Hypothalamus mediates cardioinhibitory pathway from the paraventricular nucleus of the thalamus
Bibliographic record
Abstract
The paraventricular nucleus of the thalamus (PVT) is known to function as a site of integration of brainstem, limbic and cortical afferent information involved in affective behaviors, and visceral and homeostatic regulation. This study investigated the role of the hypothalamus in mediating the arterial pressure (AP) and heart rate (HR) changes elicited by activation of PVT neurons. In the first series of experiments, cardiovascular responsive sites were identified in PVT using L‐glutamate (Glu; 10 nl, 0.25 M) microinjections in chloralose‐anesthetized Wistar rats. Glu injections in the anterior PVT elicited decreases in mean AP (MAP, −20 ± 3 mmHg) and HR (−15 ± 5 bpm). In the second series, iontophoretic injections of the anterograde tract tracer PHA‐L (2.5%) were made at these depressor sites in the anterior PVT in Wistar rats. Within the hypothalamus, PHA‐L labelled fibers and presumptive terminals were predominantly found bilaterally in and around the anterior, dorsolateral and the ventromedial parvocellular components of the paraventricular nucleus of the hypothalamus (PVH). A few scattered PHA‐L labelled fibers were also observed within the posterior magnocellular component of PVH, the supraoptic nucleus, the lateral and dorsomedial hypothalamic areas, and the area of the tuber cinereum. In the final series, bilateral microinjection (100 nl) of either the synaptic blocker CoCl 2 , the non‐specific Glu antagonist kynurenic acid or the selective NMDA receptor antagonists 2‐amino‐5‐phosphonovalerate were made into the PVH in chloralose‐anesthetized Wistar rats. Injections of these compounds did not significantly alter the resting level of AP or HR. However, all injected compounds attenuated the MAP responses (grouped data; −15 ± 5 mmHg; p<0.01), and completely blocked the HR responses (grouped data, −3 ± 5 bpm; p<0.01) to PVT neuronal activation (control responses; MAP, −25 ± 3 mmHg; HR, −19 ± 7). These data suggest that PVT functions to alter cardiac sympathoinhibitory responses associated with arousal, stress, and affective behaviors through a glutamatergic pathway relaying in PVH. Support or Funding Information Supported in part by the Heart and Stroke Foundation of Ontario
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".