Function of NMDA Receptors and Persistent Sodium Channels in a Feedback Pathway of the Electrosensory System
Bibliographic record
Abstract
Voltage-dependent amplification of ionotropic glutamatergic excitatory postsynaptic potentials (EPSPs) can, in many vertebrate neurons, be due either to the intrinsic voltage dependence of N-methyl-D-aspartate (NMDA) receptors, or voltage-dependent persistent sodium channels expressed on postsynaptic dendrites or somata. In the electrosensory lateral line lobe (ELL) of the gymnotiform fish Apteronotus leptorhynchus, glutamatergic inputs onto pyramidal cell apical dendrites provide a system where both amplification mechanisms are possible. We have now examined the roles for both NMDA receptors and sodium channels in the control of EPSP amplitude at these synapses. An antibody specific for the A. leptorhynchus NR1 subunit reacted strongly with ELL pyramidal cells and were particularly abundant in the spines of pyramidal cell apical dendrites. We have also shown that NMDA receptors contributed strongly to the late phase of EPSPs evoked by stimulation of the feedback fibers terminating on the apical dendritic spines; further, these EPSPs were voltage dependent. Blockade of NMDA receptors did not, however, eliminate the voltage dependence of these EPSPs. Blockade of somatic sodium channels by local somatic ejection of tetrodotoxin (TTX), or inclusion of QX314 (an intracellular sodium channel blocker) in the recording pipette, reduced the evoked EPSPs and completely eliminated their voltage dependence. We therefore conclude that, in the subthreshold range, persistent sodium currents are the main contributor to voltage-dependent boosting of EPSPs, even when they have a large NMDA receptor component.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".