Naltrexone selectively elevates GABAergic neuroactive steroid levels in heavy drinkers with the Asp40 allele of the OPRM1 gene: a pilot investigation.
BACKGROUND
Preclinical studies have implicated GABAergic neurosteroids in behavioral responses to alcohol. Naltrexone is thought to blunt the reinforcing effects of alcohol, and a few studies have found that the effects of naltrexone are moderated by the Asn40Asp polymorphisms of the OPRM1 gene. The present study seeks to integrate these lines of research by testing (i) the moderating role of the functional Asn40Asp polymorphism of the OPRM1 gene on naltrexone-induced alternations in GABAergic neurosteroid levels, namely (3alpha,5alpha)-3-hydroxypregnan-20-one (allopregnanolone, ALLO); and (ii) the combined effects of naltrexone or genotype with alcohol administration on neurosteroid levels in a sample of at-risk drinkers.


METHODS
Participants were 32 (9 females) nontreatment-seeking heavy drinkers who completed a placebo-controlled laboratory study of naltrexone (50 mg/d for 3 days) and provided complete sets of serum samples for ALLO assays before and after alcohol administration under both naltrexone and placebo conditions.


RESULTS
Naltrexone treatment raised ALLO levels among carriers of the Asp40 allele, but not homozygotes for the Asn40 allele. The Asn40Asp polymorphism did not moderate effects of naltrexone on cortisol levels. Ethanol infusion modestly reduced ALLO levels in all subjects, independent of genotype or naltrexone exposure.


CONCLUSIONS
Naltrexone increased ALLO levels among individuals with the Asn40Asp allele suggesting a potential neurosteroid contribution to the neuropharmacological effects of naltrexone among Asp40 carriers.
Department of Psychology, University of California Los Angeles, Los Angeles, California 90095-1563, USA. lararay@psych.ucla.edu
Lara A
LA
Ray
Kent E
KE
Hutchison
James R
JR
Ashenhurst
A Leslie
AL
Morrow
D000328:Adult; D000428:Alcohol Drinking / Q000097:blood / Q000188:drug therapy / Q000235:genetics; D000437:Alcoholism / Q000097:blood* / Q000188:drug therapy / Q000235:genetics*; D000483:Alleles; D019943:Amino Acid Substitution / Q000235:genetics; D001224:Aspartic Acid / Q000235:genetics; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009271:Naltrexone / Q000494:pharmacology*; D010865:Pilot Projects; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011280:Pregnanolone / Q000097:blood*; D017450:Receptors, Opioid, mu / Q000235:genetics*; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000097:blood
C485764:OPRM1 protein, human; D017450:Receptors, Opioid, mu; D001224:Aspartic Acid; D005680:gamma-Aminobutyric Acid; D009271:Naltrexone; D011280:Pregnanolone