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James LE, Bertelsen MF, Wang T, Williams CJA. Impact of procedural handling on the physiological effects of alfaxalone anaesthesia in the ball python (Python regius). Comp Biochem Physiol A Mol Integr Physiol 2024; 297:111704. [PMID: 39038601 DOI: 10.1016/j.cbpa.2024.111704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 07/17/2024] [Accepted: 07/17/2024] [Indexed: 07/24/2024]
Abstract
To describe the cardiovascular changes following intramuscular (handled) and intravascular (undisturbed, via intraarterial catheter) alfaxalone administration, we studied 20 healthy ball pythons (Python regius) in a randomised, prospective study. The pythons were instrumented with occlusive arterial catheters to facilitate undisturbed, continuous monitoring of heart rate and blood pressure. Six pythons were administered intramuscular (IM) saline, followed by 20 mg/kg IM alfaxalone, and were manually restrained for both injections. Six pythons received intraarterial (IA) saline, followed by 10 mg/kg IA alfaxalone, and remained undisturbed for both injections. Arterial blood samples were taken at 0, 12 and 60 min post-injection, and heart rate and blood pressure were recorded for 60 min. The remaining eight snakes received 20 mg/kg IM or 10 mg/kg IA alfaxalone (n = 4 per treatment) and were not handled for intubation 10 min post-injection, to examine the effects of handling during anaesthesia. IM administration of 20 mg/kg alfaxalone or an equivalent volume of saline elicited a profound tachycardia and hypertension, which recovered to resting values after 20 min. However, when 10 mg/kg alfaxalone or saline were injected IA, mild hypotension and a lower magnitude tachycardia occurred. Arterial PCO2 and PO2, pH and lactate concentrations did not change following IA alfaxalone, but an acidosis was observed during IM alfaxalone anaesthesia. There were no significant changes in plasma catecholamines and corticosterone among treatments. Handling for injection and during anaesthesia associated with intubation significantly affects cardiovascular parameters, whereas alfaxalone per se only elicits minor changes in cardiovascular physiology.
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Affiliation(s)
- Lauren E James
- Section for Zoophysiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Mads F Bertelsen
- Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Copenhagen, Denmark
| | - Tobias Wang
- Section for Zoophysiology, Department of Biology, Aarhus University, Aarhus, Denmark. https://twitter.com/Tobias_Wang_AU
| | - Catherine J A Williams
- Section for Zoophysiology, Department of Biology, Aarhus University, Aarhus, Denmark; Department of Animal and Veterinary Science, Aarhus University, Tjele, Denmark.
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2
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Braga VHDS, Armelin VA, Noll IG, Florindo LH, Milsom WK. Cardiorespiratory reflexes in white sturgeon (Acipenser transmontanus): Lack of cardiac baroreflex response to blood pressure manipulation? Comp Biochem Physiol A Mol Integr Physiol 2024; 288:111554. [PMID: 37989399 DOI: 10.1016/j.cbpa.2023.111554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 11/16/2023] [Accepted: 11/16/2023] [Indexed: 11/23/2023]
Abstract
Arterial pressure (Pa) regulation is essential to adequately distribute nutrients to metabolizing tissues, remove wastes and avoid lesions associated with hypertension. In vertebrates, short-term Pa regulation is achieved through the baroreflex, which elicits inversely proportional changes in heart rate (fH) and vascular resistance to restore Pa. The cardiac limb of this reflex has been reported in all vertebrate groups studied to date: teleosts, amphibians, snakes, lizards, crocodiles, birds and mammals - which led to the suggestion that the baroreflex is an ancient trait present in all vertebrate species. However, it is not clear whether more basal groups of vertebrates, such as cyclostomes, elasmobranchs and chondrosteans, manifest baroreflex regulation of fH. Thus, the aim of this study was to determine whether the white sturgeon (Acipenser transmontanus; Chondrostei: Acipenseridae) exhibits a cardiac baroreflex. To do so, we induced Pa perturbations through injections of phenylephrine, sodium nitroprusside (SNP) and saline solution (hypervolemia), and examined possible fH baroreflex responses. We also investigated whether fH responses triggered by fright and chemoreflex were present in this species, in order to confirm the potential of sturgeon to perform reflexive cardiac adjustments. The findings indicate that A. transmontanus exhibits reflex bradycardia in response to fright and chemoreceptor stimulation, illustrating its capacity for short-term cardiac regulation. However, this species does not display baroreflex control of fH across its physiological range. This dissociation suggests that while the nervous and cardiovascular systems of A. transmontanus are primed for rapid reflex responses, a cardiac baroreflex mechanism remains absent.
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Affiliation(s)
- Victor Hugo da Silva Braga
- Department of Biological Sciences, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil. https://twitter.com/b07855682
| | - Vinicius Araújo Armelin
- Department of Physiology, University of São Paulo (USP), Rua do Matão - Travessa 14 - N. 101, Cidade Universitária, São Paulo, SP 05508-090, Brazil
| | - Igor Guagnoni Noll
- Department of Biological Sciences, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil
| | - Luiz Henrique Florindo
- Department of Biological Sciences, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil; Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Rodovia Washington Luiz, km 235, São Carlos, SP 13565-905, Brazil; Aquaculture Centre (CAUNESP), São Paulo State University (UNESP), Rodovia Prof. Paulo Donato Castellane, n/n, Jaboticabal, SP 14884-900, Brazil.
