Linking context with reward: a functional circuit from hippocampal CA3 to ventral tegmental area

Reward-motivated behavior is strongly influenced by the learned significance of contextual stimuli in the environment. However, the neural pathways that mediate context-reward relations are not well understood. We have identified a circuit from area CA3 of dorsal hippocampus to ventral tegmental area (VTA) that uses lateral septum (LS) as a relay. Theta frequency stimulation of CA3 excited VTA dopamine (DA) neurons and inhibited non-DA neurons. DA neuron excitation was likely mediated by disinhibition because local antagonism of γ-aminobutyric acid receptors blocked responses to CA3 stimulation. Inactivating components of the CA3-LS-VTA pathway blocked evoked responses in VTA and also reinstatement of cocaine-seeking by contextual stimuli. This transsynaptic link between hippocampus and VTA appears to be an important substrate by which environmental context regulates goal-directed behavior.

Supplementation with vitamin A early in life and subsequent risk of asthma

Animal models suggest that vitamin A deficiency affects lung development adversely and promotes airway hyperresponsiveness, and may predispose to an increased risk of asthma. We examined the long-term effects of vitamin A supplementation early in life on later asthma risk. In 2006-2008, we revisited participants from two cohorts in rural Nepal who were enrolled in randomised trials of vitamin A supplementation. The first cohort received vitamin A or placebo for <16 months during their pre-school years (1989-1991). The second cohort was born to mothers who received vitamin A, β-carotene or placebo before, during and after pregnancy (1994-1997). At follow-up, we asked about asthma symptoms and performed spirometry. Out of 6,421 subjects eligible to participate, 5,430 (85%) responded to our respiratory survey. Wheezing prevalence during the previous year was 4.8% in participants aged 9-13 yrs and 6.6% in participants aged 14-23 yrs. We found no differences between the vitamin A supplemented and placebo groups from either trial in the prevalence of lifetime or current asthma and wheeze or in spirometric indices of obstruction (p ≥ 0.12 for all comparisons). Vitamin A supplementation early in life was not associated with a decreased risk of asthma in an area with chronic vitamin A deficiency.

Differentiating the rapid actions of cocaine

The subjective effects of intravenous cocaine are felt almost immediately, and this immediacy plays an important part in the drug's rewarding impact. The primary rewarding effect of cocaine involves blockade of dopamine reuptake; however, the onset of this action is too late to account for the drug's initial effects. Recent studies suggest that cocaine-predictive cues--including peripheral interoceptive cues generated by cocaine itself--come to cause more direct and earlier reward signalling by activating excitatory inputs to the dopamine system. The conditioned activation of the dopamine system by cocaine-predictive cues offers a new target for potential addiction therapies.

Dorsal as well as ventral striatal lesions affect levels of intravenous cocaine and morphine self-administration in rats

While the ventral striatum has long been implicated in the rewarding properties of psychomotor stimulants and opiates, little attention has been paid to the possible contribution of more dorsal regions of the striatum. We have thus examined the effects of lesions in three different striatal subregions on cocaine and morphine self-administration. Different groups of rats were trained to self-administer intravenous cocaine (1.0mg/kg/infusion) or morphine (0.5mg/kg/infusion) first under fixed ratio (FR) and then under progressive ratio (PR) schedules of reinforcement. Upon completion of the training, independent groups received bilateral electrolytic or sham lesions of the dorsal portion of the caudate-putamen (dCPu), the ventral portion of the caudate-putamen (vCPu) or the more ventral nucleus accumbens (NAS). Following recovery, they were tested for self-administration of cocaine (0.25, 0.5, 1.0 and 1.5mg/kg/infusion) or morphine (0.125, 0.25, 0.5 and 0.75mg/kg/infusion) under the PR schedule. The PR responding for each drug was significantly reduced in a dose-dependent manner following lesions of dCPu, vCPu and NAS. While the relative effectiveness of these lesions is likely to be specific to the conditions of this experiment, NAS lesions reduced self-administration of each drug to a greater extent than did dCPu or vCPu lesions.

