Ontogeny of central chemoreception during fictive gill and lung ventilation in an in vitro brainstem preparation of Rana catesbeiana

1997 ◽  
Vol 200 (15) ◽  
pp. 2063-2072 ◽  
Author(s):  
C Torgerson ◽  
M Gdovin ◽  
J Remmers
Keyword(s):  
Rana Catesbeiana ◽  
Cranial Nerves ◽  
Lung Ventilation ◽  
Artificial Cerebrospinal Fluid ◽  
Gill Ventilation ◽  
Central Chemoreception ◽  
Bullfrog Tadpole ◽  
Spontaneously Breathing ◽  
Hypercapnic Response

An isolated brainstem preparation of the bullfrog tadpole, Rana catesbeiana, displays coordinated rhythmic bursting activities in cranial nerves V, VII and X in vitro. In decerebrate, spontaneously breathing tadpoles, we have previously shown that these bursts correspond to fluctuations in buccal and lung pressures and to bursts of activity in the buccal levator muscle H3a. This demonstrates that the rhythmic bursting activities recorded in vitro represent fictive gill and lung ventilation. To investigate the ontogeny of central respiratory chemoreception during the transition from gill to lung ventilation, we superfused the isolated brainstems of four larval stage groups with oxygenated artificial cerebrospinal fluid at various levels of PCO2. We measured shifts in the pattern of fictive respiratory output and the response to central hypercapnic stimulation throughout development. At normal PCO2 (2.3 kPa), stage 3­9 tadpoles displayed rhythmic neural bursts associated with gill ventilation, while stages 10­14 and 15­19 tadpoles produced oscillating bursting activity associated with both gill and lung respiration, and tadpoles at stages 20­25 displayed neural activity predominantly associated with lung ventilation. In stage 3­9 tadpoles, variations in PCO2 of the superfusate (0.5­6.0 kPa) caused almost no change in fictive gill or lung ventilation. By contrast, stage 10­14 tadpoles showed a significant hypercapnic response (P<0.05) in the amplitude and frequency of fictive gill ventilation, which was accompanied by a significant increase (P<0.05) in the burst amplitude and respiratory output of cranial nerve X over that occurring at all other stages. The amplitude and frequency of fictive gill ventilation in stages 15­19 increased significantly (P<0.05) in response to pH reduction, but became insensitive to hypercapnia at stages 20­25. The frequency of fictive lung ventilation was unresponsive to hypercapnia in stage 10­14, increased significantly by stage 15­19 (P<0.05) and became maximal (P<0.05) in stages 20­25. Overall, we describe the ontological development of central respiratory chemoreceptors driving respiratory output in the larval amphibian, demonstrating transfer in central chemoreceptive influence from gill to lung regulation during metamorphic stages. In addition, we provide novel evidence for the stimulatory influence of central chemoreceptors on fictive gill ventilation in response to CO2.

Fictive Gill and Lung Ventilation in the Pre- and Postmetamorphic Tadpole Brain Stem

1998 ◽  
Vol 80 (4) ◽  
pp. 2015-2022 ◽  
Author(s):  
C. S. Torgerson ◽  
M. J. Gdovin ◽  
J. E. Remmers
Keyword(s):  
Brain Stem ◽  
Rana Catesbeiana ◽  
Low Frequency ◽  
Lung Ventilation ◽  
High Amplitude ◽  
Spinal Nerve ◽  
Gill Ventilation ◽  
Respiratory Behavior ◽  
Spontaneously Breathing

