Postsynaptic µ‐opioid receptor response in the median preoptic nucleus is altered by a systemic sodium challenge in rats
Bibliographic record
Abstract
The median preoptic nucleus (MnPO) is an integrator site for the chemosensory and neural signals induced by a perturbation in the hydromineral balance, and it is highly involved in controlling fluid and electrolyte ingestion. Here, we hypothesize that opioid peptides, previously recognized to control ingestive behaviors, may regulate the excitability of MnPO neurons and that this regulatory action may depend on the natriuric (Na(+)) status of body fluid compartments. Our results show that activation of mu-, but not delta-, opioid receptors (OR) triggered a membrane hyperpolarization by recruiting a G-protein-regulated inward-rectifier K(+) (GIRK) conductance in 41% of the neurons tested. Interestingly, 24 h Na(+) depletion strengthened this opioid-mediated control of neuronal excitability. In Na(+)-depleted animals, the neuronal population displaying the mu-OR-induced hyperpolarization expanded to 60% (Z-test, P = 0.012), whereas Na(+) repletion restored this population to the control level (39%; Z-test, P = 0.037). Among the neurons displaying mu-OR-induced hyperpolarization, Na(+) depletion specifically increased the neuronal population responsive to variation in ambient Na(+) (from 27% to 43%; Z-test, P = 0.029). In contrast, Na(+) repletion dramatically reduced the population that was unresponsive to Na(+) (from 17% to 3%; Z-test, P = 0.031). Neither the basic properties of the neurons nor the characteristics of the mu-OR-induced response were altered by the body Na(+) challenge. Our results indicate that an episode of Na(+) depletion/Na(+) repletion modifies the organization of the opioid-sensitive network of the MnPO. Such network plasticity might be related to the avid salt ingestion triggered by repeated Na(+) depletion.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| 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".