| | - William Kenneth Milsom
- Department of Zoology, University of British Columbia (UBC), 4200 - 6270 University Blvd, V6T 1Z4 Vancouver, Canada
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Tavares D, da Silva Matos SLB, Duran LM, Castro SA, Taylor EW, Filogonio R, Fernandes MN, Leite CA. Baroreflex responses of decerebrate rattlesnakes (Crotalus durissus) are comparable to awake animals. Comp Biochem Physiol A Mol Integr Physiol 2022; 273:111286. [DOI: 10.1016/j.cbpa.2022.111286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 07/29/2022] [Accepted: 08/02/2022] [Indexed: 11/30/2022]
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Thermal acclimation and acute temperature effects on cardiac barostatic reflexes in rainbow trout (Oncorhynchus mykiss). J Therm Biol 2022; 109:103315. [DOI: 10.1016/j.jtherbio.2022.103315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/26/2022] [Accepted: 08/24/2022] [Indexed: 11/17/2022]
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5
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Wang T, Abe AS, Cruz-Neto AP, Andrade DV, Taylor EW. Maintained barostatic regulation of heart rate in digesting snakes (Boa constrictor). J Exp Biol 2021; 224:271931. [PMID: 34427663 DOI: 10.1242/jeb.242202] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 08/18/2021] [Indexed: 02/03/2023]
Abstract
When snakes digest large meals, heart rate is accelerated by withdrawal of vagal tone and an increased non-adrenergic-non-cholinergic tone that seems to stem from circulating blood-borne factors exerting positive chronotropic effects. To investigate whether this tonic elevation of heart rate impairs the ability for autonomic regulation of heart during digestion, we characterised heart rate responses to pharmacological manipulation of blood pressure in the snake Boa constrictor through serial injections of sodium nitroprusside and phenylephrine. Both fasting and digesting snakes responded with a robust tachycardia to hypotension induced by sodium nitroprusside, with digesting snakes attaining higher maximal heart rates than fasting snakes. Both fasting and digesting snakes exhibited small reductions of the cardiac chronotropic response to hypertension, induced by injection of phenylephrine. All heart rate changes were abolished by autonomic blockade with the combination of atropine and propranolol. The digesting snakes retained the capacity for compensatory heart rate responses to hypotension, despite their higher resting values, and the upward shift of the barostatic response curve enables snakes to maintain the cardiac limb of barostatic regulation for blood pressure regulation.
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Affiliation(s)
- Tobias Wang
- Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark.,Department of Biodiversity, State University of São Paulo, PO BOX 199 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Augusto S Abe
- Department of Biodiversity, State University of São Paulo, PO BOX 199 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Ariovaldo P Cruz-Neto
- Department of Biodiversity, State University of São Paulo, PO BOX 199 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Denis V Andrade
- Department of Biodiversity, State University of São Paulo, PO BOX 199 13506-900, Rio Claro, Sao Paulo, Brazil
| | - Edwin W Taylor
- Department of Biodiversity, State University of São Paulo, PO BOX 199 13506-900, Rio Claro, Sao Paulo, Brazil.,School of Biosciences, The University of Birmingham, Edgbaston B15 2TT, England
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Baroreflex responses to activity at different temperatures in the South American rattlesnake, Crotalus durissus. J Comp Physiol B 2021; 191:917-925. [PMID: 34363512 DOI: 10.1007/s00360-021-01396-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 07/15/2021] [Accepted: 07/30/2021] [Indexed: 10/20/2022]
Abstract
In humans, physical exercise imposes narrower limits for the heart rate (fH) response of the baroreflex, and vascular modulation becomes largely responsible for arterial pressure regulation. In undisturbed reptiles, the baroreflex-related fH alterations at the operating point (Gop) decreases at elevated body temperatures (Tb) and the vascular regulation changes accordingly. We investigated how the baroreflex of rattlesnakes, Crotalus durissus, is regulated during an activity at different Tb, expecting that activity would reduce the capacity of the cardiac baroreflex neural pathway to buffer arterial pressure fluctuations while being compensated by the vascular neural pathway regulation. Snakes were catheterized for blood pressure assessment at three different Tb: 15, 20 and 30 °C. Data were collected before and after activity at each Tb. Baroreflex gain (Gop) was assessed with the sequence method; the vascular limb, with the time constant of pressure decay (τ), using the two-element Windkessel equation. Both Gop and τ reduced when Tb increased. Activity also reduced Gop and τ in all Tb. The relationship between τ and pulse interval (τ/PI) was unaffected by the temperature at resting snakes, albeit it reduced after activity at 20 °C and 30 °C. The unchanged τ/PI and normalized Gop at different Tb indicated those variables are actively adjusted to work at different fH and pressure conditions at rest. Our data suggest that during activity, the baroreflex-related fH response is attenuated and hypertension is buffered by a disproportional increase in the rate which pressure decays during diastole. This compensation seems especially important at higher Tb where Gop is already low.
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Rocha GC, Castro SA, Taylor EW, Tavares D, Leite CAC. A Decerebrate Preparation of the Rattlesnake, Crotalus durissus, Provides an Experimental Model for Study of Autonomic Modulation of the Cardiovascular System in Reptiles. Physiol Biochem Zool 2021; 94:269-285. [PMID: 34142933 DOI: 10.1086/714973] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractThe South American rattlesnake, Crotalus durissus, has been successfully used as an experimental model to study control of the cardiovascular system in squamate reptiles. Recent technical advances, including equipment miniaturization, have lessened the impact of instrumentation on in vivo recordings, and an increased range of anesthetic drugs has improved recording conditions for in situ preparations. Nevertheless, any animal-based experimental approach has to manage limitations regarding the avoidance of pain and stress the stability of the preparation and duration of experiments and the potentially overriding effects of anesthesia. To address such aspects, we tested a new experimental preparation, the decerebrate rattlesnake, in a study of the autonomic control of cardiovascular responses following the removal of general anesthesia. The preparation exhibited complex cardiovascular adjustments to deal with acute increases in venous return (caused by tail lifting), to compensate for blood flow reduction in the cephalic region (caused by head lifting), for body temperature control (triggered by an external heating source), and in response to stimulation of chemoreceptors (triggered by intravenous injection of NaCN). The decerebrate preparation retained extensive functional integrity of autonomic centers, and it was suitable for monitoring diverse cardiac and vascular variables. Furthermore, reanesthetizing the preparation markedly blunted cardiovascular performance. Isoflurane limited the maintenance of recovered cardiovascular variables in the prepared animal and reduced or abolished the observed cardiovascular reflexes. This preparation enables the recording of multiple concomitant cardiovascular variables for the study of mechanistic questions regarding the central integration of autonomic reflex responses in the absence of anesthesia.
