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Biochemical Evidence of Functional Interaction Between μ‐ and δ‐Opioid Receptors in SK‐N‐BE Neuroblastoma Cell Line
Author(s) -
Palazzi Elisabetta,
Ceppi Elena,
Guglielmetti Filippo,
Catozzi Lidia,
Amoroso Daniela,
Groppetti Antonio
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67010138.x
Subject(s) - damgo , adenylyl cyclase , agonist , chemistry , receptor , enkephalin , medicine , pertussis toxin , endocrinology , (+) naloxone , μ opioid receptor , opioid , partial agonist , g protein , opioid receptor , pharmacology , biology , biochemistry
Radioligand binding assays and functional experiments revealed that the SK‐N‐BE neuroblastoma cell line expresses a similar ratio of μ‐ and δ‐opioid receptors, both negatively coupled to adenylyl cyclase through pertussis toxin‐sensitive G proteins. Our findings also indicate that some functional interaction occurred between the two opioid subtypes; in fact, long‐term exposure to [ d ‐Ala 2 ‐ N ‐methyl‐Phe 4 ‐Gly‐ol 5 ]enkephalin (DAMGO), a μ‐selective agonist, sensitized the functional response of the δ‐selective agonist but not vice versa. It is interesting that in acute interaction experiments, we observed a shift to the right of the concentration‐effect curve of either DAMGO or [ d ‐Pen 2,5 ]enkephalin (DPDPE), a δ‐selective agonist, as a result of DPDPE or DAMGO administration, respectively. In addition, low doses of naloxone, an antagonist selective for μ receptors, increased the inhibitory effect of [ d ‐Ala 2 , d ‐Met 5 ]enkephalinamide (DAME), a mixed μ/δ agonist, on adenylyl cyclase activity. Taken overall, these data support the hypothesis of the existence of a cross talk between μ and δ receptors in the SK‐N‐BE cell line.