Baroreflex function in anurans from different environments

Hedrick, Michael S.; McNew, Kadi A.; Crossley, Dane A.

doi:10.1016/j.cbpa.2014.10.001

Cited by 15 publications

(17 citation statements)

References 34 publications

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“…5). In agreement with the ability of anurans to respond to hypotension primarily by increasing f H (Hedrick et al, 2015;Zena et al, 2015), R. schneideri also exhibited a prominent ventilatory response to reductions rather than increases in blood pressure. This provides correlational data for the ability of anurans to use their lungs to regulate blood volume ; in addition, it contributes to a prevailing view that amphibians strongly defend short-term blood pressure imbalances against low pressure events (Hedrick et al, 2015;Zena et al, 2015).…”

Section: Temperature Effects On Cardiorespiratory Reflex Responsessupporting

confidence: 64%

“…The ability to mount reflex f H responses mainly to hypotension in anurans accounts for most of the f H reflex responses due to changes in blood pressure (Hedrick et al, 2015;Zena et al, 2015) and can be strongly affected by the inability to further increase f H when the animal has an already elevated baseline value. Such a situation can be encountered by the animal at very high temperatures (>35°C; Overgaard et al, 2012) or during enforced activity (Wahlqvist and Campbell, 1988); the latter is already known to reset the baroreflex to higher f H and P MA values in humans (Norton et al, 1999).…”

Section: Temperature Effects On Cardiorespiratory Reflex Responsesmentioning

confidence: 99%

“…The afferent baroreceptor information is then relayed to and integrated in the central nervous system (CNS), where baroreflex buffering capacity is achieved by reflexively altering heart rate ( f H ) and vascular resistance (Altimiras et al, 1998;Bianchi-da-Silva et al, 2000;Sandblom and Axelsson, 2005;Hedrick et al, 2015;Zena et al, 2015Zena et al, , 2016. Besides cardiovascular responses, the baroreflex also influences respiratory function in mammals (for a review, see McMullan and Pilowsky, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Zena

Silva

Gargaglioni

et al. 2016

Journal of Experimental Biology

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Anurans regulate short-term oscillations in blood pressure through changes in heart rate ( f H ), vascular resistance and lymphatic f H . Lung ventilation in anurans is linked to blood volume homeostasis by facilitating lymph return to the cardiovascular system. We hypothesized that the arterial baroreflex modulates pulmonary ventilation in the cururu toad Rhinella schneideri, and that this relationship is temperature dependent. Pharmacologically induced hypotension (sodium nitroprusside) and hypertension (phenylephrine) increased ventilation (25°C: 248.7±25.7 ml kg −1 min; 35°C: 351.5± 50.2 ml kg) and decreased ventilation (25°C: 9.0± 6.6 ml kg , respectively; negative values indicate an inverse relationship between blood pressure and ventilation (or breathing frequency), i.e. as blood pressure increases, ventilation decreases, and vice versa], while temperature had no effect on these sensitivities. Hyperoxia (30%; 25°C) diminished ventilation, but did not abolish the ventilatory response to hypotension, indicating a response independent of peripheral chemoreceptors. Although there are previous data showing increased f H baroreflex sensitivity from 15 to 30°C in this species, further increases in temperature (35°C) diminished f H baroreflex gain (40.5±5.62 versus 21.6±4.64% kPa −1 ). Therefore, besides an involvement of pulmonary ventilation in matching O 2 delivery to demand at higher temperatures in anurans, it also plays a role in blood pressure regulation, independent of temperature, possibly owing to an interaction between baroreflex and respiratory areas in the brain, as previously suggested for mammals.

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Section: Temperature Effects On Cardiorespiratory Reflex Responsessupporting

confidence: 64%

Section: Temperature Effects On Cardiorespiratory Reflex Responsesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Zena

Silva

Gargaglioni

et al. 2016

Journal of Experimental Biology

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“…In contrast, the hypotensive tachycardia probably has more of an autoregulatory function, ensuring that perfusion pressure, and therefore tissue blood flow, is maintained to safeguard the tissues from ischaemia . Indeed, Hedrick et al (2015) argued that the main role of the baroreflex in three anuran amphibians is to restore arterial blood pressure following hypotensive events, because resting mean arterial pressure was only slightly lower than the saturation point for the respective baroreflex curves, making the f H in these animals much more responsive to hypotensive than to hypertensive events.…”

