ATP Excitation of the PreBötzinger Complex and Inspiratory Neurons <i>in vitro</i> is Mediated in Part via a PLC/IP <sub>3</sub> ‐mediated increase In [Ca <sup>2+</sup> ] <sub>i</sub>
Bibliographic record
Abstract
The ventilatory response to hypoxia comprises an initial increase in ventilation followed by a secondary depression that can be life‐threatening in premature infants. ATP released within the ventral respiratory column, including the preBötzinger Complex (preBötC, critical site for inspiratory rhythm generation), during hypoxia attenuates this depression. Astrocytes sense hypoxia via a mitochondrial mechanism that involves mitochondrial depolarization, free radical production, lipid peroxidation, phospholipase C (PLC) and inositol trisphosphate (IP 3 ) activation followed by an increase in intracellular Ca 2+ and vesicular ATP release. Our working hypothesis is that ATP released from preBötC astrocytes during hypoxia acts in an autocrine/paracrine manner to enhance gliotransmission and also excites local inspiratory neurons directly via a P2Y 1 receptor (R)‐dependent mechanism to increase inspiratory frequency (freq). Our first objective was to determine if the ATP excitation of inspiratory neurons includes an astrocytic glutamate component (i.e., do astrocytes release glutamate in response to P2Y 1 receptor activation?). Using 700 μm rhythmically‐active medullary slices, we obtained whole‐cell recordings from preBötC inspiratory neurons and compared neuronal ATP (5 mM) currents evoked before and after bath application of glutamate R antagonists AP5 (100 μM) and CNQX (10 μM) (in 0.5 μM TTX). AP5 and CNQX had no effect on ATP currents (n=8). Our second objective was to identify the signaling pathways through which ATP excites the preBötC network and neurons. Simultaneous application of the PLC blocker U73122 (20 μM) to the bath (20 μM) and into the preBötC (10 μM) via pressure injection shortened the duration of MRS2365 (100 μM)‐evoked frequency increase but had no effect on the peak frequency (n=9). 2‐APB (100 μM), an IP 3 R inhibitor, reduced the ATP‐evoked freq increase from 232.14 ± 39% to 147 ± 12% (n=5). In contrast, intracellular dialysis of U73122 (2 μM, n=6) and 2‐APB (50 μM, n=4) attenuated ATP‐evoked inward currents in inspiratory neurons by 50 ± 7% and 42 ± 17%, respectively. Bath application of U73122 had no effect on the ATP‐induced inward current (n=4), suggesting that bath‐applied U73122 does not access the neurons. Intracellular dialysis of sarco/endoplasmic reticulum Ca 2+ ‐ATPase (SERCA) blocker thapsigargin (4 μM, n=3) also attenuated the ATP‐induced inward currents in inspiratory neurons by 29.3 ± 1.03%. These data suggest that although the excitation of preBötC inspiratory neurons by ATP does not include a glial‐derived glutamatergic component, network excitation is brought about, at least in part, via activation in inspiratory neurons of a PLC, IP 3 receptor‐mediated release of Ca 2+ from intracellular stores. Support or Funding Information Supported by CIHR, AIHS, CFI, WCHRI and ALA.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".