Heroin addiction is a chronic complex disease with a substantial genetic contribution. This study was designed to identify genetic variants that are associated with susceptibility to develop heroin addiction by analyzing 1350 variants in 130 candidate genes. All subjects had Caucasian ancestry. The sample consisted of 412 former severe heroin addicts in methadone treatment, and 184 healthy controls with no history of drug abuse. Nine variants, in six genes, showed the lowest nominal P values in the association tests (P < 0.01). These variants were in noncoding regions of the genes encoding the mu (OPRM1; rs510769 and rs3778151), kappa (OPRK1; rs6473797) and delta (OPRD1; rs2236861, rs2236857 and rs3766951) opioid receptors; the neuropeptide galanin (GAL; rs694066); the serotonin receptor subtype 3B (HTR3B; rs3758987) and the casein kinase 1 isoform epsilon (CSNK1E; rs1534891). Several haplotypes and multilocus genotype patterns showed nominally significant associations (e.g. OPRM1; P 5 0.0006 and CSNK1E; P 5 0.0007). Analysis of a combined effect of OPRM1 and OPRD1 showed that rs510769 and rs2236861 increase the risk of heroin addiction (P 5 0.0005). None of these associations remained significant after adjustment for multiple testing. This study suggests the involvement of several genes and variants in heroin addiction, which is worthy of future study. Heroin addiction is a chronic relapsing disease characterized by compulsive drug seeking, drug abuse, tolerance and physical dependence. It is treated by methadone, buprenorphine and behavioral therapy. Heroin addiction is part of group of addictions (e.g. cocaine, alcohol and nicotine) that constitute a worldwide public health crisis. The genetic contribution to vulnerability to develop heroin addiction is 40-60%, suggesting a complex inheritance mode in which multiple genes exert a small effect, along with the environment (Kendler et al. 2003;Tsuang et al. 1996Tsuang et al. , 1998. ). These include variants in the genes encoding the mu and kappa opioid receptors, dopamine receptors D2 and D4, serotonin receptor 1B, gamma-aminobutryic acid (GABA) receptor subunit gamma 2, catechol-O-methyltransferase, period circadian protein (PER3), proenkephalin, proopiomelanocortin, tryptophan hydroxylase 2 and brain-derived neurotrophic factor.To identify genetic variants that underlie heroin addiction, we performed a candidate gene case-control association study using a single nucleotide polymorphism (SNP) array that was designed by the group of D. Goldman at the National Institute of Alcohol Abuse and Alcoholism (NIAAA). This approach is based on physiological hypotheses and the genes were selected based on their function (e.g. drug receptors, neurotransmitters, transporters and drug metabolism enzymes) and related pathways (e.g. reward modulation, behavioral control, cognitive function, signal transduction and stress response). In order to maximize the power of the study, the cases were selected from the extreme margin of the specific phenotype range (e.g. severe heroin a...

Heroin addiction is a chronic complex disease with a substantial genetic contribution. This study was designed to identify gene variants associated with heroin addiction in African Americans. The emphasis was on genes involved in reward modulation, behavioral control, cognitive function, signal transduction and stress response. We have performed a case-control association analysis by screening with 1350 variants of 130 genes. The sample consisted of 202 former severe heroin addicts in methadone treatment and 167 healthy controls with no history of drug abuse. Single nucleotide polymorphism (SNP), haplotype and multi-SNP genotype pattern analyses were performed. Seventeen SNPs showed point-wise significant association with heroin addiction (nominal P < 0.01). These SNPs are from genes encoding several receptors: adrenergic (ADRA1A), arginine vasopressin (AVPR1A), cholinergic (CHRM2), dopamine (DRD1), GABA-A (GABRB3), glutamate (GRIN2A) and serotonin (HTR3A) as well as alcohol dehydrogenase (ADH7), glutamic acid decarboxylase (GAD1 and GAD2), the nucleoside transporter (SLC29A1) and diazepambinding inhibitor (DBI). The most significant result of the analyses was obtained for the GRIN2A haplotype G-A-T (rs4587976-rs1071502-rs1366076) with protective effect (P uncorrected = 9.6E-05, P corrected = 0.058). This study corroborates several reported associations with alcohol and drug addiction as well as other related disorders and extends the list of variants that may affect the development of heroin addiction. Further studies will be necessary to replicate these associations and to elucidate the roles of these variants in drug addiction vulnerability.

