Regulation of Opioid Receptors by Their Endogenous Opioid Peptides

2021 ◽  
Author(s):  
Achla Gupta ◽  
Srinivas Gullapalli ◽  
Hui Pan ◽  
Dinah L. Ramos-Ortolaza ◽  
Michael D. Hayward ◽  
...  
Keyword(s):  
Opioid Receptors ◽  
Opioid Peptides ◽  
Endogenous Opioid Peptides ◽  
Endogenous Opioid

Met5-enkephalin protects isolated adult rabbit cardiomyocytes via δ-opioid receptors

1999 ◽  
Vol 277 (6) ◽  
pp. H2442-H2450 ◽  
Author(s):  
Yasushi Takasaki ◽  
Roger A. Wolff ◽  
Grace L. Chien ◽  
Donna M. van Winkle
Keyword(s):  
Cell Death ◽  
Opioid Receptors ◽  
Ischemic Preconditioning ◽  
Opioid Peptides ◽  
Trypan Blue ◽  
Adult Rabbit ◽  
Endogenous Opioid Peptides ◽  
Endogenous Opioid ◽  
Simulated Ischemia ◽  
Hypoxic Incubation

In rats and rabbits, endogenous opioid peptides participate in ischemic preconditioning. However, it is not known which endogenous opioid(s) can trigger cardioprotection. We examined preconditioning-induced and opioid-induced limitation of cell death in isolated, calcium-tolerant, adult rabbit cardiomyocytes. Cells were subjected to simulated ischemia by pelleting and normothermic hypoxic incubation. Preconditioning was elicited with 15 min of simulated ischemia followed by 15 min of resuspension and reoxygenation. All cells underwent 180 min of simulated ischemia. Cell death was assessed by trypan blue permeability. Morphine protected cells, as did preconditioning; naloxone blocked the preconditioning-induced protection. Exogenous Met5-enkephalin (ME) induced protection, but exogenous β-endorphin did not. ME-induced protection was blocked by the δ-selective antagonist naltrindole. Additionally, two other proenkephalin products, Leu5-enkephalin and Met5-enkephalin-Arg-Phe, provided protection equipotent to ME. These data suggest that one or more proenkephalin products interact with δ-opioid receptors to endogenously trigger opioid-mediated protection.

Types of opioid receptors: relation to antinociception

1985 ◽  
Vol 308 (1136) ◽  
pp. 291-297 ◽  
Keyword(s):  
Nervous System ◽  
Opioid Receptors ◽  
Opioid Peptides ◽  
Binding Sites ◽  
Endogenous Opioid Peptides ◽  
Endogenous Opioid ◽  
Narcotic Analgesics ◽  
High Concentrations ◽  
P Type ◽  
Μ Receptor

The endogenous opioid peptides are derived from three large precursors. Pro-opiocortin and proenkephalin yield [Met]enkephalin, carboxy-extended [Met]enkephalins and [Leu]enkephalin. The fragments of prodynorphin are all carboxy-extended [Leu]- enkephalins. Three approaches are of importance for an analysis of the physiological functions of the different endogenous opioid peptides. First, since these peptides interact with more than one of the μ-, δ- and K-binding sites and thus with their receptors, it is necessary to synthesize peptides or non-peptides, which bind to only one of the sites. As far as narcotic analgesics are concerned, morphine fulfils these conditions since it interacts almost exclusively with the μ-receptor. Secondly, antagonists are required that are selective for only one of the opioid receptors, even when used in high concentrations. Finally, it is important to find circumscribed areas in the nervous system that possess only one type of opioid receptor. It is now known that in the rabbit cerebellum the opioid receptors are almost exclusively of the p-type whereas in the guinea-pig cerebellum they are almost exclusively of the K-type.

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