Torgerson, C. S., M. J. Gdovin, and J. E. Remmers. Fictive gill and lung ventilation in the pre- and postmetamorphic tadpole brain stem. J. Neurophysiol. 80: 2015–2022, 1998. The pattern of efferent neural activity recorded from the isolated brain stem preparation of the tadpole Rana catesbeiana was examined to characterize fictive gill and lung ventilations during ontogeny. In vitro recordings from cranial nerve (CN) roots V, VII, and X and spinal nerve (SN) root II of premetamorphic tadpoles showed a coordinated sequence of rhythmic bursts occurring in one of two patterns, pattern1, high-frequency, low-amplitude bursts lacking corresponding activity in SN II and pattern 2, low-frequency, high-amplitude bursts with coincident bursts in SN II. These two patterns corresponded to gill and lung ventilatory burst patterns, respectively, recorded from nerve roots of decerebrate, spontaneously breathing tadpoles. Similar patterns were observed in brain stem preparations from postmetamorphic tadpoles except that they showed a greater frequency of lung bursts and they expressed fictive gill ventilation in SN II. The laryngeal branch of the vagus (Xl) displayed efferent bursts in phase with gill and lung activity, suggesting fictive glottal constriction during gill ventilation and glottal dilation during lung ventilation. The fictive gill ventilatory cycle of pre- and postmetamorphic tadpoles was characterized by a rostral to caudal sequence of CN bursts. The fictive lung ventilatory pattern in the premetamorphic animal was initiated by augmenting CN VII discharge followed by synchronous bursts in CN V, X, SN II, and Xl. By contrast, postmetamorphic patterns of fictive lung ventilation were characterized by lung burst activity in SN II that preceded burst onset in CN V and followed the lead burst in CN VII. We conclude that recruitment and timing of pattern 1 and pattern 2 rhythmic bursts recorded in vitro closely resemble that recorded during spontaneous respiratory behavior, indicating that the two patterns are the neural equivalent of gill and lung ventilation, respectively. Further, fictive gill and lung ventilatory patterns in postmetamorphic tadpoles differ in burst onset latency from premetamorphic tadpole patterns and resemble fictive oropharyngeal and pulmonary burst cycles in adult frogs.

Ontogeny of central CO2 chemoreception: chemosensitivity in the ventral medulla of developing bullfrogs

2003 ◽  
Vol 285 (6) ◽  
pp. R1461-R1472 ◽  
Author(s):  
Barbara E. Taylor ◽  
Michael B. Harris ◽  
J. C. Leiter ◽  
Matthew J. Gdovin
Keyword(s):  
Cerebrospinal Fluid ◽  
Kainic Acid ◽  
Rana Catesbeiana ◽  
Lung Ventilation ◽  
Ventral Surface ◽  
Spinal Nerve ◽  
Ventral Medulla ◽  
Unilateral Stimulation ◽  
Artificial Cerebrospinal Fluid ◽  
Hypercapnic Response

Sites of central CO2 chemosensitivity were investigated in isolated brain stems from Rana catesbeiana tadpoles and frogs. Respiratory neurograms were made from cranial nerve (CN) 7 and spinal nerve 2. Superfusion of the brain stem with hypercapnic artificial cerebrospinal fluid elicited increased fictive lung ventilation. The effect of focal perfusion of hypercapnic artificial cerebrospinal fluid on discrete areas of the ventral medulla was assessed. Sites of chemosensitivity, which are active continuously throughout development, were identified adjacent to CN 5 and CN 10 on the ventral surface of the medulla. In early- and middle-stage tadpoles and frogs, unilateral stimulation within either site was sufficient to elicit the hypercapnic response, but simultaneous stimulation within both sites was required in late-stage tadpoles. The chemosensitive sites were individually disrupted by unilateral application of 1 mg/ml protease, and the sensitivity to bath application or focal perfusion of hypercapnia was reassessed. Protease lesions at CN 10 abolished the entire hypercapnic response, but lesions at CN 5 affected only the hypercapnic response originating from the CN 5 site. Neurons within the chemosensitive sites were also destroyed by unilateral application of 1 mM kainic acid, and the sensitivity to bath or focal application of hypercapnia was reassessed. Kainic acid lesions within either site abolished the hypercapnic response. Using a vital dye, we determined that kainic acid destroyed neurons by only within 100 μm of the ventral medullary surface. Thus, regardless of developmental stage, neurons necessary for CO2 sensitivity are located in the ventral medulla adjacent to CN 5 and 10.

Location of central respiratory chemoreceptors in the developing tadpole

2001 ◽  
Vol 280 (4) ◽  
pp. R921-R928 ◽  
Author(s):  
C. S. Torgerson ◽  
M. J. Gdovin ◽  
R. Brandt ◽  
J. E. Remmers
Keyword(s):  
Cerebrospinal Fluid ◽  
Brain Stem ◽  
Rana Catesbeiana ◽  
Lung Ventilation ◽  
Maximum Reduction ◽  
Amphibian Larvae ◽  
Artificial Cerebrospinal Fluid ◽  
Premetamorphic Tadpole