In this study, we investigated the effects of acute morphine administration, chronic intermittent escalating-dose morphine administration and spontaneous withdrawal from chronic morphine on mRNA levels of mu opioid receptor (MOP-r), and the opioid peptides pro-opiomelanocortin (POMC) and preprodynorphin (ppDyn) in several key brain regions of the rat, associated with drug reward and motivated behaviors: lateral hypothalamus (lat.hyp), nucleus accumbens (NAc) core, amygdala, and caudate-putamen (CPu). There was no effect on MOP-r mRNA levels in these brain regions 30 min after either a single injection of morphine (10 mg/kg, i.p.) or chronic intermittent escalating-dose morphine (from 7$5 mg/kg per day on day 1 up to 120 mg/kg per day on day 10). Activation of the stress-responsive hypothalamic-pituitary-adrenal axis by 12 h withdrawal from chronic morphine was confirmed; both POMC mRNA levels in the anterior pituitary and plasma adrenocorticotropic hormone levels were significantly elevated. Under this withdrawal-related stress condition, there was an increase in MOP-r mRNA levels in the lat.hyp, NAc core, and CPu. Recent studies have demonstrated a novel role for the lat.hyp orexin (or hypocretin) activation in both drug-related positive rewarding, and withdrawal effects. Around 50% of lat.hyp orexin neurons express MOP-r. Therefore, we also examined the levels of lat.hyp orexin mRNA, and found them increased in morphine withdrawal, whereas there was no change in levels of the lat.hyp ppDyn mRNA, a gene coexpressed with the lat.hyp orexin. Our results show that there is an increase in MOP-r gene expression in a region-specific manner during morphine withdrawal, and support the hypothesis that increased lat.hyp orexin activity plays a role in morphine-withdrawalrelated behaviors.

Adequate methadone dosing in methadone maintenance treatment (MMT) for opioid addiction is critical for therapeutic success. One of the challenges in dose determination is the inter-individual variability in dose response. Methadone metabolism is attributed primarily to cytochrome P450 enzymes CYP3A4, CYP2B6, and CYP2D6. The CYP2B6*6 allele [SNPs 785A>G (rs2279343) and 516G>T (rs3745274)] was associated with slow methadone metabolism. To explore the effects of CYP2B6*6 allele on methadone dose requirement, it was genotyped in a well-characterized sample of 74 Israeli former heroin addicts in MMT. The sample is primarily of Middle Eastern/European ancestry, based on ancestry informative markers (AIMs). Only patients with no major co-medication that may affect methadone metabolism were included. The stabilizing daily methadone dose in this sample ranges between 13-260 mg (mean 140±52 mg). The mean methadone doses required by subjects homozygous for the variant alleles of the CYP2B6 SNPs 785A>G and 516G>T (88, 96 mg, respectively) were significantly lower than those of the heterozygotes (133, 129 mg, respectively) and the non-carriers (150, 151 mg, respectively) (nominal P = 0.012, 0.048, respectively). The results remain significant after controlling for age, sex and the ABCB1 SNP 1236C>T (rs1128503), that was previously shown to be associated with high methadone dose requirement in this population (P = 0.006, 0.030, respectively). An additional 77 CYP2B6, CYP3A4 and CYP2D6 SNPs were genotyped. Of these, 24 SNPs were polymorphic and none showed significant association with methadone dose. Further studies are necessary to replicate these preliminary findings in additional subjects and other populations.

Summary Stress is a significant risk factor in the development of drug addictions and in addiction relapse susceptibility. This hypothesis-driven study was designed to determine if specific SNPs in genes related to stress response are associated with heroin and/or cocaine addiction in African Americans. The analysis included 27 genes (124 SNPs) and was performed independently for each addiction. The sample consisted of former heroin addicts in methadone maintenance treatment (n = 314), cocaine addicts (n = 281), and controls (n = 208). Fourteen SNPs showed nominally significant association with heroin addiction (p < 0.05), including the African-specific, missense SNP rs5376 (Asn334Ser) in the galanin receptor type 1 gene (GALR1) and the functional FKBP5 intronic SNP rs1360780. Thirteen SNPs showed association with cocaine addiction, including the synonymous SNPs rs237902, in the oxytocin receptor gene (OXTR), and rs5374 in GALR1. No signal remained significant after correction for multiple testing. Four additional SNPs (GALR1 rs2717162, AVP rs2282018, CRHBP rs1875999, and NR3C2 rs1040288) were associated with both addictions and may indicate common liability. The study provides preliminary evidence for novel association of variants in several stress related genes with heroin and/or cocaine addictions and may enhance the understanding of the interaction between stress and addictions.