The minimal important difference of exercise tests in severe COPD

Our aim was to determine the minimal important difference (MID) for 6-min walk distance (6MWD) and maximal cycle exercise capacity (MCEC) in patients with severe chronic obstructive pulmonary disease (COPD). 1,218 patients enrolled in the National Emphysema Treatment Trial completed exercise tests before and after 4-6 weeks of pre-trial rehabilitation, and 6 months after randomisation to surgery or medical care. The St George's Respiratory Questionnaire (domain and total scores) and University of California San Diego Shortness of Breath Questionnaire (total score) served as anchors for anchor-based MID estimates. In order to calculate distribution-based estimates, we used the standard error of measurement, Cohen's effect size and the empirical rule effect size. Anchor-based estimates for the 6MWD were 18.9 m (95% CI 18.1-20.1 m), 24.2 m (95% CI 23.4-25.4 m), 24.6 m (95% CI 23.4-25.7 m) and 26.4 m (95% CI 25.4-27.4 m), which were similar to distribution-based MID estimates of 25.7, 26.8 and 30.6 m. For MCEC, anchor-based estimates for the MID were 2.2 W (95% CI 2.0-2.4 W), 3.2 W (95% CI 3.0-3.4 W), 3.2 W (95% CI 3.0-3.4 W) and 3.3 W (95% CI 3.0-3.5 W), while distribution-based estimates were 5.3 and 5.5 W. We suggest a MID of 26 ± 2 m for 6MWD and 4 ± 1 W for MCEC for patients with severe COPD.

Extracellular fluctuations of dopamine and glutamate in the nucleus accumbens core and shell associated with lever-pressing during cocaine self-administration, extinction, and yoked cocaine administration

RATIONALE

Dopamine and glutamate in the nucleus accumbens (NAS) are differentially implicated in cocaine-directed behavior.

OBJECTIVES

We sought to compare extracellular fluctuations of dopamine and glutamate in core and shell of NAS associated with operant responding during cocaine self-administration, extinction, and yoked cocaine administration.

METHODS

Rats were trained to lever-press for cocaine or saline under FR1 before undergoing microdialysis testing during cocaine self-administration, extinction, or yoked cocaine administration. Microdialysis samples were collected every 20 min and were analyzed for dopamine and glutamate with high-performance liquid chromatography.

RESULTS

Rats actively lever-pressed during cocaine self-administration and extinction. However, lever-pressing was minimal during yoked cocaine administration in both cocaine-trained and saline-trained rats. Dopamine was elevated throughout cocaine self-administration and yoked cocaine administration. The extent of cocaine-evoked dopamine was greater in shell than in core, greater in cocaine-trained than in saline-trained rats, and greater during self-administration than during yoked administration. Dopamine was also elevated in core (first 60 min) and in shell (first 40 min) during extinction. Basal concentration of glutamate, but not dopamine, was lower in cocaine-trained than in saline-trained rats. In cocaine-trained rats, glutamate was elevated during cocaine self-administration and extinction but was depressed below baseline during yoked cocaine administration. The extent and direction of glutamate fluctuation was similar between core and shell. In saline-trained rats, glutamate was not affected by yoked cocaine.

CONCLUSION

Distinct patterns of dopamine and glutamate fluctuations in core and shell appear to underlie characteristic patterns of lever-pressing associated with cocaine self-administration, extinction, and yoked cocaine administration.

Methamphetamine acts on subpopulations of neurons regulating sexual behavior in male rats

Methamphetamine (Meth) is a highly addictive stimulant. Meth abuse is commonly associated with the practice of sexual risk behavior and increased prevalence of Human Immunodeficiency Virus and Meth users report heightened sexual desire, arousal, and sexual pleasure. The biological basis for this drug-sex nexus is unknown. The current study demonstrates that Meth administration in male rats activates neurons in brain regions of the mesolimbic system that are involved in the regulation of sexual behavior. Specifically, Meth and mating co-activate cells in the nucleus accumbens core and shell, basolateral amygdala, and anterior cingulate cortex. These findings illustrate that in contrast to current belief drugs of abuse can activate the same cells as a natural reinforcer, that is sexual behavior, and in turn may influence compulsive seeking of this natural reward.

