Opioid peptide-receptor

Pasternak GW (2001) Incomplete cross tolerance and multiple p opioid peptide receptors. Trend Pharmacol Sci 22 67-70... 

Ni Q., Xu H., Partilla J. et al. Opioid peptide receptor studies. Interaction of opioid peptides and other drugs with four subtypes of the K2 receptor in guinea pig brain. Peptides. 16 1083, 1995. 

Opioid Peptide Receptors. The nature and biologic regulation of opioid receptors have received enormous attention since 1973, when their presence in vertebrate brain homogenates was reported independently by three separate laboratories. In recent years it has become clear from phar-... 

A novel endogenous opioid peptide with significant sequence homology to dynorphin A was alternatively termed nociceptin or orphanin FQ (now termed N/OFQ Table 21-1). The substitution of Phe for Tyr in the opioid motif is sufficient to abolish interactions with the three classical opioid peptide receptors. N/OFQ has behavioral and pain modulatory properties distinct from those of the three classical opioid peptides. 

Activation of metabotropic receptors located presynaptically results in the inhibition of calcium influx with a resultant decrease in the relea.se of neurotransmitter from nerve endings. This type of presynaptic inhibition occurs following activation of dopamine D, norepinephrine alpha, glutamate, and mu opioid peptide receptors. The answer is (A). 

The second application of the CFTI protocol is the evaluation of the free energy differences between four states of the linear form of the opioid peptide DPDPE in solution. Our primary result is the determination of the free energy differences between the representative stable structures j3c and Pe and the cyclic-like conformer Cyc of linear DPDPE in aqueous solution. These free energy differences, 4.0 kcal/mol between pc and Cyc, and 6.3 kcal/mol between pE and Cyc, reflect the cost of pre-organizing the linear peptide into a conformation conducive for disulfide bond formation. Such a conformational change is a pre-requisite for the chemical reaction of S-S bond formation to proceed. The predicted low population of the cyclic-like structure, which is presumably the biologically active conformer, agrees qualitatively with observed lower potency and different receptor specificity of the linear form relative to the cyclic peptide. 

The opioid peptides vary in their binding affinities for the multiple opioid receptor types. Leu- and Met-enkephalin have a higher affinity for 5-receptors than for the other opioid receptor types (68), whereas the dynorphin peptides have a higher affinity for K-sites (69). P-Endorphin binds with equal affinity to both p- and 5-receptors, but binds with lower affinity to K-sites (70). The existence of a P-endorphin-selective receptor, the S-receptor, has been postulated whether this site is actually a separate P-endorphin-selective receptor or is a subtype of a classical opioid receptor is a matter of controversy (71,72). The existence of opioid receptor subtypes in general is quite controversial although there is some evidence for subtypes of p- (73), 5-(74), and K-receptors (72,75), confirmation of which may be obtained by future molecular cloning studies. 

Nociceptin and orphanin are synonyms for the peptide that acts at an opioid-like receptor. Nociceptin may act by inhibiting tachykinin release from sensory C-fibres, and a clinical trial has started to test its effects on cough. 

Endogenous opioid peptides are the wide variety of endogenous peptides isolated since 1975 which are the natural ligands for the opioid receptors. The peptides... 

Nociceptin is an opioid peptide, which is the endogenous ligand for the opioid receptor-like protein (ORL). 

Opioid receptors Endogenous opioid peptides Noci-ceptin/orphanin FQ ORL-1... 

A 17 amino acid long peptide sequentially related to opioid peptides in particular dynorphin A. OFQ/N is inactive at the 5, k, and p opioid receptors, but binds to its own NOP receptor (formerly ORL-1, for opioid receptor like-1). In contrast to opioid peptides, OFQ/N has no direct analgesic properties. OFQ/N is the first example for the discovery of a novel neurotransmitter from tissue extracts by using an orphan receptor as bait. Centrally administered in rodents, OFQ/N exerts anxiolytic properties. OFQ/N agonists and antagonists... 

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