Rationale Although non-medical use of oxycodone continues to be a growing problem in the United States, there are no animal studies examining the effects of long term oxycodone self administration (SA). Objectives The current study was designed to examine chronic oxycodone SA by mice (14 days), in novel extended (4 hours) SA sessions and its effect on selective striatal neurotransmitter receptor mRNA expression. Methods Adult male C57/BL6J mice were either allowed to self administer oxycodone (0.25 mg/kg/infusion, FR1) or served as yoked-saline controls in an extended access paradigm. Mice self administered oxycodone for 4 hours/day for 14 consecutive days. Comparison groups with 14-days exposure to 1-hour SA sessions were also studied. Within one hour of the last extended SA session, mice were sacrificed, dorsal striatum was isolated and selective neurotransmitter receptor mRNA levels were examined. Results The oxycodone groups poked the active hole significantly more times than the yoked controls. The number of nose pokes at the active hole rose over the 14 days in the oxycodone group with extended access. The expression of thirteen neurotransmitter receptor mRNAs was significantly altered in the dorsal striatum, including the GABA A receptor beta 2 subunit (Gabrb2) showing experiment-wise significant decrease, as a result of extended oxycodone SA. Conclusion C57BL/6J mice escalated the amount of oxycodone self administered across 14 consecutive daily extended sessions, but not 1-hour sessions. Decreases in Gabrb2 mRNA levels may underlie escalation of oxycodone intake in the extended access SA sessions.

Summary Background Stress is a critical risk factor affecting both the development of and the relapse to drug addictions. Drug addictions are caused by genetic, environmental and drug-induced factors. The objective of this hypothesis-driven association study was to determine if genetic variants in stress-related genes are associated with heroin addiction. Methods 112 selected genetic variants in 26 stress-related genes were genotyped in 852 case subjects and 238 controls of predominantly European ancestry. The case subjects are former heroin addicts with a history of at least one year of daily multiple uses of heroin, treated at a methadone maintenance treatment program (MMTP). The two most promising SNPs were subsequently tested in an African-American sample comprising of 314 cases and 208 control individuals. Results Nineteen single nucleotide polymorphisms (SNPs) in 9 genes (AVP, CRHR1, CRHR2, FKBP5, NR3C2, AVPR1A, GAL, GLRA1, and NPY1R) showed nominally significant association with heroin addiction. The associations of two FKBP5 SNPs that are part of one haplotype block, rs1360780 (intron 2) and rs3800373 (the 3' untranslated region), remained significant after correction for multiple testing (Pcorrected =0.03; OR = 2.35, Pcorrected = 0.0018; OR = 2.85, respectively). The two SNPs also showed nominally significant association (P <0.05) with heroin addiction in an independent African-American cohort. FKBP5 is a co-chaperone that regulates glucocorticoid sensitivity. These FKBP5 SNPs were previously associated with diverse affective disorders and showed functional differences in gene expression and stress response. This study also supports our and others’ previous reports of association of the GAL SNP rs694066 and the AVPR1A SNPs rs11174811, rs1587097 and rs10784339 with heroin and general drug addiction, respectively. Conclusions This study suggests that variations in the FKBP5 gene contribute to the development of opiate addiction by modulating the stress response. These findings may enhance the understanding of the interaction between stress and heroin addiction.

Alterations in expression of a cannabinoid receptor (CNR1, CB1), and of fatty acid amide hydrolase (FAAH) that degrades endogenous ligands of CB1, may contribute to the development of addiction. The 385C>A in the FAAH gene and six polymorphisms of CNR1 were genotyped in former heroin addicts and control subjects (247 Caucasians, 161 Hispanics, 179 African Americans and 19 Asians). In Caucasians, long repeats (≥14) of 18087–18131 (TAA)8–17 were associated with heroin addiction (P = 0.0102). Across three ethnicities combined, a highly significant association of long repeats with heroin addiction was found (z = 3.322, P = 0.0009). Point-wise significant associations of allele 1359A (P= 0.006) and genotype 1359AA (P= 0.034) with protection from heroin addiction were found in Caucasians. Also in Caucasians, the genotype pattern, 1359G>A and −6274A>T, was significantly associated with heroin addiction experiment wise (P= 0.0244). No association of FAAH 385C>A with heroin addiction was found in any group studied.