The influence of descending inputs on breathing pattern formation in the isolated bullfrog brainstem-spinal cord

Reid, Scott D.; Meier, Janice T.; Milsom, William K.

doi:10.1016/s0034-5687(99)00117-6

Cited by 27 publications

(21 citation statements)

References 24 publications

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“…Toads were anaesthetised by emersion in a solution of 3-aminobenzoic acid ethyl ester (MS222, 1.0·g·l -1 ; Sigma) buffered to pH·7.0 with sodium bicarbonate (Reid and Milsom, 1998;Reid et al, 2000a;Reid et al, 2000b;Gheshmy et al, 2006). Animals were kept in the anaesthetic until the eye-blink and toe-pinch reflexes were eliminated.…”

Section: Olfactory Denervationmentioning

confidence: 99%

Afferent input modulates the chronic hypercapnia-induced increase in respiratory-related central pH/CO2 chemosensitivity in the cane toad (Bufo marinus)

Gheshmy

Anari

Besada

et al. 2007

Journal of Experimental Biology

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pH increased fictive breathing in preparations taken from control and CHC animals. CHC caused an increase in fictive breathing compared with controls. OD and CHH abolished the CHC-induced augmentation of fictive breathing. In vivo, CHC did not cause an augmentation of the acute hypercapnic ventilatory response. CHH reduced the in vivo acute hypercapnic ventilatory response compared with animals exposed to CHC. In vivo, OD reduced breathing frequency and increased breath amplitude in both control and CHC animals. The results suggest that afferent input from olfactory and arterial chemoreceptors, during CHC, is involved in triggering the CHC-induced increase in central respiratory-related pH/CO 2 chemosensitivity.

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Section: Olfactory Denervationmentioning

confidence: 99%

Afferent input modulates the chronic hypercapnia-induced increase in respiratory-related central pH/CO2 chemosensitivity in the cane toad (Bufo marinus)

Gheshmy

Anari

Besada

et al. 2007

Journal of Experimental Biology

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“…In the intact animal, a branch of the vagus nerve innervates the glottis, which opens and closes with each breath. Since these preparations are devoid of any afferent input and breathing is an inherently rhythmic process generated in the brainstem, all rhythmic activity (in vitro motor output) recorded from the vagus nerve was assumed to represent motor output to the respiratory muscles (glottis) and is therefore an index of breathing termed fictive breathing (Sakakibara, 1984a;Sakakibara, 1984b;Kinkead et al, 1994;McLean et al, 1995;Reid and Milsom, 1998;Reid et al, 2000a;Reid et al, 2000b;Morales and Hedrick, 2002;Taylor et al, 2003a;Taylor et al, 2003b).…”

Section: In Vitro Experiments the In Vitro Brainstem-spinal Cord Prepmentioning

confidence: 99%

“…Following the 1·h stabilisation period, the pH of the aCSF was increased to 8.0 and then lowered to 7.8 and 7.5 in 30·min intervals. Following this, the brain was transected slightly caudal to the optic chiasma at a level previously demonstrated to significantly attenuate (and almost abolish) episodic (clustered) fictive breathing (Reid et al, 2000a) as well as alter the pH sensitivity of fictive breathing in brains taken from chronically hypoxic toads (J. McAneney and S. Reid, unpublished data). Following a second 1·h stabilisation period, the pH changes (8.0, 7.8 and 7.5) were repeated.…”

Section: Series 2: Effects Of Chc and Midbrain Transection On Phsensimentioning

confidence: 99%

“…Reid et al (Reid et al, 2000a) demonstrated, using in vitro brainstem-spinal cord preparations from the bullfrog, that a transection slightly caudal to the optic chiasma converted episodic fictive breathing to continuous fictive breathing with a concomitant increase in fictive breathing frequency. A recent study from this laboratory (J. McAneney and S. Reid, unpublished) demonstrated that, in cane toads, 10·days of exposure to chronic normobaric hypoxia (10% O 2 ) tended to cause a decrease in central pH/CO 2 chemosensitivity measured using the in vitro brainstem-spinal cord preparation.…”

