Intravenous Anesthetics Are More Effective than Volatile Anesthetics on Inhibitory Pathways in Rat Hippocampal CA1
Bibliographic record
Abstract
In this study, we have examined the effects of both volatile and IV general anesthetics on excitatory synaptic transmission, with and without recurrent inhibition, to clarify whether excitatory or inhibitory synapses are the major targets of action. Field population spike amplitudes (fPSs) of CA1 pyramidal neurons were recorded in rat hippocampal slices. Schaffer-collateral-commissural fibers (Sch) were stimulated orthodromically, and the evoked fPSs (PS[Sch]) in CA1 area were measured. In addition, the fPSs (PS[Alv+Sch]) elicited by stimulation of the Sch after antidromic stimulation of the alveus hippocampi (Alv) to produce recurrent inhibition were determined. It was observed that sevoflurane (0.5%-5%) and isoflurane (0.5%-5%) primarily inhibited PS[Sch] and also produced additive inhibition on the PS[Alv+Sch] in a concentration-dependent manner. The calculated 50% effective concentration (EC50) values for PS[Sch] and PS[Alv+Sch] were 5.3 vol% and 3.9 vol% (sevoflurane) and 1.7 vol% and 1.1 vol% (isoflurane), respectively. In comparison, thiopental (2.0 x 10(-5)-5.0 x 10(-4) mol/L) reduced both the PS[Sch] and PS[Alv+Sch] in a concentration-dependent manner. The calculated EC50 values for thiopental on PS[Sch] and PS[Alv+Sch] were 3.4 x 10(-4) and 5.7 x 10(-5) mol/L, respectively. Propofol (2.0 x 10(-5)-3.5 x 10(-4) mol/L) had little effect on the PS[Sch] but reduced PS[Alv+Sch] with a calculated EC(50) value of 5.1 x 10(-4) mol/L. The effects of the IV anesthetics with recurrent inhibition were antagonized in the presence of the gamma-aminobutyric acid-A-receptor antagonist bicuculline methiodide. In addition, all anesthetics prolonged recurrent inhibition from 100 ms (sevoflurane and isoflurane) to 400 ms (propofol). The results suggest that sevoflurane and isoflurane inhibit mainly on glutamate-mediated orthodromic pathways, whereas thiopental and propofol enhance gamma-aminobutyric acid-A-mediated recurrent inhibitory pathways in CA1 neurons, thus providing further evidence that the mechanisms of general anesthetics are drug- and pathway-specific.
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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) | 0.001 | 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".