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Updated: Aug 11, 2026

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Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
[pGlu6,Pro9]SP6-11, a selective agonist for the substance P P-receptor subtype
Journal of Medicinal Chemistry
|July 1, 1986
Summary
A single amino acid change in substance P analogue [pGlu6]SP6-11 creates [pGlu6,Pro9]SP6-11, a selective SP-P receptor agonist. This peptide distinguishes between muscular and neuronal tachykinin receptors, enabling specific bioassays.
Area of Science:
- Pharmacology
- Neuroscience
- Biochemistry
Background:
- Substance P (SP) is a key neurotransmitter involved in various physiological processes.
- Tachykinin receptors, including SP-P and SP-E subtypes, mediate diverse biological responses.
- Developing selective receptor agonists is crucial for understanding receptor function and for therapeutic applications.
Purpose of the Study:
- To investigate the effect of a single amino acid substitution on the receptor selectivity of a substance P analogue.
- To characterize the activity of the modified peptide, [pGlu6,Pro9]SP6-11, at different tachykinin receptor subtypes.
- To explore the potential of [pGlu6,Pro9]SP6-11 as a tool for selective receptor desensitization and bioassay.
Main Methods:
- Synthesis of a modified hexapeptide analogue of substance P, [pGlu6,Pro9]SP6-11, by substituting proline for glycine-9.
- In vitro assays measuring K+ release from rat parotid slices (SP-P receptor mediated).
- In vitro assays measuring contraction of isolated guinea pig ileum (SP-P and neuronal tachykinin receptors).
- In vitro assays using hamster urinary bladder and rat duodenum preparations (SP-E systems).
Main Results:
- The modified peptide [pGlu6,Pro9]SP6-11 demonstrated selective agonist activity toward the SP-P receptor subtype.
- [pGlu6,Pro9]SP6-11 showed reduced activity on SP-E systems (20-fold less potent than [pGlu6]SP6-11).
- In guinea pig ileum, [pGlu6,Pro9]SP6-11 exhibited significantly lower potency at the neuronal tachykinin receptor compared to the muscular receptor (600-fold difference).
Conclusions:
- Substitution of glycine-9 with proline in [pGlu6]SP6-11 yields a peptide with selective SP-P receptor agonist activity.
- [pGlu6,Pro9]SP6-11 effectively discriminates between muscular and neuronal tachykinin receptors in the guinea pig ileum.
- This selectivity allows for the specific desensitization of the muscular receptor, facilitating a sensitive bioassay for the neuronal receptor.
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