Section: Chronic Hypercapnia Increases Centralmentioning

confidence: 99%

“…Cane toads (Bufo marinus; a species in which respiratory physiology has been well studied) were exposed to CHC for 9 days, following which central pH/CO 2 chemosensitivity was assessed using in vitro brainstem-spinal cord preparations and whole animal hypercapnic ventilatory responses were measured in vivo. A midbrain transection slightly caudal to the optic chiasma was previously demonstrated to reduce the clustering of breaths into episodes and cause an increase in fictive breathing frequency in vitro (Reid et al, 2000a). We hypothesised that a change in descending inputs, from the level of the optic chiasma, would alter CO 2 chemosensitivity following CHC.…”

Section: Introductionmentioning

confidence: 96%

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Chronic hypercapnia modulates respiratory-related central pH/CO2 chemoreception in an amphibian,Bufo marinus

Gheshmy

Vukelich

Noronha

et al. 2006

Journal of Experimental Biology

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SUMMARY Anuran amphibians have multiple populations of pH/CO2-sensitive respiratory-related chemoreceptors. This study examined in cane toads(Bufo marinus) whether chronic hypercapnia (CHC) altered the pH/CO2 sensitivity of central respiratory-related chemoreceptors in vitro and whether CHC altered the acute hypercapnic ventilatory response (HCVR; 5% CO2) in vivo. Toads were exposed to CHC(3.5% CO2) for 9 days. In vitro brainstem–spinal cord preparations were used to examine central respiratory-related pH/CO2 chemosensitivity. CHC augmented in vitro fictive breathing as the pH of the superfusate was lowered from 8.2 to 7.4. Midbrain transection in vitro (at a level known to reduce the clustering of breaths) did not alter this augmentation. In vivo, CHC did not alter the acute HCVR but midbrain transection changed the breathing pattern and increased the overall level of ventilation. CHC did not alter the effect of olfactory CO2 chemoreceptor denervation on the acute HCVR in vivo but did alter the response when returned to normal air. The results indicate that CHC increases the response of central pH/CO2chemoreceptors to changes in cerebrospinal fluid pH in vitro yet this increase is not manifest as an increase in the HCVR in vivo.

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Hibernation and Gas Exchange

Milsom

Jackson

2011

Comprehensive Physiology

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Hibernation in endotherms and ectotherms is characterized by an energy-conserving metabolic depression due to low body temperatures and poorly understood temperature-independent mechanisms. Rates of gas exchange are correspondly reduced. In hibernating mammals, ventilation falls even more than metabolic rate leading to a relative respiratory acidosis that may contribute to metabolic depression. Breathing in some mammals becomes episodic and in some small mammals significant apneic gas exchange may occur by passive diffusion via airways or skin. In ectothermic vertebrates, extrapulmonary gas exchange predominates and in reptiles and amphibians hibernating underwater accounts for all gas exchange. In aerated water diffusive exchange permits amphibians and many species of turtles to remain fully aerobic, but hypoxic conditions can challenge many of these animals. Oxygen uptake into blood in both endotherms and ectotherms is enhanced by increased affinity of hemoglobin for O₂ at low temperature. Regulation of gas exchange in hibernating mammals is predominately linked to CO₂/pH, and in episodic breathers, control is principally directed at the duration of the apneic period. Control in submerged hibernating ectotherms is poorly understood, although skin-diffusing capacity may increase under hypoxic conditions. In aerated water blood pH of frogs and turtles either adheres to alphastat regulation (pH ∼8.0) or may even exhibit respiratory alkalosis. Arousal in hibernating mammals leads to restoration of euthermic temperature, metabolic rate, and gas exchange and occurs periodically even as ambient temperatures remain low, whereas body temperature, metabolic rate, and gas exchange of hibernating ectotherms are tightly linked to ambient temperature.

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The influence of descending inputs on breathing pattern formation in the isolated bullfrog brainstem-spinal cord

Cited by 27 publications

References 24 publications

Afferent input modulates the chronic hypercapnia-induced increase in respiratory-related central pH/CO2 chemosensitivity in the cane toad (Bufo marinus)

Afferent input modulates the chronic hypercapnia-induced increase in respiratory-related central pH/CO2 chemosensitivity in the cane toad (Bufo marinus)

Chronic hypercapnia modulates respiratory-related central pH/CO2 chemoreception in an amphibian,Bufo marinus

Hibernation and Gas Exchange

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