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The vanilloid (capsaicin) receptor: receptor types and species differences
1Department of Pharmacology, Menarini Richerche Sud, Pomezia (Roma), Italy.
General Pharmacology
|March 1, 1994
Summary
Researchers identified the vanilloid receptor, a capsaicin receptor, using [3H]resiniferatoxin (RTX) binding. This receptor exhibits heterogeneity in binding affinity and function across different tissues and species, impacting vanilloid actions.
Area of Science:
- Pharmacology
- Neuroscience
- Molecular Biology
Background:
- The existence of a specific capsaicin receptor on primary afferent neurons was long postulated.
- Capsaicin analogs, like resiniferatoxin (RTX), exhibit unique pharmacological actions.
Purpose of the Study:
- To demonstrate the existence of the capsaicin receptor.
- To characterize the binding properties and heterogeneity of the vanilloid receptor.
Main Methods:
- Utilized [3H]resiniferatoxin ([3H]RTX) binding assays.
- Investigated binding affinity, cooperativity, and antagonist interactions (capsazepine).
- Assessed receptor characteristics across various tissues and species, including rat, guinea pig, hamster, rabbit, and human post-mortem spinal cord.
Main Results:
- Demonstrated specific [3H]RTX binding, confirming the vanilloid receptor.
- Observed significant heterogeneity in RTX binding affinity and cooperativity between central and peripheral vanilloid receptors.
- Identified interspecies differences in vanilloid receptor characteristics, correlating with species sensitivity to vanilloid compounds.
- Found that reducing agents influence [3H]RTX binding affinity, suggesting a role for endogenous reducing agents.
Conclusions:
- The vanilloid receptor exists and displays significant intraspecies heterogeneity and interspecies differences.
- RTX binding assays provide a tool to study vanilloid receptor function and identify potential endogenous ligands and receptor superfamily affiliations.