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Effect of Ethanol Self‐Administration on μ‐ and δ‐Opioid Receptor‐Mediated G‐Protein Activity
Author(s) -
SimSelley Laura J.,
Sharpe Amanda L.,
Vogt Leslie J.,
Brunk Leah K.,
Selley Dana E.,
Samson Herman H.
Publication year - 2002
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/j.1530-0277.2002.tb02592.x
Subject(s) - gtpgammas , chemistry , medicine , endocrinology , nucleus accumbens , opioid , prefrontal cortex , agonist , μ opioid receptor , enkephalin , ethanol , receptor , neuroscience , biochemistry , psychology , cognition
Background: This study examined the effects of ethanol self‐administration on μ‐ and δ‐opioid receptor‐mediated G‐protein activity in specific brain regions of male Long Evans rats. Methods: Rats were trained to self‐administer ethanol by using a home‐cage modification of the sucrose substitution paradigm. After 30 to 40 days of sucrose or sucrose/15% ethanol self‐administration (20 min sessions, Monday–Friday), rats were killed for autoradiographic assays. Coronal sections of brains from sucrose and ethanol self‐administering rats were collected and processed for basal and μ‐ and δ‐stimulated [ 35 S]guanosine‐5′‐ O ‐(γ‐thio)‐triphosphate (GTPγS) binding. Sections were exposed to film and then analyzed by using computer‐assisted densitometry to determine levels of basal and agonist‐stimulated [ 35 S]GTPγS binding. Results: μ‐Opioid‐stimulated [ 35 S]GTPγS binding was decreased in the prefrontal cortex of brains from ethanol compared with sucrose self‐administering rats. μ‐Opioid‐stimulated [ 35 S]GTPγS binding was unchanged in the cingulate cortex, caudate‐putamen, nucleus accumbens, amygdala, hypothalamus, thalamus, and locus ceruleus of ethanol compared with sucrose self‐administering rats. Basal and δ‐opioid‐stimulated [ 35 S]GTPγS binding did not differ between the two groups in the prefrontal cortex or any other region analyzed. Conclusions: These data demonstrate decreased μ‐opioid‐mediated G‐protein activity in the prefrontal cortex of ethanol self‐administering rats and suggest an interaction between ethanol and μ‐opioid receptors in this region.