Cellular and ionic mechanisms underlying the P2Y <sub>1</sub> receptor‐mediated excitation of thepreBötzinger Complex inspiratory network in vitro
Bibliographic record
Abstract
A host of adaptive responses have evolved to protect brain oxygen levels. Prominent among these is the biphasic hypoxic ventilatory response (HVR), in which a fall in arterial oxygen, detected at the peripheral chemoreceptors triggers a rapid increase in breathing that is followed by a centrally‐mediated secondary hypoxic respiratory depression (HRD). The HRD is most pronounced in premature infants and can be life‐threatening. Our recent data challenge dogma that the only contribution of the CNS to the HVR is this secondary depression. Specifically, in vitro and in vivo data from rat suggest that astrocytes in the pre‐Bötzinger complex (pre‐BötC, critical site for inspiratory rhythm generation) release ATP in response to hypoxia, which acts via P2Y 1 receptors (P2Y 1 Rs) on inspiratory neurons to increase ventilation and attenuate the HRD. In other parts of the brains, P2Y 1 Rs signal via the Gq second messenger pathway, but the signalling cascade(s) and ion channel(s) via which P2Y 1 Rs excite inspiratory neurons to increase inspiratory frequency remain unknown. Previous efforts from our lab to address these questions tested the effects of second messenger and ion channel blockers on ATP currents, but data were confounded by the finding that while P2Y 1 Rs account for the entire network frequency effect, they account for only a fraction (~30%) of the total ATP current. Thus, the first objective of this study was to revisit this question by examining the effects of Gq and ion channel blockers on currents evoked in inspiratory preBötC neurons by the P2Y 1 R agonist, MRS 2365. Our second goal was to determine whether the excitatory effect of P2Y 1 Rs on the preBötC network is mediated through activation of excitatory (glutamatergic) or inhibitory GABA/glycinergic) preBötC neurons. Analysis of whole‐cell recordings from inspiratory preBötC neurons in rhythmic medullary slices from neonatal (P0‐4) SD rats revealed that inward currents evoked by MRS 2365 (30 sec, 100 mM)immediately after obtaining whole‐cell configuration and again after 15 min of dialysis (via the pipette solution) with the protein kinase C (PKC) inhibitor (Chelerethryne, 10 mM, n = 5), the phospholipase C (PLC) inhibitor (U73122 4 mM, n = 6) or the BK Ca channel blocker (paxilline 1 or 4 mM, n = 7), were reduced between 30–40%. To test whether P2Y 1 R‐sensitive, inspiratory neurons are excitatory or inhibitory, we prepared rhythmic slices from transgenic mice (P0‐4) in which glutamatergic (VGLUT2‐TdTomato) or GABAergic (GAD67‐YFP) neurons are fluorescently labeled. Local application of MRS 2365 evoked inward currents in zero of seven VGLUT2‐TdTomato inspiratory neurons. Analysis of GAD67‐YFP inspiratory neurons is ongoing. We are also applying RNAScope analysis to determine the transmitter phenotype of P2Y 1 R‐sensitive inspiratory neurons. These data suggest that P2Y 1 Rs acton non‐glutamatergic, inspiratory neurons, in part via the Gq signalling pathway and BK Ca channels, to excite the preBötC inspiratory rhythm generating network. Support or Funding Information Supported by CIHR, NSERC, CFI, WCHRI and NMHI. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".