Mouse model of the OPRM1 (A118G) polymorphism: differential heroin self-administration behavior compared with wild-type mice.

Mu-opioid receptors (MOPRs) are the target of heroin and other prescription opioids, which are currently responsible for massive addiction morbidity in the US. The gene coding for the human MOPR (OPRM1) has an important functional single nucleotide polymorphism (SNP), A118G. The OPRM1 A118G genotype results in substantially increased risk of heroin addiction in humans; however, the neurobiological mechanism for this increased risk is not fully understood. This study examined heroin self-administration (SA) behavior in A112G (G/G) mice, harboring a functionally equivalent SNP in Oprm1 with a similar amino acid substitution, in extended (4 h) SA sessions. Adult male and female G/G mice and 'wild-type' litter mates (A/A) were allowed to self-administer heroin (0.25 mg/kg/unit dose, FR1 with a nose poke response) for 4 h/day, for 10 consecutive days. Half of the mice then continued in a heroin dose-response study, while extinction from heroin SA was studied in the other half. In vivo microdialysis was used to measure acute heroin-induced increases of striatal dopamine in the GG vs AA genotypes. Male and female G/G mice responded for heroin significantly more (and thus had greater intake) than A/A mice, in the initial 10 days of heroin SA, and in the subsequent dose-response study. There were no significant differences in extinction of SA between the A/A and G/G mice. Heroin-induced increases in striatal dopamine levels are higher in the GG mice than in the AA mice. Both male and female G/G mice self-administered more heroin than did A/A mice over a 10-day period, possibly because of the greater increases of heroin-induced striatal dopamine in the GG mice. Furthermore, G/G male mice escalated the amount of heroin self-administration across 10 extended-access sessions more than A/A male mice did. These are the first studies to examine the acquisition of heroin SA in this mouse model. These studies may lead to a better understanding of the neurobiological and behavioral mechanisms that underlie greater risk of heroin addiction in carriers of the A118G SNP.

Neurocognitive and neuroinflammatory correlates of PDYN and OPRK1 mRNA expression in the anterior cingulate in postmortem brain of HIV-infected subjects.

Chronic inflammation may contribute to neuropsychological impairments in individuals with HIV, and modulation of this inflammatory response by opiate receptor ligands is important in light of the prevalence of drug use in HIV populations. Exogenous MOR and KOR agonists have differential effects on central nervous system (CNS) immunity and, while some data suggest KOR agonists are immunosuppressive, the KOR agonist dynorphin has been shown to stimulate human monocyte chemotaxis. In this study, we examined mRNA levels of endogenous opioid receptors OPRK1 and OPRM1, prodynorphin (PDYN), macrophage scavenger receptor CD163, and microglia/macrophage marker CD68 in the caudate and anterior cingulate of postmortem brains from HIV-positive and HIV-negative subjects. Brain tissues of HIV-infected (n = 24) and control subjects (n = 15) were obtained from the Manhattan HIV Brain Bank. Quantification of the gene mRNA was performed using SYBR Green RT-PCR. CD68 and CD163 were increased in HIV-positive (HIV+) compared to HIV-negative (HIV-) individuals in both brain regions. There were higher OPRK1 (P <0.005), and lower PDYN mRNA (P <0.005) levels in the anterior cingulate of HIV+ compared to HIV- subjects. This difference between the clinical groups was not found in the caudate. There was no difference in the levels of OPRM1 mRNA between HIV+ and HIV- subjects. Using linear regression analysis, we examined the relationship of OPRK1 and PDYN mRNA levels in the HIV+ subjects with seven cognitive domain T scores of a neuropsychological test battery. Within the HIV+ subjects, there was a positive correlation between anterior cingulate PDYN mRNA levels and better T-scores in the motor domain. Within the HIV+ subjects there were also positive correlations of both OPRK1 and PDYN mRNA levels with the anti-inflammatory marker CD163, but not with proinflammatory CD68 levels. In this setting, decreased PDYN mRNA may reflect a homeostatic mechanism to reduce monocyte migration, accompanied by compensatory increases in the cognate receptor (KOR) to dampen pro-inflammatory responses. It is possible that enhanced neuroprotection and better motor performance are associated with higher levels of dynorphin and the recruitment of neuroprotective CD163-positive macrophages. Further studies are needed to test this hypothesis.

