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Multiple tachykinin binding sites in peripheral tissues and in brain.
European Journal of Pharmacology
|November 4, 1986
Summary
This study compares tachykinin binding sites in various tissues. Results reveal distinct receptor subtypes in peripheral tissues and the central nervous system, suggesting a new SP-N receptor category.
Area of Science:
- Pharmacology
- Neuroscience
- Biochemistry
Background:
- Tachykinins are peptide neurotransmitters involved in various physiological processes.
- Different tachykinin receptor subtypes exist, exhibiting varied affinities for specific ligands.
- Understanding these receptor subtypes is crucial for developing targeted therapeutics.
Purpose of the Study:
- To characterize and compare tachykinin binding sites in guinea pig urinary bladder (GPUB), rat salivary gland (RSG), hamster urinary bladder (HUB), rat vas deferens (RVD), and rat cerebral cortex (RCC).
- To investigate the relative potencies of substance P (SP), neurokinin A (NKA), and eledoisin (ELE) analogues at these binding sites.
- To identify potential novel tachykinin receptor subtypes.
Main Methods:
- Radioligand binding assays were performed using 125I-Bolton Hunter conjugates of substance P (125I-BHSP), eledoisin (125I-BHE), and neurokinin A (125I-BHNKA).
- Competition binding experiments were conducted using various tachykinin analogues, including SP methyl ester (SPOMe) and modified SP peptides.
- Binding site characteristics were analyzed based on the displacement potency of different ligands.
Main Results:
- Peripheral tissues like GPUB and RSG showed characteristics of SP-P receptors, with SP being the most potent displacer.
- Peripheral tissues like HUB and RVD exhibited SP-E receptor characteristics, with NKA as the most potent displacer.
- Rat cerebral cortex (RCC) displayed a distinct binding profile, with neurokinin B being the most potent displacer of 125I-BHE, suggesting a novel receptor subtype (SP-N).
Conclusions:
- Tachykinin binding sites in peripheral tissues can be classified into SP-P and SP-E types based on ligand displacement patterns.
- The central nervous system (CNS) possesses a distinct tachykinin receptor subtype, potentially designated SP-N, differing from peripheral receptors.
- These findings highlight the heterogeneity of tachykinin receptors and provide a basis for further pharmacological characterization and drug development.