Roles for nigrostriatal--not just mesocorticolimbic--dopamine in reward and addiction

Forebrain dopamine circuitry has traditionally been studied by two largely independent specialist groups: students of Parkinson's disease who study the nigrostriatal dopamine system that originates in the substantia nigra (SN), and students of motivation and addiction who study the role of the mesolimbic and mesocortical dopamine systems that originate in the ventral tegmental area (VTA). The anatomical evidence for independent nigrostriatal and mesolimbic dopamine systems has, however, long been obsolete. There is now compelling evidence that both nominal "systems" participate in reward function and addiction. Electrical stimulation of both SN and VTA is rewarding, blockade of glutamatergic or cholinergic input to either SN or VTA attenuates the habit-forming effects of intravenous cocaine, and dopamine in both nigrostriatal and mesocorticolimbic terminal fields participates in the defining property of rewarding events: the reinforcement of memory consolidation. Thus, the similarities between nigrostriatal and mesolimbic dopamine systems can be as important as their differences.

Control of within-binge cocaine-seeking by dopamine and glutamate in the core of nucleus accumbens

RATIONALE

Dopamine and glutamate are thought to interact in the ventral striatum and to play important roles there in the cocaine-seeking of cocaine-experienced animals.

OBJECTIVES

We sought to determine the relative roles of the two transmitters in the two major zones of the nucleus accumbens (NAS), the core and shell subregions.

METHODS

We assessed the effects of dopamine and glutamate receptor blockade in the core and shell on intravenous cocaine self-administration in rats. Trained animals were allowed to self-administer cocaine for an initial hour, and then D1-type or D2-type dopamine receptor blockers or NMDA-type or AMPA-type glutamate receptor blockers were infused by reverse microdialysis into one of the two regions for an additional 3 h of testing.

RESULTS

The D1-type antagonist SCH23390 and the D2-type antagonist raclopride each increased cocaine intake whereas the AMPA-type antagonist CNQX decreased responding when infused into the core. SCH23390 increased cocaine intake less strongly when infused into the shell, while raclopride and CNQX were each ineffective when infused into the shell. The NMDA-antagonist CPP failed to affect cocaine self-administration when infused into either site.

CONCLUSIONS

These findings implicate the core of NAS in the maintenance of established cocaine self-administration in trained animals, despite the fact that the reinforcement of responding in untrained animals appears to results from cocaine actions in the olfactory tubercle and medial shell and not the core of accumbens.

Associations of IL6 polymorphisms with lung function decline and COPD

BACKGROUND

Interleukin-6 (IL6) is a pleiotropic pro-inflammatory and immunomodulatory cytokine which probably plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). There is a functional single nucleotide polymorphism (SNP), -174G/C, in the promoter region of IL6. It was hypothesised that IL6 SNPs influence susceptibility for impaired lung function and COPD in smokers.

METHODS

Seven and five SNPs in IL6 were genotyped in two nested case-control samples derived from the Lung Health Study (LHS) based on phenotypes of rate of decline of forced expiratory volume in 1 s (FEV(1)) over 5 years and baseline FEV(1) at the beginning of the LHS. Serum IL6 concentrations were measured for all subjects. A partially overlapping panel of nine IL6 SNPs was genotyped in 389 cases of COPD from the National Emphysema Treatment Trial (NETT) and 420 controls from the Normative Aging Study (NAS).

RESULTS

In the LHS, three IL6 SNPs were associated with decline in FEV(1) (0.023< or =p< or =0.041 in additive models). Among them, the IL6_-174C allele was associated with a rapid decline in lung function. The association was more significant in a genotype-based analysis (p = 0.006). In the NETT-NAS study, IL6_-174G/C and four other IL6 SNPs, all of which are in linkage disequilibrium with IL6_-174G/C, were associated with susceptibility to COPD (0.01< or =p< or =0.04 in additive genetic models).

