Loss of M2 muscarinic receptor function inhibits development of hypoxic bradycardia and alters cardiac β-adrenergic sensitivity in larval zebrafish (Danio rerio)

2009 ◽  
Vol 297 (2) ◽  
pp. R412-R420 ◽  
Author(s):  
Shelby L. Steele ◽  
Kwok Hong Andy Lo ◽  
Vincent Wai Tsun Li ◽  
Shuk Han Cheng ◽  
Marc Ekker ◽  
...  
Keyword(s):  
Heart Rate ◽  
Muscarinic Receptor ◽  
Danio Rerio ◽  
Antisense Oligonucleotides ◽  
Adrenergic Receptor ◽  
Larval Zebrafish ◽  
M2 Muscarinic Receptor ◽  
Β Adrenergic Receptors ◽  
Relative Mrna Expression

Fish exposed to hypoxia develop decreased heart rate, or bradycardia, the physiological significance of which remains unknown. The general muscarinic receptor antagonist atropine abolishes the development of this hypoxic bradycardia, suggesting the involvement of muscarinic receptors. In this study, we tested the hypothesis that the hypoxic bradycardia is mediated specifically by stimulation of the M2 muscarinic receptor, the most abundant subtype in the vertebrate heart. Zebrafish ( Danio rerio) were reared at two levels of hypoxia (30 and 40 Torr Po2) from the point of fertilization. In hypoxic fish, the heart rate was significantly lower than in normoxic controls from 2 to 10 days postfertilization (dpf). At the more severe level of hypoxia (30 Torr Po2), there were significant increases in the relative mRNA expression of M 2 and the cardiac type β-adrenergic receptors ( β1AR, β2aAR, and β2bAR) at 4 dpf. The hypoxic bradycardia was abolished (at 40 Torr Po2) or significantly attenuated (at 30 Torr Po2) in larvae experiencing M2 receptor knockdown (using morpholino antisense oligonucleotides). Sham-injected larvae exhibited typical hypoxic bradycardia in both hypoxic regimens. The expression of β1AR, β2aAR, β2bAR, and M 2 mRNA was altered at various stages between 1 and 4 dpf in larvae experiencing M2 receptor knockdown. Interestingly, M2 receptor knockdown revealed a cardioinhibitory role for the β2-adrenergic receptor. This is the first study to demonstrate a specific role of the M2 muscarinic receptor in the initiation of hypoxic bradycardia in fish.

β-Adrenergic regulation of Na+ uptake by larval zebrafish Danio rerio in acidic and ion-poor environments

2012 ◽  
Vol 303 (10) ◽  
pp. R1031-R1041 ◽  
Author(s):  
Yusuke Kumai ◽  
Mellissa A. R. Ward ◽  
Steve F. Perry
Keyword(s):  
Danio Rerio ◽  
Adrenergic Receptors ◽  
Adrenergic Receptor ◽  
Receptor Agonist ◽  
Acidic Water ◽  
Adrenergic Systems ◽  
Β Receptor ◽  
Β Adrenergic Receptors ◽  
Adrenergic Receptor Agonist

The potential role of adrenergic systems in regulating Na+ uptake in zebrafish ( Danio rerio) larvae was investigated. Treatment with isoproterenol (a generic β-adrenergic receptor agonist) stimulated Na+ uptake, whereas treatment with phenylephrine (an α1-adrenergic receptor agonist) as well as clonidine (an α2-adrenergic receptor agonist) significantly reduced Na+ uptake, suggesting opposing roles of α- and β-adrenergic receptors in Na+ uptake regulation. The increase in Na+ uptake associated with exposure to acidic water (pH = 4.0) was attenuated in the presence of the nonselective β-receptor antagonist propranolol or the β1-receptor blocker atenolol; the β2-receptor antagonist ICI-118551 was without effect. The stimulation of Na+ uptake associated with ion-poor water (32-fold dilution of Ottawa tapwater) was unaffected by β-receptor blockade. Translational gene knockdown of β-receptors using antisense oligonucleotide morpholinos was used as a second method to assess the role of adrenergic systems in the regulation of Na+ uptake. Whereas β1- or β2B-receptor knockdown led to significant decreases in Na+ uptake during exposure to acidic water, only β2A-receptor morphants failed to increase Na+ uptake in response to ion-poor water. In support of the pharmacology and knockdown experiments that demonstrated an involvement of β-adrenergic systems in the control of Na+ uptake, we showed that the H+-ATPase-rich (HR) cell, a subtype of ionocyte known to be a site of Na+ uptake, is innervated and appears to express β-adrenergic receptors (propranolol binding sites) at 4 days postfertilization. These data indicate an important role of adrenergic systems in regulating Na+ uptake in developing zebrafish.

