), and touch- or auditory-elicited reflexes in larvae or young fish are also common (Liu et al, 2012; Mann et al, 2010). In the tap-elicited startle habituation, the stimulus is delivered at a standard interval (e.g.…”