CONCLUSION

The results suggest that the IL6_-174G/C SNP is associated with a rapid decline in FEV(1) and susceptibility to COPD in smokers.

Leptin receptor polymorphisms and lung function decline in COPD

Only a fraction of all smokers develop chronic obstructive pulmonary disease (COPD), suggesting a large role for genetic susceptibility. The leptin receptor (LEPR) is present in human lung tissue and may play a role in COPD pathogenesis. The present study examined the association between genetic variants in the LEPR gene and lung function decline in COPD. In total, 429 European Americans were randomly selected from the National Heart Lung and Blood Institute Lung Health Study. 36 single nucleotide polymorphisms (SNPs) in LEPR were genotyped using the Illumina GoldenGate platform (Broad Institute, Cambridge, MA, USA). Mean annual decline in forced expiratory volume in 1 s % predicted over the 5-yr period was calculated using linear regression. Linear regression models were also used to adjust for potential confounders. In addition, in vivo expression of the receptor gene was assessed with immunohistochemistry on lungs from smoke-exposed inbred mice. We identified significant associations (p<0.05) between lung function decline and 21 SNPs. Haplotype analyses confirmed several of these associations seen with individual markers. Immunohistochemistry results in inbred mice strains support a potential role of LEPR in COPD pathogenesis. We identified genetic variants in the LEPR gene significantly associated with lung function decline in a population of smokers with COPD. Our results support a role for LEPR as a novel candidate gene for COPD.

Dopamine and reward: the anhedonia hypothesis 30 years on

The anhedonia hypothesis--that brain dopamine plays a critical role in the subjective pleasure associated with positive rewards--was intended to draw the attention of psychiatrists to the growing evidence that dopamine plays a critical role in the objective reinforcement and incentive motivation associated with food and water, brain stimulation reward, and psychomotor stimulant and opiate reward. The hypothesis called to attention the apparent paradox that neuroleptics, drugs used to treat a condition involving anhedonia (schizophrenia), attenuated in laboratory animals the positive reinforcement that we normally associate with pleasure. The hypothesis held only brief interest for psychiatrists, who pointed out that the animal studies reflected acute actions of neuroleptics whereas the treatment of schizophrenia appears to result from neuroadaptations to chronic neuroleptic administration, and that it is the positive symptoms of schizophrenia that neuroleptics alleviate, rather than the negative symptoms that include anhedonia. Perhaps for these reasons, the hypothesis has had minimal impact in the psychiatric literature. Despite its limited heuristic value for the understanding of schizophrenia, however, the anhedonia hypothesis has had major impact on biological theories of reinforcement, motivation, and addiction. Brain dopamine plays a very important role in reinforcement of response habits, conditioned preferences, and synaptic plasticity in cellular models of learning and memory. The notion that dopamine plays a dominant role in reinforcement is fundamental to the psychomotor stimulant theory of addiction, to most neuroadaptation theories of addiction, and to current theories of conditioned reinforcement and reward prediction. Properly understood, it is also fundamental to recent theories of incentive motivation.

Cocaine serves as a peripheral interoceptive conditioned stimulus for central glutamate and dopamine release

