Central Chemosensitivity in Mammals

Hartzler, Lynn K.; Putnam, Robert W.

doi:10.1007/978-3-540-93985-6_19

Cited by 2 publications

(1 citation statement)

References 136 publications

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“…The negative feedback system that drives ventilation has been mainly elucidated in mammals that tightly regulate arterial pH. Specifically, chemosensory structures are well defined and the cellular mechanisms underlying chemosensitivity have been extensively studied in mammals (Guyenet and Bayliss, 2015;Hartzler and Putnam, 2009;Huckstepp and Dale, 2011), where the CO 2 /pH-sensitive brainstem areas involved in respiratory chemosensing are located in regions surrounding the fourth ventricle (Coates et al, 1993;Huckstepp and Dale, 2011).…”

Section: Introductionmentioning

confidence: 99%

Effect of temperature on chemosensitive locus coeruleus neurons of Savannah monitor lizardsVaranus exanthematicus

Zena

Fonseca

Santin

et al. 2016

Journal of Experimental Biology

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Savannah monitor lizards (Varanus exanthematicus) are unusual among ectothermic vertebrates in maintaining arterial pH nearly constant during changes in body temperature in contrast to the typical α-stat regulating strategy of most other ectotherms. Given the importance of pH in the control of ventilation, we examined the CO 2 /H + sensitivity of neurons from the locus coeruleus (LC) region of monitor lizard brainstems. Whole-cell patch-clamp electrophysiology was used to record membrane voltage in LC neurons in brainstem slices. Artificial cerebral spinal fluid equilibrated with 80% O 2 , 0.0-10.0% CO 2 , balance N 2 , was superfused across brainstem slices. Changes in firing rate of LC neurons were calculated from action potential recordings to quantify the chemosensitive response to hypercapnic acidosis. Our results demonstrate that the LC brainstem region contains neurons that can be excited or inhibited by, and/or are not sensitive to CO 2 in V. exanthematicus. While few LC neurons were activated by hypercapnic acidosis (15%), a higher proportion of the LC neurons responded by decreasing their firing rate during exposure to high CO 2 at 20°C (37%); this chemosensitive response was no longer exhibited when the temperature was increased to 30°C. Further, the proportion of chemosensitive LC neurons changed at 35°C with a reduction in CO 2 -inhibited (11%) neurons and an increase in CO 2 -activated (35%) neurons. Expressing a high proportion of inhibited neurons at low temperature may provide insights into mechanisms underlying the temperature-dependent pH-stat regulatory strategy of savannah monitor lizards.

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Section: Introductionmentioning

confidence: 99%

Effect of temperature on chemosensitive locus coeruleus neurons of Savannah monitor lizardsVaranus exanthematicus

Zena

Fonseca

Santin

et al. 2016

Journal of Experimental Biology

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Lactate provides a strong pH-independent ventilatory signal in the facultative air-breathing teleost Pangasianodon hypophthalmus

Thomsen

Wang

Milsom

et al. 2017

Sci Rep

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Fish regulate ventilation primarily by sensing O2-levels in the water and arterial blood. It is well established that this sensory process involves several steps, but the underlying mechanisms remain frustratingly elusive. Here we examine the effect of increasing lactate ions at constant pH on ventilation in a teleost; specifically the facultative air-breathing catfish Pangasianodon hypophthalmus. At lactate levels within the physiological range obtained by Na-Lactate injections (3.5 ± 0.8 to 10.9 ± 0.7 mmol L−1), gill ventilation increased in a dose-dependent manner to levels comparable to those elicited by NaCN injections (2.0 µmol kg−1), which induces a hypoxic response and higher than those observed in any level of ambient hypoxia (lowest PO2 = 20 mmHg). High lactate concentrations also stimulated air-breathing. Denervation of the first gill arch reduced the ventilatory response to lactate suggesting that part of the sensory mechanism for lactate is located at the first gill arch. However, since a residual response remained after this denervation, the other gill arches or extrabranchial locations must also be important for lactate sensing. We propose that lactate plays a role as a signalling molecule in the hypoxic ventilatory response in fish.

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Central Chemosensitivity in Mammals

Cited by 2 publications

References 136 publications

Effect of temperature on chemosensitive locus coeruleus neurons of Savannah monitor lizardsVaranus exanthematicus

Effect of temperature on chemosensitive locus coeruleus neurons of Savannah monitor lizardsVaranus exanthematicus

Lactate provides a strong pH-independent ventilatory signal in the facultative air-breathing teleost Pangasianodon hypophthalmus

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