Electrophysiological and neurochemical effects of long-term vagus nerve stimulation on the rat monoaminergic systems
Bibliographic record
Abstract
Vagus nerve stimulation (VNS) is an adjunctive treatment for resistant epilepsy and depression. Electrophysiological recordings in the rat brain have already shown that chronic VNS increases norepinephrine (NE) neuronal firing activity and, subsequently, that of serotonin (5-HT) neurons through an activation of their excitatory α1-adrenoceptors. Long-term VNS was shown to increase the tonic activation of post-synaptic 5-HT1A receptors in the hippocampus. This study was aimed at examining the effect of VNS on extracellular 5-HT, NE and dopamine (DA) levels in different brain areas using in vivo microdialysis, on NE transmission in the hippocampus, and DA neuronal firing activity using electrophysiology. Rats were implanted with a VNS device and stimulated for 14 d with standard parameters used in treatment-resistant depression (0.25 mA, 20 Hz, 500 μs, 30 s on-5 min off). The results of the present study revealed that 2-wk VNS significantly increased extracellular NE levels in the prefrontal cortex and the hippocampus and enhanced the tonic activation of post-synaptic α2-adrenoceptors on pyramidal neurons. The electrophysiological experiments revealed a significant decrease in ventral tegmental area DA neuronal firing rate after long-term VNS; extracellular DA levels were nevertheless increased in the prefrontal cortex and nucleus accumbens. Chronic VNS significantly increased extracellular 5-HT levels in the dorsal raphe but not in the hippocampus and prefrontal cortex. In conclusion, the effect of VNS in increasing the transmission of monoaminergic systems targeted in the treatment of resistant depression should be involved, at least in part, in its antidepressant properties observed in patients not responding to many antidepressant strategies.
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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) | 0.001 | 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".