Intravenous injections of cocaine HCl are habit-forming because, among their many actions, they elevate extracellular dopamine levels in the terminal fields of the mesocorticolimbic dopamine system. This action, thought to be very important for cocaine's strong addiction liability, is believed to have very short latency and is assumed to reflect rapid brain entry and pharmacokinetics of the drug. However, while intravenous cocaine HCl has almost immediate effects on behavior and extracellular dopamine levels, recent evidence suggests that its central pharmacological effects are not evident until 10 or more seconds after IV injection. Thus the immediate effects of a given intravenous cocaine injection on extracellular dopamine concentration and behavior appear to occur before there is sufficient time for cocaine to act centrally as a dopamine uptake inhibitor. To explore the contribution of peripheral effects of cocaine to the early activation of the dopamine system, we used brain microdialysis to measure the effects of cocaine methiodide (MI)--a cocaine analogue that does not cross the blood brain barrier--on glutamate (excitatory) input to the dopamine cells. IP injections of cocaine MI were ineffective in cocaine-naïve animals but stimulated ventral tegmental glutamate release in rats previously trained to lever-press for cocaine HCl. This peripherally triggered glutamate input was sufficient to reinstate cocaine-seeking in previously trained animals that had undergone extinction of the habit. These findings offer an explanation for short-latency behavioral responses and immediate dopamine elevations seen following cocaine injections in cocaine-experienced but not cocaine-naïve animals.

Ventral tegmental glutamate: a role in stress-, cue-, and cocaine-induced reinstatement of cocaine-seeking

Ventral tegmental dopamine neurons are activated by primary rewards and, when such rewards are predictable' by reward-predicting stimuli. Glutamatergic input to the ventral tegmental area contributes to this activation: in animals trained to self-administer cocaine, cocaine-predictive cues trigger ventral tegmental glutamate release and dopaminergic activation. Mild footshock stress similarly causes glutamate release and dopaminergic activation in cocaine-trained but not cocaine-naïve animals. The ability of cocaine-predictive and stress-associated cues to activate the dopamine system and to trigger cocaine craving appears to be related to changes in the ability of glutamate to activate dopaminergic neurons, changes known to be caused by experience with stress or with drugs of abuse.

Functional implications of glutamatergic projections to the ventral tegmental area

Glutamatergic afferents of the ventral tegmental area (VTA) play an important role in the functioning of the VTA and are involved in the pathophysiology of drug addiction. It has recently been demonstrated that the VTA is densely innervated by glutamatergic axons and that glutamatergic neurons projecting to the VTA are situated in almost all structures that project there. While the projection from the prefrontal cortex is essentially entirely glutamatergic, subcortical glutamatergic neurons innervating the VTA intermingle with non-glutamatergic, most likely GABAergic and/or peptidergic VTA-projecting neurons. The first part of this review focuses on the origins and putative functional implications of various glutamatergic projections to the VTA. In the second part we consider how different neuropeptides via different mechanisms modulate glutamatergic actions in the VTA. We conclude by developing a model of how the glutamatergic afferents might together contribute to the functions of the VTA.

A role for conditioned ventral tegmental glutamate release in cocaine seeking

Initiation of cocaine self-administration in rats was associated with release of glutamate in the ventral tegmental area (VTA). The glutamate release was transient, despite continued cocaine intake. Similar glutamate release was seen in rats earning, for the first time, unexpected saline rather than expected cocaine. VTA glutamate release was not seen in similarly trained rats earning saline instead of cocaine for the 13th time. VTA glutamate release was also seen in similarly trained rats that received yoked rather than earned cocaine injections on test day. VTA glutamate release was not seen in a group of rats that had never earned cocaine but had received yoked injections during the training period. Glutamate release was also not seen in a group of rats that received yoked injections but had no previous experience with cocaine. VTA GABA levels did not fluctuate during any aspect of cocaine seeking. Blockade of VTA glutamate receptors appeared to attenuate the rewarding effects of intravenous cocaine injections and blocked almost completely the conditioned responding normally seen during extinction trials. These findings indicate that VTA glutamate release is a conditioned response dependent on an associative process and is not a simple consequence of previous cocaine exposure. The findings implicate glutamate as at least one of the sources of VTA signals from reward-associated environmental stimuli.

Stress-induced relapse to cocaine seeking: roles for the CRF(2) receptor and CRF-binding protein in the ventral tegmental area of the rat

RATIONALE

Footshock reinstates cocaine seeking in cocaine-experienced rats by inducing corticotropin-releasing factor (CRF) and glutamate release in the ventral tegmental area (VTA) and thus activating VTA dopaminergic neurons. Footshock-induced VTA glutamate release, dopamine activation and reinstatements are blocked by VTA administration of a alpha-helical CRF, a nonselective CRF receptor antagonist. The effects of selective CRF antagonists have not yet been reported.

