Gill denervation eliminates the barostatic reflex in a neotropical teleost, the tambaqui (Colossoma macropomum)

Abstract

The baroreflex is one of the most important regulators of cardiovascular homeostasis in vertebrates. It begins with the monitoring of arterial pressure by baroreceptors, which constantly provide the central nervous system with afferent information about the status of this variable. Any change in arterial pressure relative to its normal state triggers autonomic responses, which are characterized by an inversely proportional change in heart rate and systemic vascular resistance and which tend to restore pressure normality. Although the baroreceptors have been located in mammals and other terrestrial vertebrates, their location in fish is still not completely clear and remains quite controversial. Thus, the objective of this study was to locate the baroreceptors in a teleost, the Colossoma macropomum. To do so, the occurrence and efficiency of the baroreflex were both analyzed when this mechanism was induced by pressure imbalancements in intact fish (IN), first-gill-denervated fish (G1), and total-gill-denervated fish (G4). The pressure imbalances were initiated through the administration of the α1-adrenergic agonist phenylephrine (100 µg kg(-1)) and the α1-adrenergic antagonist prazosin (1 mg kg(-1)). The baroreflex responses were then analyzed using an electrocardiogram that allowed for the measurement of the heart rate, the relationship between pre- and post-pharmacological manipulation heart rates, the time required for maximum chronotropic baroreflex response, and total heart rate variability. The results revealed that the barostatic reflex was attenuated in the G1 group and nonexistent in G4 group, findings which indicate that baroreceptors are exclusively located in the gill arches of C. macropomum.

Autonomic control of cardiovascular adjustments associated with orthostasis in the scansorial snakeBoa constrictor

“…2C,D). This indicates a reduction in the efficiency of this baroreflex f H adjustment (Armelin et al, 2016), and it may be the reason why the P A of atropinised animals reached values lower than those of untreated animals when tilted to 30 and 60 deg. In contrast, double cardiac autonomic receptor blockade eradicated changes in f H during inclinations ( Fig.…”

Central and Peripheral Effects of Urotensin II and Urotensin II-Related Peptides on Cardiac Baroreflex Sensitivity in Trout

“…In fish, the primary baroreceptor sites are the gills (Ristori and Dessaux, 1970 ; Nilsson and Sundin, 1998 ; Armelin et al, 2016 ). Afferent baroreceptive activity runs along the glossopharyngeal (IXth cranial nerve) and along the vagus (Xth cranial nerve) to reach the medulla oblongata.…”

The nonpharmacological sequence method provides a reliable evaluation of baroreflex sensitivity in fish

“…The location of baroreceptors within the fish gill remains unknown, so it is currently debated whether P VA or dorsal aortic blood pressure ( P DA ) best reflects the pressure sensed by the baroreceptors (Armelin et al, 2016; Bagshaw, 1985; Jones & Milsom, 1982; Sandblom et al, 2016; Sundin & Nilsson, 2002). Sandblom et al (2016) observed that intra‐arterial sodium nitroprusside administrations only induced very small P VA reductions in the common perch ( Perca fluviatilis ), but were associated with marked reflex tachycardia.…”

“…The baroreflex relies on negative feedback, where altered arterial blood pressure initiates proportional changes in cardiac pulse interval (PI) and systemic vascular conductance to restore pressure (Bagshaw, 1985; Chapleau, 2012; Hedrick et al, 2015; Sandblom & Axelsson, 2005; Van Vliet & West, 1994). Given its importance for cardiovascular regulation, the baroreflex has been characterized under a variety of circumstances in most groups of vertebrates (Armelin et al, 2014, 2016, 2019; Hagensen et al, 2010; La Rovere et al, 2008; Lee et al, 2002; Mueller et al, 2013; Zena et al, 2015; Zena, Dantonio, et al, 2016).…”