The location of central respiratory chemoreceptors in amphibian larvae may change as the central chemoreceptive function shifts from driving gill to driving lung ventilation during metamorphosis. We examined this possibility in the in vitro brain stem of the pre- and postmetamorphic Rana catesbeiana tadpole by microinjecting hypercapnic artificial cerebrospinal fluid (aCSF) while recording fictive lung ventilation. The rostral and caudal brain stem were separately explored systematically using injections of 11 nl of aCSF equilibrated with 100% CO2 that transiently acidified a 500-μm region, producing a maximum reduction in pH of 0.23 ± 0.06 at the site of injection. In postmetamorphic tadpoles, chemoreceptive sites were concentrated in the rostral compared with the caudal brain stem. No such segregation was observed in the premetamorphic tadpole. We conclude that, as in lung rhythmogenic function, respiratory chemosensitivity emerges rostrally in the amphibian brain stem during development.

Central CO2 chemoreception in developing bullfrogs: anomalous response to acetazolamide

2003 ◽  
Vol 94 (3) ◽  
pp. 1204-1212 ◽  
Author(s):  
Barbara E. Taylor ◽  
Michael B. Harris ◽  
E. Lee Coates ◽  
Matthew J. Gdovin ◽  
J. C. Leiter
Keyword(s):  
Carbonic Anhydrase ◽  
Late Stage ◽  
Rana Catesbeiana ◽  
Early Stage ◽  
Lung Ventilation ◽  
Carbonic Anhydrase Activity ◽  
Spinal Nerve ◽  
Before And After ◽  
Hypercapnic Response

Central CO2 chemoreception and the role of carbonic anhydrase were assessed in brain stems from Rana catesbeiana tadpoles and frogs. Buccal and lung rhythms were recorded from cranial nerve VII and spinal nerve II during normocapnia and hypercapnia before and after treatment with 25 μM acetazolamide. The lung response to acetazolamide mimicked the hypercapnic response in early-stage and midstage metamorphic tadpoles and frogs. In late-stage tadpoles, acetazolamide actually inhibited hypercapnic responses. Acetazolamide and hypercapnia decreased the buccal frequency but had no effect on the buccal duty cycle. Carbonic anhydrase activity was present in the brain stem in every developmental stage. Thus more frequent lung ventilation and concomitantly less frequent buccal ventilation comprised the hypercapnic response, but the response to acetazolamide was not consistent during metamorphosis. Therefore, acetazolamide is not a useful tool for central CO2 chemoreceptor studies in this species. The reversal of the effect of acetazolamide in late-stage metamorphosis may reflect reorganization of central chemosensory processes during the final transition from aquatic to aerial respiration.

Excitatory and inhibitory effects of tricaine (MS-222) on fictive breathing in isolated bullfrog brain stem

2003 ◽  
Vol 284 (2) ◽  
pp. R405-R412 ◽  
Author(s):  
Michael S. Hedrick ◽  
Rachel E. Winmill
Keyword(s):  
Brain Stem ◽  
Rana Catesbeiana ◽  
Motor Output ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Artificial Cerebrospinal Fluid ◽  
Channel Blocking ◽  
The Central Nervous System ◽  
Excitatory Neurotransmission

This study examined the direct effects of tricaine methanesulfonate (MS-222), a sodium-channel blocking local anesthetic, on respiratory motor output using an in vitro brain stem preparation of adult North American bullfrogs ( Rana catesbeiana). Bullfrogs were anesthetized with halothane, and the brain stem was removed and superfused with artificial cerebrospinal fluid containing MS-222 at concentrations ranging from 0.1 to 1,000 μM. At the lowest concentration of MS-222, respiratory frequency ( f R) increased significantly ( P < 0.05), but at higher concentrations, f R progressively decreased and was abolished in all preparations at 1,000 μM ( P < 0.01). Respiratory burst amplitude and burst duration were not affected by MS-222. The frequency of nonrespiratory neural activity did not significantly change with the addition of MS-222 below 1,000 μM. These data indicate that MS-222 has a significant, direct effect on respiratory motor output from the central nervous system, producing both excitation and inhibition of fictive breathing. The results are consistent with other studies demonstrating that low concentrations of anesthetics generally cause excitation followed by depression at higher concentrations. Although the mechanisms underlying the excitatory effects of MS-222 in this study are unclear, they may include increased excitatory neurotransmission and/or disinhibition of inputs to the respiratory central pattern generator.

