Histamine facilitates <i>in vivo</i> thalamocortical long‐term potentiation in the mature visual cortex of anesthetized rats
Bibliographic record
Abstract
Recent evidence indicates that the mature central visual system retains a higher degree of plasticity than traditionally assumed. However, little is known regarding the neuromodulatory factors that influence plasticity in the adult primary visual cortex (V1). We investigated the role of histamine, one of the neuromodulators that densely innervate all neocortical fields, in modulating plasticity of V1 by examining thalamocortical long-term potentiation (LTP). Theta-burst stimulation of the lateral geniculate nucleus of urethane-anesthetized rats resulted in potentiation of the field postsynaptic potential recorded in the superficial layers of V1. Histamine (0.01-10 mM), applied locally in V1 by reverse microdialysis, produced a clear, dose-dependent enhancement of LTP. In addition, histamine also allowed a weak theta-burst induction protocol, that by itself failed to induce significant synaptic potentiation, to produce stable LTP. The effect of histamine to facilitate LTP was largely resistant to blockade of H(1)[chlorpheniramine, 5 and 10 mg/kg, intraperitoneal (i.p.)] or H(2) receptors (cimetidine, 10 mg/kg, zolantidine, 5 mg/kg, i.p.). However, arcaine sulfate salt (10 mg/kg, i.p.), a blocker of the polyamine binding site of the N-methyl-D-aspartate (NMDA) receptor, completely antagonized the LTP amplification induced by histamine, suggesting that it acts via a direct modulation of NMDA receptors, rather than histaminergic receptor activation. The present experiments provide the first demonstration of a histaminergic influence on neocortical synaptic plasticity in vivo and show that cortical histaminergic activation acts to lower the induction threshold and increase the degree of plasticity in the mature thalamocortical visual system.
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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) | 0.000 | 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) | 0.001 | 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".