Modulation of spike clustering by NMDA receptors and neurotensin in rat supraoptic nucleus neurons
Bibliographic record
Abstract
Key points Magnocellular neurosecretory cells (MNCs) of the rat supraoptic nucleus adopt bursting activity patterns under conditions demanding maximum peptide release from their nerve endings in the neurohypophysis. Exogenous activation of NMDA receptors (NMDARs) induces spike clustering in MNCs through a mechanism that requires apamin‐sensitive small conductance calcium‐activated K+ (SK) channels). Here we show that NMDAR‐ and SK channel‐dependent spike clustering can be induced in MNCs by release of endogenous glutamate from afferent axon terminals. This form of bursting activity can be modulated by subtle changes in membrane voltage, or by partial inhibition of SK channels. Abstract Magnocellular neurosecretory cells (MNCs) in the rat supraoptic nucleus display clustered firing during hyperosmolality or dehydration. This response is beneficial because this type of activity potentiates vasopressin secretion from axon terminals in the neurohypophysis and thus promotes homoeostatic water reabsorption from the kidney. However, the mechanisms which lead to the generation of clustering activity in MNCs remain unknown. Previous work has shown that clustered firing can be induced in these neurons through the pharmacological activation of NMDA receptors (NMDARs) and that silent pauses observed during this activity are mediated by apamin‐sensitive calcium activated potassium (SK) channels. However, it remains unknown if clustered firing can be induced in situ by endogenous glutamate release from axon terminals. Here we show that electrical stimulation of glutamatergic osmosensory afferents in the organum vasculosum lamina terminalis (OVLT) can promote clustering in MNCs via NMDARs and apamin‐sensitive channels. We also show that the rate of spike clustering induced by NMDA varies as a bell‐shaped function of voltage, and that partial inhibition of SK channels can increase cluster duration and reduce the rate of clustering. Finally, we show that MNCs express neurotensin type 2 receptors, and that activation of these receptors can simultaneously depolarize MNCs and suppress clustered firing induced by bath application of NMDA or by repetitive stimulation of glutamate afferents. These studies reveal that spike clustering can be induced in MNCs by glutamate release from afferent nerve terminals and that that this type of activity can be fine‐tuned by neuromodulators such as neurotensin.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".