We recruited, screened and evaluated 80 participants into the NIAAA Screening protocol #14-AA-0181. We enrolled 72 participants into 7 protocols (14-AA-0144, 14-AA-0192 Phase 2, 15-AA-0031, 15-AA-0186, 17-AA-0114, 17-AA-0152 and 17-AA-0178). The circadian rhythm protocol #14-AA-0187 is on hold due to the pharmacy closure as we are prioritizing OUD studies (17-AA-0114) and research on radiotracers is on hold pending completion of the radiotracer laboratory. 1. Effects of Drugs in Human Brain Effects of Chronic Alcohol on Cortical Atrophy and Metabolism: Excessive alcohol consumption is associated with cortical atrophy and reduced brain glucose metabolism but the relation between these two measures has not been investigated. Here we tested the associations between cortical thickness (CT) and the cerebral metabolic rate of glucose (MRGlu) in participants with alcohol use disorder (AUD) and healthy controls (HC). Twenty HC and 19 AUD participants with no medical co-morbidities were tested within one week of last alcohol use PET and FDG to map MRGlu and MRI to assess CT. Though cognitive performance did not differ between AUD and HC, AUD had widespread decreases in CT and MRGlu. Relative MRGlu showed significant correlations with both CT and total lifetime alcohol (TLA). Causal mediation analysis revealed significant direct effects of TLA on both MRGlu and CT, which did not show mediation effects on each other. Findings suggests that AUD-hypometabolism is not just due to cortical thinning for their is reduced glucose utilization in the atrophied neuronal tissue, which is consistent with neurotoxicity from alcohol consumption in otherwise healthy alcoholics. The lack of impairments in cognitive performance highlights their limited sensitivity for alcohol-related neuropathology. Effects of cannabis in the segregation between cognitive and emotional processes. In addiction there is erosion of cognitive control towards drug taking that is accentuated by negative emotional states, which we hypothesize reflects a loss of segregation between cognitive and emotional processes. Using HCP data from 1204 adults aged 22-35, of whom 89 had cannabis dependence (CD) we derived two composite factors, one for cognition and one for emotion, that accounted for almost 50% of variance on a large neuropsychological test battery, using principal component (PC) analyses. The two PCs in the CD group were significantly correlated, such that negative emotionality was associated with poor cognition whereas they were uncorrelated in HC. In CD, but not in HC, fMRI brain activations to emotional stimuli (angry/fearful faces) correlated with activations to cognitive demand (working memory). Correlation analyses linked the cognitive and emotional component scores with the brain activations but whereas in CD there was a substantial overlap between cognitive and emotional brain-behavior associations, tis was not the case in HC. These findings support an impaired segregation between cognitive and emotional processes in CD that might contribute to impaired cognitive control under conditions of increased emotional demand. 2. Dopamine and Addiction Expectation effects on brain dopamine responses in cocaine abusers. The response to drugs is affected by expectation, which is modulated in part by dopamine (DA), which encodes for reward prediction. Here we compared effects of expectation on methylphenidate (MP)-induced striatal DA increases in 23 active cocaine abusers (CUD) and 23 healthy controls (HC), using 11Craclopride and PET both after placebo (PL) and after MP (0.5 mg/kg, i.v.). DA responses were measures as changes in the non-displaceable binding potential (BPND) obtained under four randomized conditions (1) expecting PL and receiving PL, (2) expecting PL and receiving MP, (3) expecting MP and receiving PL, (4) expecting MP and receiving MP. Expectation of MP increased pulse rate compared to expecting PL (F1,44=8.2, p=0.006). MP compared to PL increased rush, high, and anxiety, and these ratings were lower for CUD than HC but expectation did not affect these rating in either group. MP increased DA compared to PL in both groups (pFWE<0.0001), and this effect was blunted in CUD (pFWE<0.0001). There were no main effects of expectation on striatal DA release. There was, however, a group challenge expectation in caudate and midbrain (pFWE SVC<0.05), indicating that expectation of MP increased MP-induced DA release in HC but not in CUD whereas expectation of PL tended to increase MP-induced DA release in CUD but not HC. These findings are consistent with disrupted mesocortical DA function in addiction and provide further evidence of DAs involvement in processing expectation for uncertainty about drugs effects. 3. Methodological Studies- Development of an Adenosine A1 receptor partial agonist PET radioligand: In the brain adenosine A1 receptors (A1R) are implicated in substance use disorders and sleep and are a target of ifor medication development. PET radiotracers for A1R that are sensitive to competition with endogenous adenosine would enable the measurement of the dynamic interactions of endogenous adenosine with A1R as a function of the sleep-awake cycle in healthy and addicted individuals. Although, several human A1R PET tracers have been developed, most are xanthine-based antagonists that failed to demonstrate competitive binding against endogenous adenosine. Since a successful agonist A1R radiotracer is lacking, we explored nonnucleoside (3,5-dicyanopyridine and 5-cyanopyrimidine) templates. Guided by initial in vivo blood-brain (BBB) permeability testing, we designed and synthesized novel analogues, including 2-amino-4-(3-methoxyphenyl)-6-(2-(6-methylpyridin-2-yl)ethyl)pyridine-3,5-dicarbonitrile (22b), a partial A1R agonist of sub-nanomolar affinity. 11C22b, showed suitable rat BBB permeability and reproducibility. Regional brain uptake of 11C22b was consistent with A1R regional distribution in brain and was blocked by pretreatment with A1R but not A2AR ligands. 11C22b is the first BBB permeable partial agonist PET radiotracer for in vivo brain A1R agonist binding. Further studies are needed to determine its sensitivity to endogenous adenosine 4. Glymphatic system- Apparent Diffusion Coefficient Changes in Human Brain During Sleep. Rodent studies have shown that the glymphatic system clears waste products from brain during sleep due to expansion of interstitial fluid space facilitating entry of cerebrospinal fluid (CSF) into the brain. We studied water brain diffusivity during sleep and awake states and hypothesized an increase in water diffusivity during sleep would occur concomitantly with expansion of CSF. We used MRI to measure slow and fast components of the apparent diffusion coefficient (ADC) of water in the brain in 30 healthy participants, in whom we compared awake versus sleep conditions. Sleep compared to wakefulness was associated with increases in slow-ADC in cerebellum and with decreases in fast-ADC in thalamus, insula, and striatum, and density of sleep arousals was associated with these ADC changes. The CSF volume was increased during sleep and was associated with sleep-induced changes in ADCs in cerebellum. Although we hypothesized increases in ADC with sleep, we uncovered both increases in slow ADC (mostly in cerebellum) as well as decreases in fast ADC, which could reflect the distinct biological significance of fast- and slow-ADC. Our findings suggest a more complex sleep-related glymphatic function in humans compared to rodents; though the sleep-induced increases in CSF provide preliminary evidence consistent with glymphatic transport in the human brain.
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