Extended access oxycodone self-administration and neurotransmitter receptor gene expression in the dorsal striatum of adult C57BL/6 J mice.

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 h) 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 h/day for 14 consecutive days. Comparison groups with 14-days exposure to 1-h SA sessions were also studied. Within 1 h 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 13 neurotransmitter receptor mRNAs was significantly altered in the dorsal striatum, including the gamma-aminobutyric acid (GABA) A receptor beta 2 subunit (Gabrb2) showing experiment-wise significant decrease, as a result of extended oxycodone SA. CONCLUSION: C57BL/6 J mice escalated the amount of oxycodone self-administered across 14 consecutive daily extended sessions, but not 1-h sessions. Decreases in Gabrb2 mRNA levels may underlie escalation of oxycodone intake in the extended access SA sessions.

Genetic diversity and linkage disequilibrium in the chemokine receptor CCR2-CCR5 region among individuals and populations.

BACKGROUND: Chemokine receptors CCR2 and CCR5 play a key role in immune and inflammatory responses and have been associated with several diseases, including AIDS. In order to comprehend health disparities it is important to understand the nature of genetic variation in specific genes of interest in different populations. Current studies of the CCR2 and CCR5 receptor genes are primarily focused on the CCR5-Δ32, and CCR2-V64I SNPs. METHODS: Sanger sequencing was used to sequence the regions containing 16 SNPs in the adjacent CCR2 and CCR5 genes (including CCR5-Δ32, and CCR2-V64I) in 249 subjects of African, European and Hispanic ancestry. Linkage disequilibrium (LD) and haplotypes were determined using Haploview. RESULTS: The data revealed large differences in allele frequencies of several SNPs and LD patterns among the ethnic groups, including SNPs that were restricted to Africans or Europeans. Seven known CCR5 haplotypes and six novel CCR2 haplotypes were identified. A rare case of an HIV+ subject with the CCR5-Δ32/Δ32 was identified. CONCLUSIONS: These data demonstrate a LD between CCR2 and CCR5 at several loci and provide new information about CCR2 that contributes to our understanding of its population-specific genetic variability. The data indicate that in addition to CCR5-Δ32 and CCR2-V64I, other SNPs and haplotypes may be important genetic determinants of disease and should be investigated.

Oxycodone-induced conditioned place preference and sensitization of locomotor activity in adolescent and adult mice.

Nonmedical use of the prescription opioid oxycodone has become a major public health problem in the United States, with special concern for adolescents. Although adults and adolescents have different sensitivities for drugs, little is known about the rewarding effects of oxycodone in adolescents compared to adults, even in rodent models. Here, we investigate sensitivity to oxycodone by the conditioned place preference assay of conditioned reward, and effect on the locomotor activity in adolescent (4 weeks old) and adult (10 weeks old) C57BL/6J mice. Mice of both ages were trained with multiple doses of oxycodone (0, 0.3, 1, and 3 mg/kg) and showed conditioned preference in a dose-dependent manner. The adult mice developed conditioned preference to the lowest dose tested (0.3 mg/kg), but adolescent mice did not. Dose-dependent oxycodone-induced increases in locomotor activity were observed across the conditioning session. Interestingly, adolescent mice developed greater sensitization to the locomotor-activating effects of oxycodone than adult mice. Thus differences in sensitivity to oxycodone, such as the lower initial sensitivity for conditioned preference but greater locomotor sensitization in adolescent mice, may indicate contributing factors in oxycodone abuse and later addiction in human adolescents.

Suppression of hypothalamic-pituitary-adrenal axis by acute heroin challenge in rats during acute and chronic withdrawal from chronic heroin administration.