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Filogonio R, Dubansky BD, Dubansky BH, Wang T, Elsey RM, Leite CAC, Crossley DA. Arterial wall thickening normalizes arterial wall tension with growth in American alligators, Alligator mississippiensis. J Comp Physiol B 2021; 191:553-562. [PMID: 33629153 DOI: 10.1007/s00360-021-01353-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/21/2021] [Accepted: 01/28/2021] [Indexed: 01/21/2023]
Abstract
Arterial wall tension increases with luminal radius and arterial pressure. Hence, as body mass (Mb) increases, associated increases in radius induces larger tension. Thus, it could be predicted that high tension would increase the potential for rupture of the arterial wall. Studies on mammals have focused on systemic arteries and have shown that arterial wall thickness increases with Mb and normalizes tension. Reptiles are good models to study scaling because some species exhibit large body size range associated with growth, thus, allowing for ontogenetic comparisons. We used post hatch American alligators, Alligator mississippiensis, ranging from 0.12 to 6.80 kg (~ 60-fold) to investigate how both the right aortic arch (RAo) and the left pulmonary artery (LPA) change with Mb. We tested two possibilities: (i) wall thickness increases with Mb and normalizes wall tension, such that stress (stress = tension/thickness) remains unchanged; (ii) collagen content scales with Mb and increases arterial strength. We measured heart rate and systolic and mean pressures from both systemic and pulmonary circulations in anesthetized animals. Once stabilized alligators were injected with adrenaline to induce a physiologically relevant increase in pressure. Heart rate decreased and systemic pressures increased with Mb; pulmonary pressures remained unchanged. Both the RAo and LPA were fixed under physiological hydrostatic pressures and displayed larger radius, wall tension and thickness as Mb increased, thus, stress was independent from Mb; relative collagen content was unchanged. We conclude that increased wall thickness normalizes tension and reduces the chances of arterial walls rupturing in large alligators.
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Affiliation(s)
- Renato Filogonio
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil.
| | - Benjamin D Dubansky
- Department of Biological Sciences, Developmental Integrative Biology Cluster, University of North Texas, Denton, TX, 76203-5220, USA
| | - Brooke H Dubansky
- Department of Medical Laboratory Sciences and Public Health, Tarleton State University, Fort Worth, TX, USA
| | - Tobias Wang
- Section for Zoophysiology, Department of Biosciences, Aarhus University, 8000, Aarhus C, Denmark
| | - Ruth M Elsey
- Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, LA, 70643, USA
| | - Cléo A C Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil
| | - Dane A Crossley
- Department of Biological Sciences, Developmental Integrative Biology Cluster, University of North Texas, Denton, TX, 76203-5220, USA
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9
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Lopes AG, Monteiro DA, Kalinin AL. Effects of change in temperature on the cardiac contractility of broad-snouted caiman (Caiman latirostris) during digestion. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:417-425. [PMID: 33773091 DOI: 10.1002/jez.2457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/12/2021] [Accepted: 03/13/2021] [Indexed: 11/07/2022]
Abstract
In many reptiles, digestion has been associated with the selection of higher body temperatures, the so-called post-prandial thermophilic response. This study aimed to investigate the excitation-contraction (E-C) coupling in postprandial broad-snouted caimans (Caiman latirostris) in response to acute warming within a preferred body temperature range of crocodiles. Isometric preparations subjected to a temperature transition from 25°C to 30°C were used to investigate myocardial contractility of postprandial caimans, that is, 48 h after the animals ingested a rodent meal corresponding to 15% of body mass. The caiman heart exhibits a negative force-frequency relationship that is independent of the temperature. At 25°C, cardiac muscle was able to maintain a constant force up to 36 bpm, above which it decreased significantly, reaching minimum values at the highest frequency of 84 bpm. Moreover, E-C coupling is predominantly dependent on transsarcolemmal Ca2+ transport denoted by the lack of significant ryanodine effects on force generation. On the contrary, ventricular strips at 30°C were able to sustain the cardiac contractility at higher pacing frequencies (from 12 to 144 bpm) due to an important role of Na+ /Ca2+ exchanger in Ca2+ cycling, as indicated by the decay of the post-rest contraction, and a significant contribution of the sarcoplasmic reticulum above 72 bpm. Our results demonstrated that the myocardium of postprandial caimans exhibits a significant degree of thermal plasticity of E-C coupling during acute warming. Therefore, myocardial contractility can be maximized when postprandial broad-snouted caimans select higher body temperatures (preferred temperature zone) following feeding.
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Affiliation(s)
- André G Lopes
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil.,Joint Graduate Program in Physiological Sciences, Federal University of São Carlos-UFSCar/São Paulo State University, UNESP Campus Araraquara, Araraquara, São Paulo, Brazil
| | - Diana A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - Ana L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
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10
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Armelin VA, Braga VHDS, Teixeira MT, Guagnoni IN, Wang T, Florindo LH. The baroreflex in aquatic and amphibious teleosts: Does terrestriality represent a significant driving force for the evolution of a more effective baroreflex in vertebrates? Comp Biochem Physiol A Mol Integr Physiol 2021; 255:110916. [PMID: 33545361 DOI: 10.1016/j.cbpa.2021.110916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 01/24/2021] [Accepted: 01/25/2021] [Indexed: 10/22/2022]
Abstract
All vertebrates have baroreflexes that provide fast regulation of arterial blood pressure (PA) to maintain adequate tissue perfusion and avoid vascular lesions from excessive pressures. The baroreflex is a negative feedback loop, where altered PA results in reciprocal changes in heart rate (fH) and systemic vascular conductance to restore pressure. In terrestrial environments, gravity usually leads to blood pooling in the lower body reducing venous return, cardiac filling, cardiac output and PA. Conversely, in aquatic environments, the hydrostatic pressure of surrounding water mitigates blood pooling and prevents vascular distensions. In this context, we aimed to test the hypothesis that vertebrate species that were exposed to gravity-induced hemodynamic disturbances throughout their evolutionary histories have a more effective barostatic reflex than those that were not. We examined the cardiac baroreflex of fish that perform (Clarias gariepinus and Hoplerythrinus unitaeniatus) and do not perform (Hoplias malabaricus and Oreochromis niloticus) voluntary terrestrial sojourns, using pharmacological manipulations of PA to characterize reflex changes in fH using a four-variable sigmoidal logistic function (i.e. the "Oxford technique"). Our results revealed that amphibious fish exhibit higher baroreflex gain and responsiveness to hypotension than strictly aquatic fish, suggesting that terrestriality and the gravitational circulatory stresses constitute a relevant driving force for the evolution of a more effective baroreflex in vertebrates. We also demonstrate that strictly aquatic teleosts have considerable baroreflex gain, supporting the view that the baroreflex is an ancient cardiovascular trait that appeared before vertebrates colonized the gravity-dominated realm of land.
