Cardiovascular responses to electrical stimulation of the recurrent laryngeal nerve in conscious toads (Bufo marinus)

Vliet, Bruce N. Van; West, Nigel H.

doi:10.1007/bf01101099

Cited by 22 publications

(27 citation statements)

References 19 publications

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“…Baroreceptor afferents also converge towards the nucleus of the solitary tract in R. schineideri (Bianchi-da-Silva et al, 2000), but any other synaptic transmission in the CNS of amphibians related to baroreflex control is still unknown. High intensity stimulation of the recurrent laryngeal nerve, which innervates the pulmocutaneous baroreceptors, elicits cardiovascular adjustments such as bradycardia and hypotension in addition to an increased apnea period in awake R. marina toads (Van Vliet and West, 1986). This observation corroborates the hypertension-induced reduction in ventilation we see in our toads.…”

Section: Blood Pressure Homeostasis In Anuran Amphibianssupporting

confidence: 80%

“…Besides cardiovascular responses, the baroreflex also influences respiratory function in mammals (for a review, see McMullan and Pilowsky, 2010). Although there are some suggestive data for baroreflex modulation of the respiratory system in crocodilians and amphibians (Van Vliet and West, 1986;Altimiras et al, 1998;Hedrick et al, 2013), there is still no direct evidence of a respiratory component in the reflex regulation of blood pressure in non-mammalian vertebrates.…”

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: Blood Pressure Homeostasis In Anuran Amphibianssupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Zena

Silva

Gargaglioni

et al. 2016

Journal of Experimental Biology

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“…Physiological doses of arginine vasotocin can increase lymph heart pressure without changing lymph heart rate (DeGrauw and Hillman, 2004). However, stimulation of the recurrent laryngeal nerve, which causes lymph hearts to stop beating (Crossley and Hillman, 1999), also causes apnea at high electrical stimulation intensities (Van Vliet and West, 1986). Further experiments are needed to clarify the role of blood pressure and blood volume status on lung ventilation in anurans.…”

Section: Discussionmentioning

confidence: 99%

Lung ventilation contributes to vertical lymph movement in anurans

Hedrick

Drewes

Hillman

et al. 2007

Journal of Experimental Biology

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SUMMARY Anurans (frogs and toads) generate lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very `leaky' vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located lymph hearts. At present, it is unclear how lymphatic fluid that accumulates in central body subcutaneous lymph sacs is moved to the anterior and posterior lymph hearts in the axillary regions and how lymph is moved, against gravity, to the dorsally located lymph hearts. In this study,we tested the hypothesis that lung ventilation, through its consequent effects on lymph sac pressure, contributes to the vertical movement of lymphatic fluid in the cane toad (Chaunus marinus) and the North American bullfrog(Lithobates catesbeiana). We measured pressure in the dorsal, lateral and subvertebral lymph sacs of anesthetized cane toads and bullfrogs during artificial lung inflation and deflation. We also measured pressure in the subvertebral lymph sac, which adheres to the dorsal surface of the lungs,simultaneously with brachial (forelimb) and pubic (posterior) sac pressure during ventilation in freely behaving animals. There were highly significant(P<0.001) relationships between lung pressure and lymph sac pressures (r2=0.19–0.72), indicating that pulmonary pressure is transmitted to the highly compliant lymph sacs that surround the lungs. Subvertebral sac pressure of resting animals was not significantly different between L. catesbeiana (518±282 Pa) and C. marinus (459±111 Pa). Brachial sac compliance (ml kPa–1 kg–1) also did not differ between the two species (33.6±5.0 in L. catesbeiana and 37.0±9.4 in C. marinus). During expiration (lung deflation), reductions in expanding subvertebral sac pressure are communicated to the brachial lymph sac. Changes in brachial and pubic lymph sac pressures were correlated almost entirely during expiration rather than inspiration. The change in brachial sac pressure during expiration was 235±43 Pa for C. marinus and 215±50 Pa for L. catesbeiana, which is of sufficient magnitude to move lymph the estimated 0.5–1.0 cm vertical distance from the forelimb to the vicinity of the anterior lymph hearts. We suggest that lymph is moved during expiration to the subvertebral sac from anterior and posterior lymph sacs. During lung inflation, increased lymph sac pressure moves lymph to axillary regions, where lymph hearts can return lymph to the vascular space. Consequently, pulmonary ventilation has an important role for lymph movement and, hence, blood volume regulation in anurans.

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“…Electrical stimulation of the recurrent laryngeal nerve also produces a reduction in aortic and an increase in p.c.a. vascular resistances (Van Vliet & West, 1986). It has been suggested that the p.c.a.…”

Section: Introductionmentioning

confidence: 99%

“…It has been suggested that the p.c.a. baroreflex may be important in protecting the lung from elevated arterial pressures (West & Van Vliet, 1983;Bagshaw, 1985; Smits, West & Burggren, 1986;Van Vliet & West, 1986).…”

Section: Introductionmentioning

confidence: 99%

Responses to circulatory pressures, and conduction velocity, of pulmocutaneous baroreceptors in Bufo marinus.

Vliet

West

1987

The Journal of Physiology

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SUMMARY1. Baroreceptor activity was recorded within the recurrent laryngeal branch of the toad vagus in forty-four preparations. The receptive fields of the receptors were located in the pulmocutaneous artery (p.c.a.), generally within 5 mm of its separation from the truncus. However, the most easily recorded afferents in this nerve were mechanoreceptors which responded to punctate stimulation of the lip of the glottis.2. The conduction velocities of p.c.a. baroreceptor and mechanoreceptive glottal afferents recorded in the recurrent laryngeal nerve ranged from 0 3-07 (0-5+041) m s-1 and 2-2-14-0 (6 8+0 8) m s-1 respectively, which suggests that baroreceptor afferent fibres are non-myelinated and that glottal afferent fibres are myelinated.3. The p.c.a. baroreceptor discharge was largely confined to a period of systole in which systemic and p.c.a. arterial pressure profiles were identical. The maximum discharge frequency, number of spikes per cycle, and the duration of discharge increased, and the discharge latency decreased, as p.c.a. pressures were elevated. The latency of the discharge was pronounced at low p.c.a. pressures, and could be partially accounted for by the conduction time of the baroreceptor afferents to the electrodes (up to 100 ms).4. Carotid and aortic arterial baroreceptor and pharyngeal afferents were recorded in two pharyngeal branches of the vagus nerve which were closely associated with the carotid and aortic arterial arches.5. It is suggested that baroreceptor populations with their receptive fields in the third-(carotid) and sixth-(p.c.a. or pulmonary) arch arteries should be considered homologous in anurans and mammals, but that those of the fourth-(aorta) arch artery should not, since the vagal branches in which their afferents are carried do not appear to be equivalent in anurans and mammals.

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Cardiovascular responses to electrical stimulation of the recurrent laryngeal nerve in conscious toads (Bufo marinus)

Cited by 22 publications

References 19 publications

Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Baroreflex regulation affects ventilation in the Cururu toad Rhinella schneideri

Lung ventilation contributes to vertical lymph movement in anurans

Responses to circulatory pressures, and conduction velocity, of pulmocutaneous baroreceptors in Bufo marinus.

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