Mu and Delta Opioid Receptors Are Coexpressed and Functionally Interact in the Enteric Nervous System of the Mouse Colon

• Published in: Cellular and molecular gastroenterology and hepatology Vol. 9; no. 3; pp. 465 - 483
• Main Authors: DiCello, Jesse J., Carbone, Simona E., Saito, Ayame, Rajasekhar, Pradeep, Ceredig, Rhian A., Pham, Vi, Valant, Celine, Christopoulos, Arthur, Veldhuis, Nicholas A., Canals, Meritxell, Massotte, Dominique, Poole, Daniel P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2020; Philadelphia, PA : American Gastroenterological Association; Elsevier
• Subjects: Analgesics, Opioid - pharmacology; Animals; Benzamides - pharmacology; CHO Cells; Colon - metabolism; Cricetulus; Enteric Nervous System - drug effects; Enteric Nervous System - metabolism; G Protein-Coupled Receptor; Gastrointestinal Motility - drug effects; Gastrointestinal Motility - physiology; Gene Knock-In Techniques; Genes, Reporter - genetics; Green Fluorescent Proteins - genetics; Heterologous Desensitization; Heteromer; Human health and pathology; Humans; Hépatology and Gastroenterology; Life Sciences; Luminescent Proteins - genetics; Mice; Morphine - pharmacology; Neurobiology; Neurons and Cognition; Opioid Receptor; Original Research; Piperazines - pharmacology; Piperidines - pharmacology; Protein Multimerization - physiology; Receptors, Opioid, delta - agonists; Receptors, Opioid, delta - genetics; Receptors, Opioid, delta - metabolism; Receptors, Opioid, mu - agonists; Receptors, Opioid, mu - genetics; Receptors, Opioid, mu - metabolism; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Red Fluorescent Protein; Heterologous Desensitization; GI; RT; DAMGO; DMSO; DOR; IR; ENS; Opioid Receptor; GFP; OBD; MOR; G Protein-Coupled Receptor; Heteromer; EFS; NFM; IPAN; NLT; nNOS; ChAT; NK3R; GPCR; NK1R; CalR
• ISSN: 2352-345X; 2352-345X
• DOI: 10.1016/j.jcmgh.2019.11.006

Functional interactions between the mu opioid receptor (MOR) and delta opioid receptor (DOR) represent a potential target for novel analgesics and may drive the effects of the clinically approved drug eluxadoline for the treatment of diarrhea-predominant irritable bowel syndrome. Although the enteric nervous system (ENS) is a likely site of action, the coexpression and potential interaction between MOR and DOR in the ENS are largely undefined. In the present study, we have characterized the distribution of MOR in the mouse ENS and examined MOR-DOR interactions by using pharmacologic and cell biology techniques.
MOR and DOR expression was defined by using MORmCherry and MORmCherry–DOR-eGFP knockin mice. MOR-DOR interactions were assessed by using DOR-eGFP internalization assays and by pharmacologic analysis of neurogenic contractions of the colon.
Although MOR was expressed by approximately half of all myenteric neurons, MOR-positive submucosal neurons were rarely observed. There was extensive overlap between MOR and DOR in both excitatory and inhibitory pathways involved in the coordination of intestinal motility. MOR and DOR can functionally interact, as shown through heterologous desensitization of MOR-dependent responses by DOR agonists. Functional evidence suggests that MOR and DOR may not exist as heteromers in the ENS. Pharmacologic studies show no evidence of cooperativity between MOR and DOR. DOR internalizes independently of MOR in myenteric neurons, and MOR-evoked contractions are unaffected by the sequestration of DOR.
Collectively, these findings demonstrate that although MOR and DOR are coexpressed in the ENS and functionally interact, they are unlikely to exist as heteromers under physiological conditions.
[Display omitted]