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Affiliation(s)
- Vinicius Araújo Armelin
- Department of Physiology, Institute of Biosciences, University of São Paulo (USP), Rua do Matão, Travessa 14, 321, São Paulo, SP, 05508-090, Brazil; Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo 2265, São José do Rio Preto, SP, 15054-000, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT - FAPESP/CNPq), São Paulo, Brazil.
| | - Victor Hugo da Silva Braga
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo 2265, São José do Rio Preto, SP, 15054-000, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT - FAPESP/CNPq), São Paulo, Brazil
| | - Mariana Teodoro Teixeira
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo 2265, São José do Rio Preto, SP, 15054-000, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT - FAPESP/CNPq), São Paulo, Brazil
| | - Igor Noll Guagnoni
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo 2265, São José do Rio Preto, SP, 15054-000, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT - FAPESP/CNPq), São Paulo, Brazil
| | - Tobias Wang
- Section for Zoophysiology, Department of Bioscience, Aarhus University (AU), C. F. Møllers Allé 3, Aarhus, 8000 Aarhus C, Denmark; National Institute of Science and Technology in Comparative Physiology (INCT - FAPESP/CNPq), São Paulo, Brazil
| | - Luiz Henrique Florindo
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo 2265, São José do Rio Preto, SP, 15054-000, Brazil; Aquaculture Center (CAUNESP), São Paulo State University (UNESP), Rodovia Prof. Paulo Donato Castellane n/n, Jaboticabal, SP, 14884-900, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT - FAPESP/CNPq), São Paulo, Brazil
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11
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Armelin VA, Braga VHDS, Teixeira MT, Guagnoni IN, Wang T, Florindo LH. The nonpharmacological sequence method provides a reliable evaluation of baroreflex sensitivity in fish. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:348-358. [PMID: 33503334 DOI: 10.1002/jez.2448] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 12/22/2020] [Accepted: 01/08/2021] [Indexed: 11/10/2022]
Abstract
The most commonly used technique to study the barostatic regulation of blood pressure in ectothermic vertebrates consists of determining the heart rate response to pharmacological manipulations of blood pressure, the so-called "Oxford method." Although well established, the Oxford method has some important limitations, such as induction of hypervolemia in small animals and undesired effects of vasoactive drugs on central and peripheral baroreflex components. As an alternative, the sequence method, which consists in the computerized evaluation of naturally-occurring baroreflex adjustments of heart rate without the need for pharmacological administrations, was developed to study baroreflexes. In the present study, we compare this sequence method with the Oxford technique in two teleost species with different life styles, and we assess the optimal software configuration for the employment of the sequence method in fish. Calculation of baroreflex gain through the sequence method was adequate and reliable when the software was configured to search for baroreflex sequences with a minimum length of three cardiac cycles with a delay of one cardiac cycle between fluctuations in mean ventral aortic blood pressure and reflex changes in pulse interval. When properly configured, the sequence and the Oxford methods yielded similar determinations of the baroreflex gain in fish.
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Affiliation(s)
- Vinicius A Armelin
- Department of Physiology, University of São Paulo (USP), São Paulo, SP, Brazil.,Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, SP, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, SP, Brazil
| | - Victor H da Silva Braga
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, SP, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, SP, Brazil
| | - Mariana T Teixeira
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, SP, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, SP, Brazil
| | - Igor N Guagnoni
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, SP, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, SP, Brazil
| | - Tobias Wang
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, SP, Brazil.,Section for Zoophysiology, Department of Bioscience, Aarhus University (AU), Aarhus, Denmark
| | - Luiz H Florindo
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, SP, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, SP, Brazil.,Aquaculture Center (CAUNESP), São Paulo State University (UNESP), Jaboticabal, SP, Brazil
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12
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Filogonio R, Orsolini KF, Oda GM, Malte H, Leite CAC. Baroreflex gain and time of pressure decay at different body temperatures in the tegu lizard, Salvator merianae. PLoS One 2020; 15:e0242346. [PMID: 33227002 PMCID: PMC7682859 DOI: 10.1371/journal.pone.0242346] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/01/2020] [Indexed: 12/20/2022] Open
Abstract
Ectotherms may experience large body temperature (Tb) variations. Higher Tb have been reported to increase baroreflex sensitivity in ectotherm tetrapods. At lower Tb, pulse interval (PI) increases and diastolic pressure decays for longer, possibly resulting in lower end-diastolic pressures and mean arterial pressures (Pm). Additionally, compensatory baroreflex-related heart rate modulation (i.e. the cardiac branch of the baroreflex response) is delayed due to increased PI. Thus, low Tb is potentially detrimental, leading to cardiovascular malfunctioning. This raises the question on how Pm is regulated in such an adverse condition. We investigated the baroreflex compensations that enables tegu lizards, Salvator merianae, to maintain blood pressure homeostasis in a wide Tb range. Lizards had their femoral artery cannulated and pressure signals recorded at 15°C, 25°C and 35°C. We used the sequence method to analyse the heart rate baroreflex-related corrections to spontaneous pressure fluctuations at each temperature. Vascular adjustments (i.e. the peripheral branch) were assessed by calculating the time constant for arterial pressure decay (τ)—resultant from the action of both vascular resistance and compliance—by fitting the diastolic pressure descent to the two-element Windkessel equation. We observed that at lower Tb, lizards increased baroreflex gain at the operating point (Gop) and τ, indicating that the diastolic pressure decays at a slower rate. Gop normalized to Pm and PI, as well as the ratio τ/PI, did not change, indicating that both baroreflex gain and rate of pressure decay are adjusted according to PI lengthening. Consequently, pressure parameters and the oscillatory power fraction (an index of wasted cardiac energy) were unaltered by Tb, indicating that both Gop and τ modulation are crucial for cardiovascular homeostasis.