scholarly journals The role of TASK-2 channels in CO2 sensing in zebrafish (Danio rerio)

2020 ◽  
Vol 319 (3) ◽  
pp. R329-R342
Author(s):  
N. Koudrina ◽  
S. F. Perry ◽  
K. M. Gilmour
Keyword(s):  
Danio Rerio ◽  
Ventilatory Response ◽  
Indirect Evidence ◽  
Adult Zebrafish ◽  
Larval Zebrafish ◽  
Neuroepithelial Cells ◽  
Cardiorespiratory Reflexes ◽  
Or Task ◽  
And Task

Peripheral chemosensitivity in fishes is thought to be mediated by serotonin-enriched neuroepithelial cells (NECs) that are localized to the gills of adults and the integument of larvae. In adult zebrafish ( Danio rerio), branchial NECs are presumed to mediate the cardiorespiratory reflexes associated with hypoxia or hypercapnia, whereas in larvae, there is indirect evidence linking cutaneous NECs to hypoxic hyperventilation and hypercapnic tachycardia. No study yet has examined the ventilatory response of larval zebrafish to hypercapnia, and regardless of developmental stage, the signaling pathways involved in CO2 sensing remain unclear. In the mouse, a background potassium channel (TASK-2) contributes to the sensitivity of chemoreceptor cells to CO2. Zebrafish possess two TASK-2 channel paralogs, TASK-2 and TASK-2b, encoded by kcnk5a and kcnk5b, respectively. The present study aimed to determine whether TASK-2 channels are expressed in NECs of larval zebrafish and whether they are involved in CO2 sensing. Using immunohistochemical approaches, TASK-2 protein was observed on the surface of NECs in larvae. Exposure of larvae to hypercapnia caused cardiac and breathing frequencies to increase, and these responses were blunted in fish experiencing TASK-2 and/or TASK-2b knockdown. The results of these experiments suggest that TASK-2 channels are involved in CO2 sensing by NECs and contribute to the initiation of reflex cardiorespiratory responses during exposure of larvae to hypercapnia.

scholarly journals Role of K+ Channels in M2 Muscarinic Receptor-Mediated Inhibition of Noradrenaline Release From the Rat Stomach

2004 ◽  
Vol 96 (3) ◽  
pp. 286-292 ◽  
Author(s):  
Kumiko Nakamura ◽  
Shoshiro Okada ◽  
Naoko Yamaguchi ◽  
Takahiro Shimizu ◽  
Keiko Yokotani ◽  
...  
Keyword(s):  
Muscarinic Receptor ◽  
Noradrenaline Release ◽  
Rat Stomach ◽  
K Channels ◽  
M2 Muscarinic Receptor

Effect of targeted deletions of β1- and β2-adrenergic-receptor subtypes on heart rate variability

2006 ◽  
Vol 290 (1) ◽  
pp. H192-H199 ◽  
Author(s):  
Phillip M. Ecker ◽  
Chu-Chuan Lin ◽  
Jennifer Powers ◽  
Brian K. Kobilka ◽  
Anne M. Dubin ◽  
...  
Keyword(s):  
Heart Rate ◽  
Low Frequency ◽  
Heart Tissue ◽  
Fast Fourier Transformation ◽  
Receptor Subtypes ◽  
Wild Type ◽  
Frequency Domain Methods ◽  
Β2 Adrenergic Receptor ◽  
Β Adrenergic Receptors

β-Adrenergic receptors (β-ARs) play a major role in regulating heart rate (HR) and contractility in the intact cardiovascular system. Three subtypes (β1, β2, and β3) are expressed in heart tissue, and the role of each subtype in regulating cardiac function has previously been determined by using both pharmacological and gene-targeting approaches. However, previous studies have only examined the role of β-ARs in the macrolevel regulation of HR. We employed three knockout (KO) mouse lines, β1-KO, β2-KO, and β1/β2 double KO (DL-KO), to examine the role that β-AR subtypes play in HR variability (HRV) and in the sympathetic and parasympathetic inputs into HR control. Fast Fourier transformation (FFT) in frequency domain methods of ECG spectral analysis was used to resolve HRV into high- and low-frequency (HF and LF) powers. Resting HR (in beats/min) was decreased in β1-KO [488 (SD 27)] and DL-KO [495 (SD 12)] mice compared with wild-type [WT; 638 (SD 30)] or β2-KO [656 (SD 51)] ( P < 0.0005) mice. Mice lacking β1-ARs (β1-KO and DL-KO) had increased HRV (as illustrated by the standard deviation of normal R-R intervals) and increased normalized HF and LF powers compared with mice with intact β1-ARs (WT and β2-KO). These results demonstrate the differential role of β-AR subtypes in regulating autonomic signaling.

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