In vitro and in vivo comparison of [<sup>3</sup>H](+)‐PHNO and [<sup>3</sup>H]raclopride binding to rat striatum and lobes 9 and 10 of the cerebellum: A method to distinguish dopamine D<sub>3</sub>from D<sub>2</sub>receptor sites: A method to distinguish dopamine D<sub>3</sub>from D<sub>2</sub>receptor sites
Bibliographic record
Abstract
In vitro binding characteristics of the dopamine D₃/D₂ antagonist [³H]raclopride were compared to the D₃/D₂ agonist [³H](+)-PHNO in membrane preparations from rat striatum, cerebellum Lobules 9 and 10 (CB L9,10), and other cerebellar regions. In striatum, both radioligands labeled a single binding site. [³H](+)-PHNO showed higher affinity, though lower B(max) , compared with [³H]raclopride and was sensitive to inhibition by Gpp(NH)p. [³H](+)-PHNO showed significant specific binding to CB L9,10 membranes with higher affinity compared to striatal membranes. [³H](+)-PHNO binds to a high- and a low-affinity binding site in CB L9,10 membranes; the high-affinity site was not Gpp(NH)p-sensitive. [³H](+)-PHNO did not significantly bind cerebellum left hemisphere membranes. Very low specific binding of [³H]raclopride was found in CB L9,10. The selective dopamine D₃ antagonist SB-277011 did not displace the binding of either ligand to striatal membranes but potently inhibited the binding of [³H](+)-PHNO in CB L9,10 membranes. The highly selective D₂ antagonist SV-156 showed the opposite profile. In vivo experiments were consistent with and supported by in vitro results. In summary, [³H](+)-PHNO and [³H]raclopride mainly label dopamine D₂ receptors in rat striatum, with [³H](+)-PHNO labeling a D₂(High) population. In vitro and in vivo, [³H](+)-PHNO labels CB L9,10 dopamine D₃ receptors that are apparently in a high affinity state whereas [³H]raclopride gave only very low signal in this region. The present approaches appear useful for selectively labeling dopamine D₃ and D₂ receptors in different rat brain regions and offer the possibility to demonstrate D₃ versus D₂ receptor selectivity of compounds using native rat brain tissue.
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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 | 0.001 |
| 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 | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".