Effect of the dry-cold season dormancy on the tonic and phasic neural control of heart rate in the toad,Bufo paracnemis

Hoffmann, Anette; Romero, Sônia Maria Brazil

doi:10.1002/1097-010x(20000615)287:1<15::aid-jez2>3.0.co;2-e

Cited by 4 publications

(3 citation statements)

References 24 publications

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“…Some particularities do exist, such as no reflex hypotension induced by baroreceptors in Xenopus (2) and an absence of drug-induced autonomous tonus changes in Lithobates catesbeianus (3). At the same time, studies have shown that the heart of Rhinella schneideri is innervated by both sympathetic and parasympathetic systems (4). R. marina presents sympathetic tachycardia (5).…”

Section: Introductionmentioning

confidence: 99%

Analysis of heart rate control to assess thermal sensitivity responses in Brazilian toads

Natali¹,

Santos²,

Rodrigues³

et al. 2015

Braz J Med Biol Res

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In anurans, changes in ambient temperature influence body temperature and, therefore, energy consumption. These changes ultimately affect energy supply and, consequently, heart rate (HR). Typically, anurans living in different thermal environments have different thermal sensitivities, and these cannot be distinguished by changes in HR. We hypothesized that Rhinella jimi (a toad from a xeric environment that lives in a wide range of temperatures) would have a lower thermal sensitivity regarding cardiac control than R. icterica (originally from a tropical forest environment with a more restricted range of ambient temperatures). Thermal sensitivity was assessed by comparing animals housed at 15° and 25°C. Cardiac control was estimated by heart rate variability (HRV) and heart rate complexity (HRC). Differences in HRV between the two temperatures were not significant (P=0.214 for R. icterica and P=0.328 for R. jimi), whereas HRC differences were. All specimens but one R. jimi had a lower HRC at 15°C (all P<0.01). These results indicate that R. jimi has a lower thermal sensitivity and that cardiac control is not completely dependent on the thermal environment because HRC was not consistently different between temperatures in all R. jimi specimens. This result indicates a lack of evolutive trade-offs among temperatures given that heart rate control at 25°C is potentially not a constraint to heart rate control at 15°C.

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Section: Introductionmentioning

confidence: 99%

Analysis of heart rate control to assess thermal sensitivity responses in Brazilian toads

Natali¹,

Santos²,

Rodrigues³

et al. 2015

Braz J Med Biol Res

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“…(Axelsson et al, 1987;Morris and Nilsson, 1994). The autonomic fibres controlling the heart are continuously active, thereby creating a nervous tone which increases the efficacy of the heart rate response (Altimiras et al, 1997;Hoffman and Romero, 2000). There is evidence that changes in the cholinergic tone on the heart are the principle mechanism controlling heart rate during exercise in fish (Axelsson et al, 1987;Altimiras et al, 1997).…”

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confidence: 99%

“…Moreover, there are species-specific differences in the relative importance of cholinergic and adrenergic autonomic control of the heart. For example, the heart of the toad Bufo paracnemis at rest was under the influence of both cholinergic and adrenergic tone (Hoffman and Romero, 2000), whereas heart rate in resting Bufo marinus was regulated by cholinergic fibres alone, but tachycardia during exercise in this species was effected by adrenergic fibres (Wahlqvist and Campbell, 1988).…”

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confidence: 99%

Control of heart rate during thermoregulation in the heliothermic lizard Pogona barbata: importance of cholinergic and adrenergic mechanisms

Seebacher

Franklin

2001

Journal of Experimental Biology

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SUMMARY During thermoregulation in the bearded dragon Pogona barbata, heart rate when heating is significantly faster than when cooling at any given body temperature (heart rate hysteresis), resulting in faster rates of heating than cooling. However, the mechanisms that control heart rate during heating and cooling are unknown. The aim of this study was to test the hypothesis that changes in cholinergic and adrenergic tone on the heart are responsible for the heart rate hysteresis during heating and cooling in P. barbata. Heating and cooling trials were conducted before and after the administration of atropine, a muscarinic antagonist, and sotalol, a β-adrenergic antagonist. Cholinergic and β-adrenergic blockade did not abolish the heart rate hysteresis, as the heart rate during heating was significantly faster than during cooling in all cases. Adrenergic tone was extremely high (92.3 %) at the commencement of heating, and decreased to 30.7 % at the end of the cooling period. Moreover, in four lizards there was an instantaneous drop in heart rate (up to 15 beats min–1) as the heat source was switched off, and this drop in heart rate coincided with either a drop in β-adrenergic tone or an increase in cholinergic tone. Rates of heating were significantly faster during the cholinergic blockade, and least with a combined cholinergic and β-adrenergic blockade. The results showed that cholinergic and β-adrenergic systems are not the only control mechanisms acting on the heart during heating and cooling, but they do have a significant effect on heart rate and on rates of heating and cooling.

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Role of brain nitric oxide in the cardiovascular control of bullfrogs

Zena

Gargaglioni

Bícego

2013

Comparative Biochemistry and Physiology Part A: Molecular &

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The goal of the present study was to determine if nitric oxide (NO) acting on the brain of bullfrog (Lithobates catesbeianus) is involved in arterial pressure and heart rate (HR) control by influencing sympathetic activity. We investigated the effect of intracerebroventricular injections of L-NMMA (a nonselective NO synthase inhibitor) on mean arterial blood pressure (MAP), HR and cutaneous vascular conductance (CVC) of pelvic skin after intravenous injection of α or β adrenergic blockers, prazosin or sotalol, respectively. Arterial pressure was directly measured by a telemetry sensor inserted in the aortic arch of animals. L-NMMA increased MAP, but did not change HR. This hypertensive response was inhibited by the pre-treatment with prazosin, but accentuated by sotalol. The effect of L-NMMA on MAP was also inhibited by i.v. injections of the ganglionic blocker, hexamethonium. Thus, NO acting on the brain of bullfrog seems to present a hypotensive effect influencing the sympathetic activity dependent on α and β adrenergic receptors in the periphery.

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Effect of the dry-cold season dormancy on the tonic and phasic neural control of heart rate in the toad,Bufo paracnemis

Cited by 4 publications

References 24 publications

Analysis of heart rate control to assess thermal sensitivity responses in Brazilian toads

Analysis of heart rate control to assess thermal sensitivity responses in Brazilian toads

Control of heart rate during thermoregulation in the heliothermic lizard Pogona barbata: importance of cholinergic and adrenergic mechanisms

Role of brain nitric oxide in the cardiovascular control of bullfrogs

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