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α 2A ‐Adrenergic receptor polymorphisms and mRNA expression levels are associated with delay discounting in cocaine users
Author(s) -
Havranek Michael M.,
Hulka Lea M.,
Tasiudi Eve,
Eisenegger Christoph,
Vonmoos Matthias,
Preller Katrin H.,
Mössner Rainald,
Baumgartner Markus R.,
Seifritz Erich,
Grünblatt Edna,
Quednow Boris B.
Publication year - 2017
Publication title -
addiction biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.445
H-Index - 78
eISSN - 1369-1600
pISSN - 1355-6215
DOI - 10.1111/adb.12324
Subject(s) - discounting , delay discounting , receptor , adrenergic , medicine , endocrinology , biology , psychology , pharmacology , economics , finance
Cocaine users characteristically display preferences for smaller immediate rewards over larger delayed rewards, and this delay discounting (DD) has been proposed as an endophenotype of cocaine addiction. Recent evidence suggests that the norepinephrine system and more specifically the α 2A ‐adrenergic receptor ( ADRA2A ) are impacted by chronic cocaine use while also being potentially involved in the neural mechanisms underlying DD. Hence, we investigated the effects of ADRA2A polymorphisms and ADRA2A mRNA expression levels on DD of cocaine users and stimulant‐naïve controls. Two hundred and twenty‐three participants (129 cocaine users and 94 stimulant‐naïve healthy controls) completed a computerized DD paradigm and were genotyped for three single nucleotide polymorphisms (SNPs; rs1800544, rs521674 and rs602618) in the ADRA2A gene, while their peripheral ADRA2A mRNA expression was quantified in whole blood samples. The three SNPs were in near‐perfect linkage disequilibrium. Accordingly, significant group*genotype interactions were found for all three ADRA2A variants revealing steeper DD in cocaine users (but not in controls) carrying the G‐allele of SNP rs1800544, the T‐allele of rs521674 and the C‐allele of rs602618. Similarly, high ADRA2A mRNA expression levels were significantly associated with a reduced tendency to choose smaller more immediate rewards (over larger delayed rewards) in cocaine users but not in controls. As the relationship between DD and cocaine use was moderated by ADRA2A SNPs and by peripheral ADRA2A gene expression, we propose that the norepinephrine system is involved in DD deficits observed in cocaine using individuals. Consequently, pharmacological compounds targeting ADRA2A s might be considered for the symptom‐specific treatment of delay aversion in stimulant addiction.