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Affiliation(s)
- Renato Filogonio
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
- * E-mail:
| | - Karina F. Orsolini
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - Gustavo M. Oda
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - Hans Malte
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus C, Denmark
| | - Cléo A. C. Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
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13
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Cardiovascular and ventilatory interactions in the facultative air-breathing teleost Pangasianodon hypophthalmus. J Comp Physiol B 2019; 189:425-440. [DOI: 10.1007/s00360-019-01225-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 05/20/2019] [Accepted: 06/24/2019] [Indexed: 02/07/2023]
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14
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Dhyani N, Saidullah B, Fahim M, Omanwar S. Fenofibrate ameliorates neural, mechanical, chemical, and electrical alterations in the murine model of heart failure. Hum Exp Toxicol 2019; 38:1183-1194. [PMID: 31256679 DOI: 10.1177/0960327119860173] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Heart failure (HF) is a leading cause of hospitalization across the world and is known to cause ill-health and heavy economic losses. In the present study, a rat model of isoproterenol (ISO, 85 mg/kg subcutaneously for two subsequent days) induced HF was developed. ISO induces HF by its direct effect, that is, rise in left ventricular end-diastolic pressure (mechanical) and indirectly by altering the baroreflex (neural), electrocardiography (electrical), and development of oxidative stress and hyperlipidemia (chemical). Fenofibrate, a hypolipidemic drug, which ameliorates myocardial energy metabolism was seen to improve the both ISO-induced oxidative stress and lipid profile and consequently improved Baroreflex Sensitivity (BRS), partial ventricular functions, and cardiac hypertrophy. Therefore, our result suggests that fenofibrate treatment protected the heart by alleviating the ISO-induced effects, that is, neural, mechanical, electrical, and chemical alterations.
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Affiliation(s)
- N Dhyani
- 1 Department of Life Sciences, School of Sciences, Indira Gandhi National Open University (IGNOU), Maidan Garhi, New Delhi, India
| | - B Saidullah
- 1 Department of Life Sciences, School of Sciences, Indira Gandhi National Open University (IGNOU), Maidan Garhi, New Delhi, India
| | - M Fahim
- 2 Department of Physiology, Hamdard Institute of Medical Sciences and Research, Jamia Hamdard (Hamdard University), Hamdard Nagar, New Delhi, India
| | - S Omanwar
- 1 Department of Life Sciences, School of Sciences, Indira Gandhi National Open University (IGNOU), Maidan Garhi, New Delhi, India
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15
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Filogonio R, Orsolini KF, Castro SA, Oda GM, Rocha GC, Tavares D, Abe AS, Leite CAC. Evaluation of the sequence method as a tool to assess spontaneous baroreflex in reptiles. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2019; 331:374-381. [DOI: 10.1002/jez.2273] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 01/22/2023]
Affiliation(s)
- Renato Filogonio
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
| | - Karina F. Orsolini
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
| | - Samanta A. Castro
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
| | - Gustavo M. Oda
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
| | - Gabriella C. Rocha
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
| | - Driele Tavares
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
| | - Augusto S. Abe
- Department of Zoology; State University of São Paulo (UNESP); Rio Claro São Paulo Brazil
| | - Cléo A. C. Leite
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos São Paulo Brazil
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16
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Joyce W, White DW, Raven PB, Wang T. Weighing the evidence for using vascular conductance, not resistance, in comparative cardiovascular physiology. J Exp Biol 2019; 222:222/6/jeb197426. [DOI: 10.1242/jeb.197426] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
ABSTRACT
Vascular resistance and conductance are reciprocal indices of vascular tone that are often assumed to be interchangeable. However, in most animals in vivo, blood flow (i.e. cardiac output) typically varies much more than arterial blood pressure. When blood flow changes at a constant pressure, the relationship between conductance and blood flow is linear, whereas the relationship between resistance and blood flow is non-linear. Thus, for a given change in blood flow, the change in resistance depends on the starting point, whereas the attendant change in conductance is proportional to the change in blood flow regardless of the starting conditions. By comparing the effects of physical activity at different temperatures or between species – concepts at the heart of comparative cardiovascular physiology – we demonstrate that the difference between choosing resistance or conductance can be marked. We also explain here how the ratio of conductance in the pulmonary and systemic circulations provides a more intuitive description of cardiac shunt patterns in the reptilian cardiovascular system than the more commonly used ratio of resistance. Finally, we posit that, although the decision to use conductance or resistance should be made on a case-by-case basis, in most circumstances, conductance is a more faithful portrayal of cardiovascular regulation in vertebrates.