Sites of respiratory rhythmogenesis during development in the tadpole

2001 ◽  
Vol 280 (4) ◽  
pp. R913-R920 ◽  
Author(s):  
C. S. Torgerson ◽  
M. J. Gdovin ◽  
J. E. Remmers
Keyword(s):  
Brain Stem ◽  
Rana Catesbeiana ◽  
Lung Ventilation ◽  
Respiratory Rhythmogenesis ◽  
Amphibian Larvae ◽  
Before And After ◽  
Lung Ventilator ◽  
Necessary And Sufficient ◽  
Stem Segments

During ontogeny, amphibian larvae experience a dramatic alteration in the motor act of breathing as the premetamorphic gill breather develops into the postmetamorphic lung ventilator. We tested the hypothesis that the site of lung rhythmogenesis relocates during metamorphosis by recording fictive lung ventilation before and after transecting the in vitro brain stem of pre- and postmetamorphic Rana catesbeiana into four segments. In premetamorphic tadpoles, the two caudalmost brain stem segments combined proved to be the minimum brain stem configuration necessary and sufficient for lung burst generation. In the postmetamorphic counterpart, this function was supplied by the combination of the two rostralmost brain stem segments. In the postmetamorphic brain stem, a 500-μm segment lying just rostral to cranial nerve IX conveys rhythmogenic capability to neighboring rostral or caudal segments. We conclude that lung rhythmogenic capability translocates rostrally during development as the tadpole shifts from gill to lung ventilation.

Regulation of the respiratory central pattern generator by chloride-dependent inhibition during development in the bullfrog (Rana catesbeiana)

2002 ◽  
Vol 205 (8) ◽  
pp. 1161-1169 ◽  
Author(s):  
Lise Broch ◽  
Rey D. Morales ◽  
Anthony V. Sandoval ◽  
Michael S. Hedrick
Keyword(s):  
Receptor Antagonist ◽  
Central Pattern Generator ◽  
Rana Catesbeiana ◽  
Lung Ventilation ◽  
Pattern Generator ◽  
Burst Frequency ◽  
Inhibitory Mechanisms ◽  
Burst Amplitude ◽  
Gill Ventilation ◽  
Respiratory Central Pattern Generator

SUMMARYIsolated brainstem preparations from larval (tadpole) and adult Rana catesbeiana were used to examine inhibitory mechanisms for developmental regulation of the respiratory central pattern generator (CPG). Preparations were superfused at 20-22 °C with Cl--free artificial cerebrospinal fluid (aCSF) or with aCSF containing agonists/antagonists ofγ-aminobutyric acid (GABA) or glycine receptors. Respiratory motor output from the CPG, measured as neural activity from cranial nerve roots, was associated with fictive gill ventilation and lung ventilation in tadpoles and with fictive lung ventilation in adults. In tadpoles, fictive lung burst frequency was 0.8±0.2 min-1 and did not change significantly with Cl--free aCSF superfusion; however, lung burst amplitude increased by nearly 400 % (P&lt;0.01). Fictive gill ventilation averaged 41.6±3.3 min-1 and was reversibly abolished by Cl--free aCSF. Superfusion with Cl--free aCSF abolished lung bursts in two of seven adult preparations, and overall lung burst frequency decreased from 3.1±0.7 to 0.4±0.03 min-1(P&lt;0.01), but burst amplitude was unchanged. Low concentrations of GABA (0.5 mmol l-1) produced a significant increase in lung burst frequency followed by almost complete inhibition at 5.0 mmol l-1,accompanied by the abolition of gill ventilation at 2.5-5.0 mmol l-1. By contrast, fictive lung ventilation in adults was inhibited in a dose-dependent manner by glycine and GABA, and inhibition occurred at approximately 10-fold lower concentrations compared with tadpoles. The glycine receptor antagonist strychnine (2.5-25.0 μmol l-1) and the GABAA receptor antagonist bicuculline (1-10 μmol l-1)inhibited fictive gill ventilation and increased fictive lung ventilation in tadpoles. However, bicuculline and strychnine inhibited fictive lung ventilation in adults. These results suggest that lung ventilation in the tadpole brainstem may be driven by a pacemaker-like mechanism since Cl--free aCSF failed to abolish lung ventilation. Lung ventilation in adults and gill ventilation in tadpoles, however, appear to be dependent upon conventional Cl--mediated synaptic inhibition. Thus, there may be a developmental change in the fundamental process driving lung ventilation in amphibians. We hypothesize that maturation of the bullfrog respiratory CPG reflects developmental changes in glycinergic and/or GABAergic synaptic inhibitory mechanisms.

