Premium
Acute and Chronic Effects of Opioids on δ and μ Receptor Activation of G Proteins in NG108‐15 and SK‐N‐SH Cell Membranes
Author(s) -
Breivogel Christopher S.,
Selley Dana E.,
Childers Steven R.
Publication year - 1997
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.1471-4159.1997.68041462.x
Subject(s) - membrane , receptor , chemistry , pharmacology , cell , neuroscience , microbiology and biotechnology , medicine , biophysics , biochemistry , biology
To compare activation of G proteins by opioid receptors, opioid agonist‐stimulated guanosine 5′‐ O ‐(3‐[ 35 S]thiotriphosphate) ([ 35 S]GTPγS) binding in the presence of excess GDP was assayed in membranes from NG108‐15 (δ) and SK‐N‐SH (primarily μ) cells. Basal [ 35 S]GTPγS binding consisted of a single class of low‐affinity sites ( K D 400–500 n M ). Addition of agonists produced a high‐affinity site 100–300‐fold higher in affinity than the basal site. The receptor/transducer amplification factor (ratio of activated G protein B max to opioid receptor B max ) was 10‐fold higher for SK‐N‐SH μ receptors than for NG108‐15 δ receptors. Chronic δ agonist ([ d ‐Ser 2 ]‐Leu‐enkephalin‐Thr; DSLET) treatment of NG108‐15 cells resulted in an 80% loss of DSLET‐stimulated [ 35 S]GTPγS binding within 1 h. Morphine treatment of SK‐N‐SH cells decreased μ agonist ([ d ‐Ala 2 , N ‐Me‐Phe 4 ,Gly 5 ‐ol]‐enkephalin; DAMGO)‐stimulated [ 35 S]GTPγS binding by 45% after 16 h, with no effect after 1 h. Loss of agonist response was due to a decrease in the B max of activated G proteins with no change in the K D . These results provide a quantitative description of G protein activation occurring on acute and chronic exposure to opioid agonists.