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Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Daniel W. White
- School of Arts & Sciences, University of Houston-Victoria, Victoria, TX 77901, USA
| | - Peter B. Raven
- Department of Physiology and Anatomy, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Tobias Wang
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
- Aarhus Institute of Advanced Sciences (AIAS), Aarhus University, 8000 Aarhus C, Denmark
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17
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Young BA, Adams J, Segal S, Kondrashova T. Hemodynamics of tonic immobility in the American alligator (Alligator mississippiensis) identified through Doppler ultrasonography. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018; 204:953-964. [PMID: 30259097 DOI: 10.1007/s00359-018-1293-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 09/11/2018] [Accepted: 09/21/2018] [Indexed: 11/28/2022]
Abstract
American alligators (Alligator mississippiensis) held inverted exhibit tonic immobility, combining unresponsiveness with flaccid paralysis. We hypothesize that inverting the alligator causes a gravitationally promoted increase in right aortic blood flowing through the foramen of Panizza, with a concurrent decrease in blood flow through the primary carotid, and thereby of cerebral perfusion. Inverting the alligator results in displacement of the liver, post-pulmonary septum, and the heart. EKG analysis revealed a significant decrease in heart rate following inversion; this decrease was maintained for approximately 45 s after inversion which is in general agreement with the total duration of tonic immobility in alligators (49 s). Doppler ultrasonography revealed that following inversion of the alligator, there was a reversal in direction of blood flow through the foramen of Panizza, and this blood flow had a significant increase in velocity (compared to the foraminal flow in the prone alligator). There was an associated significant decrease in the velocity of blood flow through the primary carotid artery once the alligator was held in the supine position. Tonic immobility in the alligator appears to be a form of vasovagal syncope which arises, in part, from the unique features of the crocodilian heart.
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Affiliation(s)
- Bruce A Young
- Department of Anatomy, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, MO, 63501, USA.
| | - James Adams
- Department of Anatomy, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, MO, 63501, USA
| | - Solomon Segal
- Department of Anatomy, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, MO, 63501, USA
| | - Tatyana Kondrashova
- Department of Family Medicine, Preventitive Medicine, and Community Health, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, MO, 63501, USA
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18
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Nelson D, Crossley DA, Elsey RM, Tate KB. Cardiovascular adjustments with egg temperature at 90% incubation in embryonic American alligators, Alligator mississippiensis. J Comp Physiol B 2018; 188:471-480. [PMID: 29380053 DOI: 10.1007/s00360-018-1144-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 12/15/2017] [Accepted: 01/03/2018] [Indexed: 01/14/2023]
Abstract
American alligators (Alligator mississippiensis) deposit eggs in a mound nest, potentially subjecting embryos to daily variations in temperature. Whilst adult crocodilian cardiovascular responses to changes in temperature have been investigated, similar studies in alligator embryos are limited. We investigated cardiovascular function of embryonic alligators during heating and cooling as well as at different temperatures. We measured arterial blood pressure (Pm) and heart rate (fH) in response to cooling (30-26 °C), heating (26-36 °C), followed by a reciprocal cooling event (36-26 °C) and assessed the cardiac baroreflex at 30 and 36 °C. Embryonic fH increased during heating events and decreased during cooling events, while embryos were hypotensive at 26 and 36 °C, although Pm did not differ between heating or cooling events. There was a clear temperature-dependent heart rate hysteresis at a given embryo's temperature, depending on whether embryos were cooling or heating. Cardiovascular regulation through the cardiac limb of the baroreflex was not affected by temperature, despite previous studies suggesting that vagal tone is present at both low and high temperatures.
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Affiliation(s)
- Derek Nelson
- Department of Biological Sciences, University of North Texas, 1155 Union Circle #305220, Denton, TX, 76203-5017, USA
| | - Dane A Crossley
- Department of Biological Sciences, University of North Texas, 1155 Union Circle #305220, Denton, TX, 76203-5017, USA.
| | - Ruth M Elsey
- Department of Wildlife and Fisheries, Grand Chenier, LA, USA
| | - Kevin B Tate
- Department of Biology, Truman State University Kirksville, Louisiana, MO, USA
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19
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Braga VHDS, Armelin VA, Teixeira MT, Abe AS, Rantin FT, Florindo LH. The Effects of Feeding on Cardiac Control of the Broad-Nosed Caiman (Caiman latirostris): The Role of the Autonomic Nervous System and NANC Factors. ACTA ACUST UNITED AC 2016; 325:524-531. [DOI: 10.1002/jez.2036] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/06/2016] [Accepted: 08/05/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Victor Hugo Da Silva Braga
- Department of Zoology and Botany; São Paulo State University (UNESP); São José do Rio Preto São Paulo Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq); São Paulo Brazil
| | - Vinicius Araújo Armelin
- Department of Zoology and Botany; São Paulo State University (UNESP); São José do Rio Preto São Paulo Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq); São Paulo Brazil
| | - Mariana Teodoro Teixeira
- Department of Zoology and Botany; São Paulo State University (UNESP); São José do Rio Preto São Paulo Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq); São Paulo Brazil
| | - Augusto Shinya Abe
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq); São Paulo Brazil
- Department of Zoology; São Paulo State University (UNESP); Rio Claro São Paulo Brazil
- Aquaculture Center (CAUNESP); São Paulo State University (UNESP); Jaboticabal São Paulo Brazil
| | - Francisco Tadeu Rantin
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq); São Paulo Brazil
- Department of Physiological Sciences; Federal University of São Carlos (UFSCar); São Carlos, São Paulo Brazil
| | - Luiz Henrique Florindo
- Department of Zoology and Botany; São Paulo State University (UNESP); São José do Rio Preto São Paulo Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq); São Paulo Brazil
- Aquaculture Center (CAUNESP); São Paulo State University (UNESP); Jaboticabal São Paulo Brazil
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20
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Zena LA, Dantonio V, Gargaglioni LH, Andrade DV, Abe AS, Bícego KC. Winter metabolic depression does not change arterial baroreflex control of heart rate in the tegu lizard (Salvator merianae). J Exp Biol 2016; 219:725-33. [DOI: 10.1242/jeb.129130] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 12/17/2015] [Indexed: 11/20/2022]
Abstract
Baroreflex regulation of blood pressure (BP) is important for maintaining appropriate tissue perfusion. Although temperature affects heart rate (fH) reflex regulation in some reptiles and toads, no data are available on the influence of temperature-independent metabolic states on baroreflex. The South American tegu lizard Salvator merianae exhibits a clear seasonal cycle of activity decreasing fH along with winter metabolic downregulation, independent of body temperature. Through pharmacological interventions (phenylephrine and sodium nitroprusside), the baroreflex control of fH was studied at ∼25°C in spring-summer and winter-acclimated tegus.