It is known that heroin dependence and withdrawal are associated with changes in the hypothalamic-pituitary-adrenal (HPA) axis. The objective of these studies in rats was to systematically investigate the level of HPA activity and response to a heroin challenge at two time points during heroin withdrawal, and to characterize the expression of associated stress-related genes 30 min after each heroin challenge. Rats received chronic (10-day) intermittent escalating-dose heroin administration (3 × 2.5 mg/kg/day on day 1; 3 × 20 mg/kg/day by day 10). Hormonal and neurochemical assessments were performed in acute (12 h after last heroin injection) and chronic (10 days after the last injection) withdrawal. Both plasma ACTH and corticosterone levels were elevated during acute withdrawal, and heroin challenge at 20 mg/kg (the last dose of chronic escalation) at this time point attenuated this HPA hyperactivity. During chronic withdrawal, HPA hormonal levels returned to baseline, but heroin challenge at 5 mg/kg decreased ACTH levels. In contrast, this dose of heroin challenge stimulated the HPA axis in heroin naïve rats. In the anterior pituitary, pro-opiomelanocortin (POMC) mRNA levels were increased during acute withdrawal and retuned to control levels after chronic withdrawal. In the medial hypothalamus, however, the POMC mRNA levels were decreased during acute withdrawal, and increased after chronic withdrawal. Our results suggest a long-lasting change in HPA abnormal responsivity during chronic heroin withdrawal.

Polymorphisms of the kappa opioid receptor and prodynorphin genes: HIV risk and HIV natural history.

OBJECTIVE: Studies indicate cross-desensitization between opioid receptors (eg, kappa opioid receptor, OPRK1) and chemokine receptors (eg, CXCR4) involved in HIV infection. Whether gene variants of OPRK1 and its ligand, prodynorphin (PDYN), influence the outcome of HIV therapy was tested. METHODS: Three study points, admission to the Women's Interagency HIV Study, initiation of highly active antiretroviral therapy (HAART), and the most recent visit, were chosen for analysis as crucial events in the clinical history of the HIV patients. Regression analyses of 17 variants of OPRK1 and 11 variants of PDYN with change of viral load (VL) and CD4 count between admission and initiation of HAART and initiation of HAART to the most recent visit to Women's Interagency HIV Study were performed in 598 HIV+ subjects, including African Americans, Hispanics, and Whites. Association with HIV status was done in 1009 subjects. RESULTS: Before HAART, greater VL decline (improvement) in carriers of PDYN IVS3+189C>T and greater increase of CD4 count (improvement) in carriers of OPRK -72C>T were found in African Americans. Also, greater increase of CD4 count in carriers of OPRK1 IVS2+7886A>G and greater decline of CD4 count (deterioration) in carriers of OPRK1 -1205G>A were found in Whites. After HAART, greater decline of VL in carriers of OPRK1 IVS2+2225G>A and greater increase of VL in carriers of OPRK1 IVS2+10658G>T and IVS2+10963A>G were found in Whites. Also, a lesser increase of CD4 count was found in Hispanic carriers of OPRK1 IVS2+2225G>A. CONCLUSIONS: OPRK1 and PDYN polymorphisms may alter severity of HIV infection and response to treatment.

Expression of ephrin receptors and ligands in postmortem brains of HIV-infected subjects with and without cognitive impairment.

