The Regulatory Properties of α5 Subunit-Containing γ-Aminobutyric Acid Subtype A Receptors in Learning and Synaptic Plasticity
Bibliographic record
Abstract
Synaptic plasticity, which is thought to represent the neuronal substrate for learning and memory is influenced by the degree of GABAergic inhibitory tone. In particular, γ-aminobutyric acid subtype A receptors (GABAARs), which mediate the majority of inhibitory neurotransmission in the mammalian brain regulate learning and plasticity. In these studies I examined a subpopulation of α5 subunit-containing GABAA receptors (α5GABAARs), which are preferentially expressed in the hippocampus, to determine whether they have a specific role in memory processes. I hypothesized that α5GABAAR-activity constrains hippocampus-dependent learning and CA1 synaptic plasticity. The main research objective of this thesis was to investigate the electrophysiological changes within the hippocampus that accompany genetic and pharmacological targeting of α5GABAARs and how these changes impact behaviour. \n\nI found that the general anesthetic etomidate enhanced a tonic inhibitory conductance generated by α5GABAARs, and this action correlated with an impairment of long-term potentiation (LTP) and hippocampus-dependent memory performance for fear-associated memory and spatial navigation. Mice with a genetic deletion of the α5 subunit gene (Gabra5–/–) were resistant to the LTP- and memory-impairing effects of etomidate. Additionally, the LTP- and memory-impairing effects of etomidate were rescued by pharmacologically inhibiting α5GABAARs. Genetic and pharmacological inhibition of α5GABAARs enhanced associative learning in trace fear but not contextual fear conditioning tasks. Interestingly, genetic deletion and pharmacological inhibition of α5GABAARs did not result in the common adverse side-effects associated with non-selective inhibition of GABAARs such as anxiogenesis or seizures. Further, I found that blocking the tonic inhibition generated by α5GABAARs lowered the threshold for LTP, such that lower stimulation frequencies enhanced LTP. Synaptic changes within this frequency band were modified independently of phasic GABAAR inhibition. Inhibiting the α5GABAAR-dependent membrane conductance was associated with an increase in the depolarizing envelope during 10 Hz stimulation. These experiments provide new insights into the in vitro and in vivo physiology of α5GABAARs and suggest that a tonic inhibition generated by α5GABAARs constrains learning and glutamate plasticity through regulation of the membrane’s electrical properties.
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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) | 0.000 | 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 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".