OBJECTIVE

The present studies were designed to explore the roles of VTA CRF receptor subtypes and CRF-BP in these effects induced by footshock.

METHODS

Rats were first trained to lever-press for intravenous cocaine (1 mg/infusion/0.13 ml, FR-1 schedule), and then tested under extinction conditions until response rates returned to the pretraining baseline. Reinstatements, VTA glutamate and dopamine levels [microdialysis with high performance liquid chromatography (HPLC)] were then assessed, under various pharmacological conditions, after mild inescapable footshock.

RESULTS

Footshock-induced reinstatement of cocaine seeking and release of VTA glutamate and dopamine were blocked by selective blockade of VTA CRF(2) receptors (CRF(2)Rs) but not CRF(1)Rs. VTA perfusion of CRF or CRF(2)R agonists that have strong affinity for CRF-BP mimicked the effects induced by footshock while CRFR agonists that do not bind CRF-BP were ineffective. CRF(6-33), which competes for the CRF binding site on CRF-BP, attenuated the effects of CRF or urocortin I on VTA glutamate and dopamine release and on reinstatement of cocaine seeking.

CONCLUSIONS

The present studies revealed a role of VTA CRF-BP and suggest an involvement of CRF(2)R in the effectiveness of stress in triggering glutamate and dopamine release and cocaine seeking in drug-experienced animals.

Long-term upregulation of protein kinase A and adenylate cyclase levels in human smokers

Repeated injections of cocaine and morphine in laboratory rats cause a variety of molecular neuroadaptations in the cAMP signaling pathway in nucleus accumbens and ventral tegmental area. Here we report similar neuroadaptations in postmortem tissue from the brains of human smokers and former smokers. Activity levels of two major components of cAMP signaling, cAMP-dependent protein kinase A (PKA) and adenylate cyclase, were abnormally elevated in nucleus accumbens of smokers and in ventral midbrain dopaminergic region of both smokers and former smokers. Protein levels of the catalytic subunit of PKA were correspondingly higher in the ventral midbrain dopaminergic region of both smokers and former smokers. Protein levels of other candidate neuroadaptations, including glutamate receptor subunits, tyrosine hydroxylase, and other protein kinases, were within normal range. These findings extend our understanding of addiction-related neuroadaptations of cAMP signaling to tobacco smoking in human subjects and suggest that smoking-induced brain neuroadaptations can persist for significant periods in former smokers.

Heteromeric nicotinic acetylcholine-dopamine autoreceptor complexes modulate striatal dopamine release

In the striatum, dopamine and acetylcholine (ACh) modulate dopamine release by acting, respectively, on dopamine D(2) autoreceptors and nicotinic ACh (nACh) heteroreceptors localized on dopaminergic nerve terminals. The possibility that functional interactions exist between striatal D(2) autoreceptors and nACh receptors was studied with in vivo microdialysis in freely moving rats. Local perfusion of nicotine in the ventral striatum (shell of the nucleus accumbens) produced a marked increase in the extracellular levels of dopamine, which was completely counteracted by co-perfusion with either the non-alpha(7) nACh receptor antagonist dihydro-beta-erythroidine or the D(2-3) receptor agonist quinpirole. Local perfusion of the D(2-3) receptor antagonist raclopride produced an increase in the extracellular levels of dopamine, which was partially, but significantly, counteracted by coperfusion with dihydro-beta-erythroidine. These findings demonstrate a potent crosstalk between G protein-coupled receptors and ligand-gated ion channels in dopaminergic nerve terminals, with the D(2) autoreceptor modulating the efficacy of non-alpha(7) nACh receptor-mediated modulation of dopamine release. We further demonstrate physical interactions between beta(2) subunits of non-alpha(7) nicotinic acetylcholine receptors and D(2) autoreceptors in co-immunoprecipitation experiments with membrane preparations from co-transfected mammalian cells and rat striatum. These results reveal that striatal non-alpha(7) nicotinic acetylcholine receptors form part of heteromeric dopamine autoreceptor complexes that modulate dopamine release.

