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Opioid receptor distribution in the claustrum-dorsal endopiriform complex
Matthew Bolger1, Jesse Jackson2,3, Anna M W Taylor1,2,4,5
1Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada.
Iscience
|June 15, 2026
Summary
The study maps opioid receptor distribution in the mouse claustrum-dorsal endopiriform. Kappa opioid receptors (Oprk) are mainly in specific excitatory neurons, unlike other opioid receptors.
Area of Science:
- Neuroscience
- Molecular Biology
- Receptor Pharmacology
Background:
- The claustrum and dorsal endopiriform are subcortical regions connected to the neocortex.
- These regions are known to be rich in opioid receptors, but their specific cellular localization is not well understood.
- Opioid receptors play crucial roles in modulating neuronal activity and circuit function.
Purpose of the Study:
- To precisely map the cellular distribution of four opioid receptors (mu, delta, kappa, and ORL1) within the mouse claustrum and dorsal endopiriform.
- To identify specific neuronal populations expressing these receptors.
- To investigate the evolutionary conservation of opioid receptor organization in the claustrum.
Main Methods:
- Multiplexed fluorescent in situ hybridization was used to visualize and quantify opioid receptor gene expression (Oprm, Oprd, Oprk, Oprl) in mouse brain tissue.
- Analysis of single-nucleus RNA sequencing (snRNA-seq) data from macaque claustrum was performed.
- Spatial mapping techniques were employed to determine receptor localization within specific cell types and anatomical subregions.
Main Results:
- Kappa opioid receptor (Oprk) expression was found to be restricted to excitatory neurons, specifically enriched in a subset of Synpr+ claustrum core projection cells.
- Mu (Oprm), delta (Oprd), and ORL1 (Oprl) opioid receptors showed broader expression patterns, found in both excitatory and inhibitory neuronal populations.
- Spatial analysis confirmed the restricted expression of Oprk within the claustrum core.
- Similar opioid receptor distribution patterns were observed in the macaque claustrum, suggesting evolutionary conservation.
Conclusions:
- The study reveals a cell-type-specific and evolutionarily conserved organization of opioid receptor expression in the claustrum-dorsal endopiriform.
- Kappa opioid receptors have a distinct localization pattern compared to other opioid receptors in this region.
- The findings suggest specialized roles for different opioid receptors in modulating claustrocortical circuits.
Keywords:
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