Central respiratory activity of the tadpole in vitro brain stem is modulated diversely by nitric oxide

2002 ◽  
Vol 283 (2) ◽  
pp. R417-R428 ◽  
Author(s):  
Michael B. Harris ◽  
Richard J. A. Wilson ◽  
Konstantinon Vasilakos ◽  
Barbara E. Taylor ◽  
John E. Remmers
Keyword(s):  
Nitric Oxide ◽  
Rana Catesbeiana ◽  
Lung Ventilation ◽  
Central Chemosensitivity ◽  
Respiratory Rhythmogenesis ◽  
Specific Frequency ◽  
Central Respiratory Activity ◽  
Ph Conditions ◽  
Respiratory Rhythms

Nitric oxide (NO) is a potent central neuromodulator of respiration, yet its scope and site of action are unclear. We used 7-nitroindazole (7-NI), a selective inhibitor of endogenous neuronal NO synthesis, to investigate the neurogenesis of respiration in larval bullfrog ( Rana catesbeiana) isolated brain stems. 7-NI treatment (0.0625–0.75 mM) increased the specific frequency of buccal ventilation (BV) events, indicating influence on BV central rhythm generators (CRGs). The drug reduced occurrence, altered burst shape, and disrupted clustering of lung ventilation (LV) events, without altering their specific frequency. LV burst occurrence and clustering also differed between pH conditions. We conclude that NO has diverse effects on respiratory rhythmogenesis, being necessary for the expression of respiratory rhythms, inhibiting the frequency of BV CRG, and affecting both shape and clustering of LV bursts through conditional modulation of LV CRG. We confirm central chemosensitivity in these preparations and demonstrate chemomodulation of LV burst clustering and occurrence but not specific frequency. Results support distinct oscillators underlying LV and BV CRGs.

Metabolism and cardiovascular effects of leukotrienes in warm- and cold-acclimated American bullfrogs (Rana catesbeiana)

1991 ◽  
Vol 260 (5) ◽  
pp. R834-R838
Author(s):  
C. A. Herman ◽  
G. A. Charlton ◽  
R. L. Cranfill
Keyword(s):  
Time Course ◽  
Rana Catesbeiana ◽  
Cardiovascular Effects ◽  
Leukotriene C4 ◽  
Gamma Glutamyl Transpeptidase ◽  
Leukotriene D4 ◽  
Inactivation Mechanism ◽  
Glutamyl Transpeptidase

Sulfidopeptide leukotrienes are important mediators in mammals, but much less is known of their metabolism and action in nonmammalian vertebrates. This study examines the cardiovascular effects of leukotrienes on blood pressure and heart rate and compares the metabolism of leukotrienes in vivo and in vitro in warm- and cold-acclimated bullfrogs. Leukotriene C4 (LTC4) is more potent than leukotriene D4 (LTD4) and leukotriene E4 (LTE4) in eliciting hypotension. The leukotrienes are more potent in warm-acclimated animals. Conversion of [3H]LTC4 to [3H]LTD4 occurs rapidly in warm-acclimated bullfrogs, with 15.2 +/- 1.7% of the [3H]LTC4 remaining at 1.5 min. Conversion is slower in vivo in cold-acclimated frogs, with 20.2 +/- 1.7% of the [3H]LTC4 remaining by 6 min. In blood taken from warm-acclimated frogs, conversion of [3H]LTC4 to [3H]LTD4 occurs more rapidly at 22 than at 5 degrees C. This pattern is similar in blood taken from cold-acclimated frogs, suggesting that no modification of gamma-glutamyl transpeptidase occurs at low temperature. [3H]LTE4 production is not observed in vivo or in vitro during the time course of the experiments. The rapid metabolism of LTC4 to LTD4 may represent an inactivation mechanism in amphibians. The cardiovascular effects of LTC4 in vivo may be much greater than current measurements indicate because of rapid conversion of LTC4 to the less potent LTD4.

Sign in / Sign up

Export Citation Format

Share Document