Despite the successes of combination antiretroviral therapy, HIV-associated neurocognitive disorders persist in many infected individuals. Earlier studies showed that neurocognitive impairment was associated with glutamate toxicity and synaptodendritic damage. We examined alterations in expression of four ephrin genes that are involved in synapse formation and recruitment of glutamate receptors to synapses, in the caudate and anterior cingulate in postmortem brain of cognitively characterized HIV-infected subjects, along with expression of neuronal and astroglial/macroglial markers. Postmortem tissues of HIV-infected and control subjects were obtained from the Manhattan HIV Brain Bank. HIV-infected subjects underwent neurocognitive assessment prior to death. Quantification of mRNA of genes of chemokine receptors and chemokines (CCR5, CXCR4, CCL2), astroglial/microglial markers (GFAP, CD163, CD68), the neuronal marker SNAP25, ephrin receptors EPHA4 and EPHB2, and ephrin ligands EFNB1 and EFNB2 was performed using SYBR Green RT-PCR. Proinflammatory chemokine and glial/macrophage mRNA levels in both regions were significantly greater in HIV+ than in HIV- subjects. Levels of EPHA4 and EFNB2 mRNA in the caudate, and EPHB2 mRNA in anterior cingulate were significantly lower in HIV+ subjects (p < 0.002, p < 0.02, p < 0.05, respectively). These transcripts also showed correlations with immune status and cognitive function within the HIV-infected group. Decreased levels of EFNB2 mRNA in the caudate correlated with lower CD4 counts (P < 0.05). Cognitive associations were limited to the cingulate, where decreased levels of EPHB2 mRNA were associated with better global cognitive status. Decreased cingulate expression of EPHB2 may represent a compensatory mechanism minimizing excitotoxic injury in the face of chronic inflammation.

Voluntary alcohol drinking enhances proopiomelanocortin gene expression in nucleus accumbens shell and hypothalamus of Sardinian alcohol-preferring rats.

BACKGROUND: Evidence obtained in humans and rodents indicates that beta-endorphin (encoded by the proopiomelanocortin [POMC] gene) is critical in the regulation of alcohol drinking behavior. However, the alcohol effect on POMC gene expression has not been studied in rodent mesolimbic regions, such as the nucleus accumbens (NAc). METHODS: In this study, we first utilized POMC-enhanced green fluorescent protein (EGFP) transgenic mice to visualize POMC neurons and found that POMC-EGFP cells were modestly distributed throughout the NAc shell and core, in addition to the hypothalamic arcuate nucleus. POMC mRNA expression in the NAc of mice and rats was confirmed using reverse transcriptase-polymerase chain reaction and solution hybridization assays. We then investigated whether there are genetically determined differences in basal mRNA levels of POMC and mu opioid receptor (MOP-r) between selectively bred Sardinian alcohol-preferring (sP) and nonpreferring (sNP) rats, and whether these mRNA levels are altered in sP rats after alcohol drinking (10%, unlimited access) for 17 days. RESULTS: Alcohol-naïve sP rats had higher basal POMC mRNA levels than sNP rats only in hypothalamus. Alcohol drinking increased POMC mRNA levels in both the NAc shell (by 100%) and the hypothalamus (by 50%) of sP rats. Although sP rats had lower basal levels of MOP-r mRNA and GTPγS binding in NAc shell than sNP rats, voluntary alcohol consumption had no effect on MOP-r mRNA levels in the NAc shell. CONCLUSIONS: Our results define the distribution of POMC-expressing neurons in the NAc of mice and rats. Higher POMC expression at basal levels in sP rats (genetically determined), along with increases after drinking (alcohol-induced) in the NAc shell and hypothalamus, suggests that the POMC systems play a role in high alcohol preference and consumption.

Tolerance and sensitization to chronic escalating dose heroin following extended withdrawal in Fischer rats: possible role of mu-opioid receptors.

RATIONALE/OBJECTIVES: Heroin addiction is characterized by recurrent cycles of drug use, abstinence, and relapse. It is likely that neurobiological changes during chronic heroin exposure persist across withdrawal and impact behavioral responses to re-exposure. We hypothesized that, after extended withdrawal, heroin-withdrawn rats would express behavioral tolerance and/or sensitization in response to heroin re-exposure and that these responses might be associated with altered mu-opioid receptor (MOPr) activity. METHODS: Male Fischer rats were exposed chronically to escalating doses of heroin (7.5-75 mg/kg/day), experienced acute spontaneous withdrawal and extended (10-day) abstinence, and were re-exposed chronically to heroin. Homecage behaviors and locomotor activity in response to heroin, as well as somatic withdrawal signs, were recorded. Separate groups of rats were sacrificed after extended abstinence and MOPr expression and G-protein coupling were analyzed using [(3)H]DAMGO and [(35)S]GTPγS assays. RESULTS: The depth of behavioral stupor was lower during the initial days of heroin re-exposure compared to the initial days of the first exposure period. Behavioral responses (e.g., stereotypy) and locomotion were elevated in response to heroin re-exposure at low doses. Rats conditioned for heroin place preference during the chronic re-exposure period expressed heroin preference during acute withdrawal; this preference was stronger than rats conditioned during chronic heroin exposure that followed chronic saline and injection-free periods. Extended withdrawal was associated with increased MOPr expression in the caudate-putamen and frontal and cingulate cortices. No changes in G-protein coupling were identified. CONCLUSIONS: Aspects of tolerance/sensitization to heroin are present even after extended abstinence and may be associated with altered MOPr density.