Role of brain dopamine in food reward and reinforcement

The ability of food to establish and maintain response habits and conditioned preferences depends largely on the function of brain dopamine systems. While dopaminergic transmission in the nucleus accumbens appears sufficient for some forms of reward, the role of dopamine in food reward does not appear to be restricted to this region. Dopamine plays an important role in both the ability to energize feeding and to reinforce food-seeking behaviour; the role in energizing feeding is secondary to the prerequisite role in reinforcement. Dopaminergic activation is triggered by the auditory and visual as well as the tactile, olfactory, and gustatory stimuli of foods. While dopamine plays a central role in the feeding and food-seeking of normal animals, some food rewarded learning can be seen in genetically engineered dopamine-deficient mice.

Two brain sites for cannabinoid reward

The recent findings that Delta9tetrahydrocannabinol (Delta9THC), the active agent in marijuana and hashish, (1) is self-administered intravenously, (2) potentiates the rewarding effects of electrical brain stimulation, and (3) can establish conditioned place preferences in laboratory animals, suggest that these drugs activate biologically primitive brain reward mechanisms. Here, we identify two chemical trigger zones for stimulant and rewarding actions of Delta9THC. Microinjections of Delta9THC into the posterior ventral tegmental area (VTA) or into the shell of the nucleus accumbens (NAS) increased locomotion, and rats learned to lever-press for injections of Delta9THC into each of these regions. Substitution of vehicle for drug or treatment with a cannabinoid CB1 receptor antagonist caused response cessation. Microinjections of Delta9THC into the posterior VTA and into the posterior shell of NAS established conditioned place preferences. Injections into the core of the NAS, the anterior VTA, or dorsal to the VTA were ineffective. These findings link the sites of rewarding action of Delta9THC to brain regions where such drugs as amphetamines, cocaine, heroin, and nicotine are also thought to have their sites of rewarding action.

C-reactive protein and mortality in mild to moderate chronic obstructive pulmonary disease

BACKGROUND

Although C-reactive protein (CRP) levels are increased in chronic obstructive pulmonary disease (COPD), it is not certain whether they are associated with adverse clinical outcomes.

METHODS

Serum CRP levels were measured in 4803 participants in the Lung Health Study with mild to moderate COPD. The risk of all-cause and disease specific causes of mortality was determined as well as cardiovascular event rates, adjusting for important covariates such as age, sex, cigarette smoking, and lung function. Cardiovascular events were defined as death from coronary heart disease or stroke, or non-fatal myocardial infarction or stroke requiring admission to hospital.

RESULTS

CRP levels were associated with all-cause, cardiovascular, and cancer specific causes of mortality. Individuals in the highest quintile of CRP had a relative risk (RR) for all-cause mortality of 1.79 (95% confidence interval (CI) 1.25 to 2.56) compared with those in the lowest quintile of CRP. For cardiovascular events and cancer deaths the corresponding RRs were 1.51 (95% CI 1.20 to 1.90) and 1.85 (95% CI 1.10 to 3.13), respectively. CRP levels were also associated with an accelerated decline in forced expiratory volume in 1 second (p < 0.001). The discriminative property of CRP was greatest during the first year of measurement and decayed over time. Comparing the highest and lowest CRP quintiles, the RR was 4.03 (95% CI 1.23 to 13.21) for 1 year mortality, 3.30 (95% CI 1.38 to 7.86) for 2 year mortality, and 1.82 (95% CI 1.22 to 2.68) for > or =5 year mortality.

CONCLUSIONS

CRP measurements provide incremental prognostic information beyond that achieved by traditional markers of prognosis in patients with mild to moderate COPD, and may enable more accurate detection of patients at a high risk of mortality.