In winter lizards, resting and minimum fH were lower than in spring-summer animals (respectively, 13.3±0.82 vs 10.3±0.81 and 11.2±0.65 vs 7.97±0.88 beats.min−1), while no acclimation differences occurred in resting BP (5.14±0.38 vs 5.06±0.56 kPa), baroreflex gain (94.3±10.7 vs 138.7±30.3 %.kPa−1) and rate-pressure product (an index of myocardial activity). Vagal tone exceeded the sympathetic tone of fH especially in the winter group. Therefore, despite the lower fH, winter acclimation does not diminish the fH baroreflex responses nor rate-pressure product possibly because of increased stroke volume that may arise due to heart hypertrophy. Independent of acclimation, fH responded more to hypotension than to hypertension. This should imply that tegus, which have no pressure separation within the single heart ventricle, must have other protection mechanisms against pulmonary hypertension or oedema, presumably through lymphatic drainage and/or vagal vasoconstriction of pulmonary artery. Such a predominant fH reflex response to hypothension, previously observed in anurans, crocodilians and mammals, may be a common feature of tetrapods.
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Affiliation(s)
- Lucas A. Zena
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, Jaboticabal, São Paulo, 14884-900, Brazil
- National Institute of Science and Technology – Comparative Physiology (INCT- Fisiologia Comparada), Brazil
| | - Valter Dantonio
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, Jaboticabal, São Paulo, 14884-900, Brazil
- National Institute of Science and Technology – Comparative Physiology (INCT- Fisiologia Comparada), Brazil
| | - Luciane H. Gargaglioni
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, Jaboticabal, São Paulo, 14884-900, Brazil
- National Institute of Science and Technology – Comparative Physiology (INCT- Fisiologia Comparada), Brazil
| | - Denis V. Andrade
- Department of Zoology, Institute of Bioscience, São Paulo State University, Rio Claro, São Paulo, 13506-900, Brazil
- National Institute of Science and Technology – Comparative Physiology (INCT- Fisiologia Comparada), Brazil
| | - Augusto S. Abe
- Department of Zoology, Institute of Bioscience, São Paulo State University, Rio Claro, São Paulo, 13506-900, Brazil
- National Institute of Science and Technology – Comparative Physiology (INCT- Fisiologia Comparada), Brazil
| | - Kênia C. Bícego
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, Jaboticabal, São Paulo, 14884-900, Brazil
- National Institute of Science and Technology – Comparative Physiology (INCT- Fisiologia Comparada), Brazil
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21
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Sandblom E, Ekström A, Brijs J, Sundström LF, Jutfelt F, Clark TD, Adill A, Aho T, Gräns A. Cardiac reflexes in a warming world: Thermal plasticity of barostatic control and autonomic tones in a temperate fish. J Exp Biol 2016; 219:2880-2887. [DOI: 10.1242/jeb.140319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 07/04/2016] [Indexed: 12/24/2022]
Abstract
Thermal plasticity of cardiorespiratory function allows ectotherms like fish to cope with seasonal temperature changes and is critical for resilience to climate change. Yet, the chronic thermal effects on cardiovascular homeostatic reflexes in fish are little understood although this may have important implications for physiological performance and overall resilience to climate warming. We compared cardiac autonomic control and baroreflex regulation of heart rate in perch (Perca fluviatilis L.) from a reference area in the Baltic Sea at 18–19°C with conspecifics from the ‘Biotest enclosure’, a chronically heated ecosystem receiving warmed effluent water (24–25°C) from a nuclear power plant. Resting heart rates of Biotest fish displayed clear thermal compensation and were 58.3±2.3 beats min−1 compared with 52.4±2.6 beats min−1 in reference fish at their respective environmental temperatures (Q10: 1.2). The thermally-compensated heart rate of Biotest fish was a combined effect of elevated inhibitory cholinergic tone (105% in Biotest fish versus 70% in reference fish) and reduced intrinsic cardiac pacemaker rate. A barostatic response was evident in both groups, as pharmacologically-induced increases and decreases in blood pressure resulted in atropine-sensitive bradycardia and tachycardia, respectively. Yet, the tachycardia in Biotest fish was significantly greater, presumably due to the larger scope for vagal release. Acclimation of Biotest fish to 18°C for 3 weeks abolished differences in intrinsic heart rate and autonomic tones, suggesting considerable short-term thermal plasticity of cardiovascular control in this species. The heightened hypotensive tachycardia in Biotest perch may represent an important mechanism of ectothermic vertebrates that safeguards tissue perfusion pressure when tissue oxygen demand is elevated by environmental warming.
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Affiliation(s)
- E. Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - A. Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - J. Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - L. F. Sundström
- Department of Animal Ecology/Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
| | - F. Jutfelt
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | - T. D. Clark
- Australian Institute of Marine Science, Townsville, Queensland, Australia (current affiliation: University of Tasmania and CSIRO Agriculture Flagship, Hobart, Tasmania, Australia)
| | - A. Adill
- Institute of Coastal Research, Swedish University of Agricultural Sciences, Öregrund, Sweden
| | - T. Aho
- Institute of Coastal Research, Swedish University of Agricultural Sciences, Öregrund, Sweden
| | - A. Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden
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22
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Hedrick MS, McNew KA, Crossley DA. Baroreflex function in anurans from different environments. Comp Biochem Physiol A Mol Integr Physiol 2015; 179:144-8. [PMID: 25447736 DOI: 10.1016/j.cbpa.2014.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 10/03/2014] [Accepted: 10/03/2014] [Indexed: 10/24/2022]
Abstract
Anurans from terrestrial environments have an enhanced ability to maintain mean arterial blood pressure (P(m)) through lymph mobilization in response to desiccation or hemorrhage compared with semiaquatic or aquatic species. Because short term blood pressure homeostasis is regulated by arterial baroreceptors, we compared baroreflex function in three species of anurans that span a range of environments, dehydration tolerance and an ability to maintain P(m) with dehydration and hemorrhage. The cardiac limb of the baroreflex loop was studied using pharmacological manipulation of P(m) with phenylephrine and sodium nitroprusside (20–200 μg kg(− 1)), and the resulting changes in heart rate (f(H)) were quantitatively analyzed using a four-parameter sigmoidal logistic function. Resting P(m) in the aquatic species, Xenopus laevis, was 3.6 ± 0.3 kPa and was significantly less (P < 0.005) than for the semiaquatic species, Lithobates catesbeianus (4.1 ± 0.2 kPa), or the terrestrial species, Rhinella marina (4.7 ± 0.2 kPa). The maximal baroreflex gain was not different among the three species and ranged from 12.1 to 14.3 beats min( −1) kPa( −1) and occurred at P(m )ranging from 3.0 to 3.8 kPa, which were slightly below the resting P(m) for each species. Mean arterial blood pressures at rest in the three species were near the saturation point of the baroreflex curve which provides the animals with a greater fH response range to hypotensive, rather than hypertensive, changes in P(m). This is consistent with the hypothesis that arterial baroreceptors are key sensory components that allow anurans to maintain P(m) possibly by mobilization of lymphatic return in response to hypotension.