Chronic escalating cocaine exposure, abstinence/withdrawal, and chronic re-exposure: effects on striatal dopamine and opioid systems in C57BL/6J mice.

Cocaine addiction is a chronic relapsing disease with periods of chronic escalating self-exposure, separated by periods of abstinence/withdrawal of varying duration. Few studies compare such cycles in preclinical models. This study models an "addiction-like cycle" in mice to determine neurochemical/molecular alterations that underlie the chronic, relapsing nature of this disease. Groups of male C57BL/6J mice received acute cocaine exposure (14-day saline/14-day withdrawal/13-day saline + 1-day cocaine), chronic cocaine exposure (14 day cocaine) or chronic re-exposure (14-day cocaine/14-day withdrawal/14-day cocaine). Escalating-dose binge cocaine (15-30 mg/kg/injection × 3/day, i.p. at hourly intervals) or saline (14-day saline) was administered, modeling initial exposure. In "re-exposure" groups, after a 14-day injection-free period (modeling abstinence/withdrawal), mice that had received cocaine were re-injected with 14-day escalating-dose binge cocaine, whereas controls received saline. Microdialysis was conducted on the 14th day of exposure or re-exposure to determine striatal dopamine content. Messenger RNA levels of preprodynorphin (Pdyn), dopamine D1 (Drd1) and D2 (Drd2) in the caudate putamen were determined by real-time PCR. Basal striatal dopamine levels were lower in mice after 14-day escalating exposure or re-exposure than in those in the acute cocaine group and controls. Pdyn mRNA levels were higher in the cocaine groups than in controls. Long-term adaptation was observed across the stages of this addiction-like cycle, in that the effects of cocaine on dopamine levels were increased after re-exposure compared to exposure. Changes in striatal dopaminergic responses across chronic escalating cocaine exposure and re-exposure are a central feature of the neurobiology of relapsing addictive states.

Mu-opioid receptor A118G polymorphism in healthy volunteers affects hypothalamic-pituitary-adrenal axis adrenocorticotropic hormone stress response to metyrapone.

The mu-opioid receptor encoded by the gene OPRM1 plays a primary role in opiate, alcohol, cocaine and nicotine addiction. Studies using opioid antagonists demonstrate that the mu-opioid receptor (MOP-r) also mediates the hypothalamic-pituitary-adrenal (HPA) axis stress response. A common polymorphism in exon one of the MOP-r gene, A118G, has been shown to significantly alter receptor function and MOP-r gene expression; therefore, this variant likely affects HPA-axis responsivity. In the current study, we have investigated whether the presence of the 118AG variant genotype affects HPA axis responsivity to the stressor metyrapone, which transiently blocks glucocorticoid production in the adrenal cortex. Forty-eight normal and healthy volunteers (32 men, 16 women) were studied, among whom nine men and seven women had the 118AG genotype. The 118G allele blunted the adrenocorticotropic hormone (ACTH) response to metyrapone. Although there was no difference in basal levels of ACTH, subjects with the 118AG genotype had a more modest rise and resultant significantly lower ACTH levels than those with the prototype 118AA at the 8-hour time point (P < 0.02). We found no significant difference between genders. These findings suggest a relatively greater tonic inhibition at hypothalamic-pituitary sites through the mu-opioid receptor and relatively less cyclical glucocorticoid inhibition in subjects with the 118G allele.