Section: Functional Significancementioning

confidence: 99%

Cardiac reflexes in a warming world: Thermal plasticity of barostatic control and autonomic tones in a temperate fish

Sandblom

Ekström

Brijs

et al. 2016

Journal of Experimental Biology

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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 rate of Biotest fish displayed clear thermal compensation and was 58.3±2.3 beats min −1 compared with 52.4±2.6 beats min −1 in reference fish at their respective environmental temperatures (Q 10 =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 tone, 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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“…The bullfrog Lithobates catesbeianus is an semiaquatic amphibian (Hedrick et al, 2015) native to the United States that was imported into Brazil in the early 1930s and has been raised in this country ever since (Rocha and Branco, 1998). This species has been used as a model for the study of SNT-induced neuropathic pain (Rigon et al, 2014(Rigon et al, , 2013Guedes et al, 2004a, b;Partata et al, 2002) because it provides a phylogenetic perspective on the mechanisms of pain research (Rigon et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Effect of Sciatic Nerve Transection on acetylcholinesterase activity in spinal cord and skeletal muscles of the bullfrog Lithobates catesbeianus

et al. 2017

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Sciatic nerve transection (SNT), a model for studying neuropathic pain, mimics the clinical symptoms of "phantom limb", a pain condition that arises in humans after amputation or transverse spinal lesions. In some vertebrate tissues, this condition decreases acetylcholinesterase (AChE) activity, the enzyme responsible for fast hydrolysis of released acetylcholine in cholinergic synapses. In spinal cord of frog Rana pipiens, this enzyme's activity was not significantly changed in the first days following ventral root transection, another model for studying neuropathic pain. An answerable question is whether SNT decreases AChE activity in spinal cord of frog Lithobates catesbeianus, a species that has been used as a model for studying SNT-induced neuropathic pain. Since each animal model has been created with a specific methodology, and the findings tend to vary widely with slight changes in the method used to induce pain, our study assessed AChE activity 3 and 10 days after complete SNT in lumbosacral spinal cord of adult male bullfrog Lithobates catesbeianus. Because there are time scale differences of motor endplate maturation in rat skeletal muscles, our study also measured the AChE activity in bullfrog tibial posticus (a postural muscle) and gastrocnemius (a typical skeletal muscle that is frequently used to study the motor system) muscles. AChE activity did not show significant changes 3 and 10 days following SNT in spinal cord. Also, no significant change occurred in AChE activity in tibial posticus and gastrocnemius muscles at day 3. However, a significant decrease was found at day 10, with reductions of 18% and 20% in tibial posticus and gastrocnemius, respectively. At present we cannot explain this change in AChE activity. While temporally different, the direction of the change was similar to that described for rats. This similarity indicates that bullfrog is a valid model for investigating AChE activity following SNT.Keywords: acetylcholinesterase, sciatic nerve transection, tibial posticus, gastrocnemius, spinal cord, frog. Efeito da Secção do Nervo Isquiático sobre a atividade da acetilcolinesterase em medula espinal e músculos esqueléticos da rã-touro Lithobates catesbeianus ResumoA transecção do nervo isquiático (SNT), um modelo para estudar dor neuropática, simula os sintomas clínicos do "membro fantasma", uma condição dolorosa que ocorre nos humanos após amputação ou secção completa da medula espinal. Essa condição muda a atividade da acetilcolinesterase (AChE), a enzima responsável pela rápida hidrólise da acetilcolina liberada nas sinapses colinérgicas, em alguns tecidos de vertebrados. Em medula espinal de rã Rana pipiens, a atividade da AChE não foi significativamente alterada nos primeiros dias após a secção da raiz ventral, outro modelo para o estudo da dor neuropática. Uma questão ainda não respondida é se a SNT diminui a atividade da AChE na medula espinal de rã Lithobates catesbeianus, uma espécie que vem sendo usada como modelo em estudos da dor neuropática induzida por SNT. Como...

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Baroreflex function in anurans from different environments

Cited by 15 publications

References 34 publications

Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Cardiac reflexes in a warming world: Thermal plasticity of barostatic control and autonomic tones in a temperate fish

Effect of Sciatic Nerve Transection on acetylcholinesterase activity in spinal cord and skeletal muscles of the bullfrog Lithobates catesbeianus

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