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23
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Hedrick MS, McNew KA, Crossley DA. Reprint of "Baroreflex function in anurans from different environments". Comp Biochem Physiol A Mol Integr Physiol 2015; 186:61-65. [PMID: 25843212 DOI: 10.1016/j.cbpa.2015.03.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 10/03/2014] [Accepted: 10/03/2014] [Indexed: 01/25/2023]
Abstract
Anurans from terrestrial environments have an enhanced ability to maintain mean arterial blood pressure (Pm) through lymph mobilization in response to desiccation or hemorrhage compared with semiaquatic or aquatic species. Because short term blood pressure homeostasis is regulated by arterial baroreceptors, we compared baroreflex function in three species of anurans that span a range of environments, dehydration tolerance and an ability to maintain Pm with dehydration and hemorrhage. The cardiac limb of the baroreflex loop was studied using pharmacological manipulation of Pm with phenylephrine and sodium nitroprusside (20-200μgkg(-1)), and the resulting changes in heart rate (fH) were quantitatively analyzed using a four-parameter sigmoidal logistic function. Resting Pm in the aquatic species, Xenopus laevis, was 3.6±0.3kPa and was significantly less (P<0.005) than for the semiaquatic species, Lithobates catesbeianus (4.1±0.2kPa), or the terrestrial species, Rhinella marina (4.7±0.2kPa). The maximal baroreflex gain was not different among the three species and ranged from 12.1 to 14.3beatsmin(-1)kPa(-1) and occurred at Pm ranging from 3.0 to 3.8kPa, which were slightly below the resting Pm for each species. Mean arterial blood pressures at rest in the three species were near the saturation point of the baroreflex curve which provides the animals with a greater fH response range to hypotensive, rather than hypertensive, changes in Pm. This is consistent with the hypothesis that arterial baroreceptors are key sensory components that allow anurans to maintain Pm possibly by mobilization of lymphatic return in response to hypotension.
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Affiliation(s)
- Michael S Hedrick
- Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA.
| | - Kadi A McNew
- Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA
| | - Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA
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24
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Acute and chronic temperature effects on cardiovascular regulation in the red-eared slider (Trachemys scripta). J Comp Physiol B 2015; 185:401-11. [PMID: 25774046 DOI: 10.1007/s00360-015-0896-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 02/13/2015] [Accepted: 02/27/2015] [Indexed: 10/23/2022]
Abstract
Acute and chronic changes in ambient temperature alter several aspects of reptilian physiology. We investigated the effects of each type of temperature change on reptilian cardiovascular regulation in red-eared slider turtles (Trachemys scripta), a species known to experience marked seasonal changes in ambient temperature. Turtles were instrumented with occlusive catheters in the femoral artery and vein. Following an acclimation period of 10 days at 13 °C (13(1)), cardiovascular responses to adrenaline, and the cardiac limb of the baroreflex were quantified. Ambient temperature was then reduced 1 °C day(-1) until 3 °C was reached (3(1)). Turtles were maintained at this temperature for 1-week before cardiovascular responses were reassessed. Turtles were then gradually (1 °C day(-1)) returned to an ambient temperature of 13 °C, (13(2)). After a 1-week re-acclimation period, cardiovascular responses were again determined. Finally, 1-week post-pharmacological manipulation of turtles in the 13(2) treatment, ambient temperature was reduced to 3 °C over 24 h (3(2)), and cardiovascular responses were again assessed. Temperature reduction from 13(1) to 3(1) decreased mean arterial blood pressure (P(m)) and heart rate (f(H)) by ~38 and ~63%, respectively. Acute temperature reduction, from 13(2) to 3(2), decreased f(H) similarly, ~66%; however, while P(m) decreased ~28%, this was not significantly different than P(m) at 13(2). The adrenaline injections increased f(H) ranging from 90 to 170% at 13 °C which was a greater change than that observed at 3 °C ranging from a 40 to 70% increase. The increase in P m at the lowest dose of adrenaline did not differ across the temperature treatment groups. The operational point (set-point) P(m) of the baroreflex was decreased similarly by both methods of temperature reduction (3(1) or 3(2)). Further, a hypertensive cardiac baroreflex was absent in the majority of the animals studied independent of temperature. Baroreflex gain and normalized gain based on individual estimates of the relationship were decreased by temperature reduction similarly. Collectively, the data suggest that red-eared slider turtles modulate (down-regulate) some cardiovascular control mechanisms during reduced ambient temperature.
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25
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Temperature effects on baroreflex control of heart rate in the toad, Rhinella schneideri. Comp Biochem Physiol A Mol Integr Physiol 2015; 179:81-8. [DOI: 10.1016/j.cbpa.2014.09.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 09/01/2014] [Accepted: 09/18/2014] [Indexed: 11/24/2022]
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