Effects of withdrawal from chronic escalating-dose binge cocaine on conditioned place preference to cocaine and striatal preproenkephalin mRNA in C57BL/6J mice.

UNLABELLED: Relapse is a serious problem for the effective treatment of cocaine addiction. RATIONALE: Examining cocaine re-exposure-induced behavioral and neurobiological alterations following chronic escalating-dose binge cocaine administration and withdrawal may provide insight into the neurobiological basis of cocaine relapse. OBJECTIVES: Our goal was to determine how exposure to chronic escalating-dose cocaine affects development of subsequent cocaine-induced conditioned place preference (CPP) and changes in endogenous opioid systems. METHODS: Mice were injected with either escalating-dose binge cocaine (15-30 mg/kg/injection × 3/day) or saline for 14-days and conditioned with 15 mg/kg of cocaine or saline (once per day for 10-days), starting either 1 or 14-days after the last day of binge injections. RESULTS: Mice exposed to chronic escalating cocaine did not develop CPP to cocaine when conditioning commenced on the first day of withdrawal (CPP test on day 10 of withdrawal). By contrast, mice did develop CPP to cocaine when conditioning started on the 14th day of withdrawal (CPP test on day 24 of withdrawal). Furthermore, preproenkephalin (Penk) mRNA levels in caudate putamen were significantly higher in mice that received 14-day withdrawal from escalating-dose binge cocaine before the CPP procedure (tested 24 days post-binge) than those that received 1-day withdrawal (tested 10 days post-binge). CONCLUSIONS: The rewarding effect of cocaine was blunted in early withdrawal from chronic escalating exposure, but recovered in more prolonged withdrawal. Time-dependent elevations in Penk mRNA levels may be part of the underlying mechanisms of this effect.

Association of polymorphisms of the mu opioid receptor gene with the severity of HIV infection and response to HIV treatment.

BACKGROUND: Mu opioid receptor (OPRM1) ligands may alter expression of chemokines and chemokine receptors involved in penetration of human immunodeficiency virus (HIV) type 1 into the cell. We suggest that OPRM1 variants may affect the pathophysiology of HIV infection. METHODS: DNA samples from 1031 eligible African Americans, Hispanics, and whites from the Women's Interagency HIV Study (WIHS) who were alive as of April 2006 were analyzed. We performed regression analysis of association of 18 OPRM1 variants with a change of viral load and CD4 cell count during 2 periods: between admission to WIHS and the start of highly active antiretroviral therapy (HAART) (interval X) and between the start of HAART and the most recent WIHS visit (interval Y), and examined the association of these variants with HIV status. RESULTS: Regardless of genotype, a significant decrease in viral load during interval X was found for each ethnicity. Whites with allele G of the functional polymorphism 118A > G (reference sequence rs1799971) showed a smaller decrease in viral load; those bearing minor alleles IVS1 + 1050A, IVS1 + 14123A, and IVS2 + 31A showed a larger decrease in viral load over interval X (0.01 < P < .05). Hispanics with the same alleles showed a greater increase in CD4 cell count over interval Y (0.01 < P < .05). We found an association between OPRM1 variants and HIV status in African Americans and whites. CONCLUSIONS: OPRM1 polymorphisms may alter the severity of HIV infection before and after HAART.

Former heroin addicts with or without a history of cocaine dependence are more impulsive than controls.

BACKGROUND: Personality traits such as impulsivity and sensation seeking may contribute to the initiation and maintenance of illicit drug use. Since studies have reported higher impulsivity and sensation seeking traits in cocaine dependent subjects, we were interested in determining whether former heroin addicts in methadone pharmacotherapy with comorbid cocaine addiction have greater impulsivity than those without. METHODS: Instruments to assess impulsivity (Barratt Impulsiveness Scale version 11) and sensation seeking (Sensation Seeking Scale version V) were administered to former severe heroin addicts meeting Federal criteria for methadone maintenance pharmacotherapy with (n = 71) or without cocaine dependence (n = 31) and to 145 normal healthy (non-methadone-maintained) volunteers. RESULTS: The methadone-maintained without cocaine dependence and the methadone-maintained with cocaine dependence groups, both scored higher than did the normal volunteer group on the Barratt Impulsiveness Scale total score (p<0.001). On the Barratt Impulsiveness Scale Attentional, Nonplanning, and Motor subscales, the methadone-maintained and methadone-maintained with cocaine dependence groups scored higher than did normal volunteers with no history of drug abuse or dependence (p<0.001). There was no difference among groups on total score or any subscale of the Sensation Seeking Scale. However, males in all groups overall scored higher than did females on Disinhibition and Thrill and Adventure seeking subscales of the Sensation Seeking Scale version V (p<0.001). CONCLUSIONS: This study demonstrates higher impulsivity in former severe heroin addicts meeting criteria for or currently in stable methadone maintenance pharmacotherapy, irrespective of a positive or negative history of cocaine dependence.

A C17T polymorphism in the mu opiate receptor is associated with quantitative measures of drug use in African American women.

Previous studies of the association of the C17T polymorphism of the mu opiate receptor gene with substance dependence compared cases with substance dependence to controls and usually found no significant association. However, the studies were limited by small sample size-no study had more than 12 subjects with the TT genotype, a genotype that is rare in white and Asian subjects. Moreover, drug use is not dichotomous but follows a spectrum from non-use to modest, intermittent use, to use several times daily. We asked whether the Kreek-McHugh-Schluger-Kellogg (KMSK) scales for alcohol, cocaine, opiates and tobacco that quantify substance use during the time of a subject's maximal use might be more sensitive measures than dichotomous outcomes. We administered the KMSK scales and completed C17T genotyping on 1009 human immunodeficiency virus (HIV)-infected and 469 HIV-uninfected women in The Women's Interagency HIV Study, an ongoing study of HIV in women. Forty-two of the 697 African American, 1 of the 182 Hispanic and none of the 161 white women had the TT genotype. KMSK cocaine, alcohol and tobacco scores were significantly higher in the African American women with the TT genotype (P = 0.008, 0.0001, and 0.006, respectively), but opiate scores were not. Ordinal regression models controlling for HIV serostatus, age, education, and income had odds ratios for the TT genotype for predicting alcohol, tobacco, cocaine and opiates scores of 2.1 (P = 0.02), 2.4 (P = 0.0004), 2.0 (P = 0.03) and 1.9 (P = 0.07). We conclude that the TT genotype of OPRM1 may increase the risk of substance use and abuse.

Effects of hepatitis C and HIV on cognition in women: data from the Women's Interagency HIV Study.

OBJECTIVE: To compare neuropsychological scores in women infected with HIV, women infected with both HIV and hepatitis C, and uninfected subjects. BACKGROUND: Some, but not all, studies have demonstrated that dual infection with Hepatitis C virus (HCV) and HIV has worse effects on cognition than infection with HIV alone. DESIGN/METHODS: The Women's Interagency HIV Study is an ongoing prospective study of the natural history of HIV in women where participants are reevaluated every 6 months. In a cross-sectional analysis, we evaluated the effects of active HIV and HCV infections on scores on symbol-digit modalities test, the Stroop interference test, and trails A and B after controlling for age, ethnicity, education, depression, liver disease, and current or past substance abuse. RESULTS: Data were available for 1338 women-17.8 % had detectable hepatitis C virus and 67% were HIV seropositive. In fully adjusted general linear models, HCV viremia was not associated with scores on any of the cognitive tests. CONCLUSIONS: In this large sample of women, active HCV infection was not associated with scores on a small battery of neuropsychological tests.

Dose escalation and dose preference in extended-access heroin self-administration in Lewis and Fischer rats.

RATIONALE: A genetic component may be involved in different stages of the progression of drug addiction. Heroin users escalate unit doses and frequency of self-administration events over time. Rats that self-administer drugs of abuse over extended sessions escalate the amount of drug infused over days. OBJECTIVES: Using a recently developed model of extended-access self-administration allowing for subject-controlled dose escalation of the unit dose, thus potentially escalating the unit dose and number of infusions, we compared for the first time two genetically different inbred rat strains, Fischer and Lewis. METHODS: Extended (18 h/day) self-administration lasted for 14 days. Rats had access to two active levers associated with two different unit doses of heroin. If a rat showed preference for the higher unit dose, then the available doses were escalated in the following session. Four heroin unit doses were available (20, 50, 125, 250 µg/kg per infusion). RESULTS: Fischer rats did not escalate the unit dose of heroin self-administered; daily amount of heroin administered remained low, with a mean daily intake of 1.27 ± 0.22 mg/kg per session. In marked contrast, Lewis rats escalated the total daily amount of heroin self-administered from 3.94 ± 0.82 mg/kg on day 1 to 8.95 ± 2.2 mg/kg on day 14; almost half of the subjects preferred a higher heroin dose than Fischer rats. CONCLUSION: These data are consistent with the hypothesis that Lewis rats are prone to opiate taking and escalation, and are in agreement with our previous data obtained with cocaine.

Measuring the incentive value of escalating doses of heroin in heroin-dependent Fischer rats during acute spontaneous withdrawal.

RATIONALE/OBJECTIVES: Although continued heroin use and relapse are thought to be motivated, in part, by the positive incentive-motivational value attributed to heroin, little is understood about heroin's incentive value during the relapse-prone state of withdrawal. This study uses place preference to measure the incentive value attributed to escalating-dose heroin in the context of heroin dependence. METHODS: Male Fischer rats were exposed chronically to escalating doses of heroin in the homecage and during place preference conditioning sessions. Conditioned preference for the context paired with escalating-dose heroin was tested after homecage exposure was discontinued and rats entered acute spontaneous withdrawal. Individuals' behavioral and locomotor responses to heroin and somatic withdrawal signs were recorded. RESULTS: Conditioned preference for the heroin-paired context was strong in rats that received chronic homecage exposure to escalating-dose heroin and were tested in acute withdrawal. Behavioral responses to heroin (e.g., stereotypy) varied widely across individuals, with rats that expressed stronger heroin preference also expressing stronger behavioral activation in response to heroin. Individual differences in preference were also related to locomotor responses to heroin but not to overt somatic withdrawal signs. CONCLUSIONS: Escalating doses of heroin evoked place preference in rats, suggesting that positive incentive-motivational value is attributed to this clinically relevant pattern of drug exposure. This study offers an improved preclinical model for studying dependence and withdrawal and provides insight into individual vulnerabilities to addiction-like behavior.

Associations of cardiovascular variables and HAART with cognition in middle-aged HIV-infected and uninfected women.

Despite the use of highly active anti-retroviral treatment (HAART), cognitive impairment remains prevalent in HIV. Indeed a recent study suggested that in certain instances, stopping HAART was associated with improved cognitive function (Robertson et al. Neurology 74(16):1260-1266 2010). HAART is occasionally associated with cardiovascular pathology and such pathology may be associated with cognitive impairment. To explore these associations, we assessed the relative contributions of cardiovascular variables such as hypertension and atherosclerosis, of HIV and HAART to cognition. The participants were members of the Women's Interagency HIV Study. In the analysis of cross-sectional data using general linear models, we assessed the relationship between each cardiovascular variable and Stroop interference time and symbol digit modalities test while adjusting for age, HIV, education, depression, and race/ethnicity. We also analyzed the association of summary measures of HAART use with cognition. In multivariate models, significance was limited to carotid lesions and carotid intima-medial thickness quintile (CIMT) with Stroop interference time (for carotid lesions, coefficient = 10.5, CI 3.5 to 17.5, p = 0.003, N = 1,130; for CIMT quintile, coefficient = 8.6, CI = 1.7 to 15.4, p = 0.025, N = 1,130). The summary measures of protease inhibitor use and other HAART measures were in most cases not associated with cognitive score in multivariate models. We conclude that in the HAART era among middle-aged women with HIV, carotid disease may be significantly associated with some measures of cognitive impairment. In this cross-sectional study, we could detect neither positive nor negative effects of HAART on cognition.