Recovery of brain glucose metabolism in detoxified alcoholics

PET imaging studies in drug abuse

In spite of the massive public health problem associated with drug abuse, effective treatments remain elusive. This is due in part to a relatively poor understanding of the neurochemical changes which drugs of abuse produce in the human brain and the relationship of these changes to the behavioral and addictive properties of drugs. With the development of modern imaging methods and a variety of labeled drugs and radiotracers, it has now become possible to track many aspects of drug pharmacokinetics and pharmacodynamics directly in the human brain and to relate these parameters to the behavioral and toxic properties of drugs.

REVIEW

In this article, we will highlight some examples of the use of Positron Emission Tomography to measure drug pharmacokinetics and pharmacodynamics and their relationship to addiction and to toxicity.

Brain imaging in alcoholism

Copyright Rapid Science Ltd

Brain abnormalities in murderers indicated by positron emission tomography

Murderers pleading not guilty by reason of insanity (NGRI) are thought to have brain dysfunction, but there have been no previous studies reporting direct measures of both cortical and subcortical brain functioning in this specific group. Positron emission tomography brain imaging using a continuous performance challenge task was conducted on 41 murderers pleading not guilty by reason of insanity and 41 age- and sex-matched controls. Murderers were characterized by reduced glucose metabolism in the prefrontal cortex, superior parietal gyrus, left angular gyrus, and the corpus callosum, while abnormal asymmetries of activity (left hemisphere lower than right) were also found in the amygdala, thalamus, and medial temporal lobe. These preliminary findings provide initial indications of a network of abnormal cortical and subcortical brain processes that may predispose to violence in murderers pleading NGRI.

Brain glucose metabolism in borderline personality disorder

We searched for regional cerebral metabolic disturbances in patients with borderline personality disorder (BPD). Ten inpatients with BPD, no current DSM-IIIR Axis I diagnosis and free of any psychotropic substances, were compared with 15 age-matched control subjects using positron emission tomography with 2-deoxy-2-[18F]fluoro-D-glucose and semiquantitative analysis of regional glucose metabolic activity. We found relative hypometabolism in patients with borderline personality disorder at the level of the premotor and prefrontal cortical areas, the anterior part of the cingulate cortex and the thalamic, caudate and lenticular nuclei. This study shows significant cerebral metabolic disturbances in patients with borderline personality disorder. These metabolic disturbances, which are similar to some of those described in other psychiatric entities, may help to understand the characteristic clinical aspects of this disorder.

Effects of abstinence and relapse upon neuropsychological function and cerebral glucose metabolism in severe chronic alcoholism

Prolonged excessive consumption of alcohol has been associated with a variety of cognitive disorders accompanied by neuropathological and neurochemical abnormalities of the brain, particularly in the frontal lobes. Studies with positron emission tomography (PET) have shown decreased local cerebral metabolic rates for glucose (lCMRglc) in frontal regions, with correlated abnormalities on neuropsychological tests sensitive to executive functioning. This investigation was designed as a pilot study to examine the effects of abstinence and relapse in patients with severe chronic alcoholism studied longitudinally with PET and with neuropsychological evaluation to assess both general and executive functioning. Six patients, including 4 who remained relatively abstinent and 2 who relapsed following their initial evaluation, were studied twice, with inter-evaluation intervals ranging from 10 to 32 months. The patients who remained abstinent or who had minimal alcohol use showed partial recovery of lCMRglc in two of three divisions of the frontal lobes and improvement on neuropsychological tests of general cognitive and executive functioning, whereas the patients who relapsed had further declines in these areas. These results, although based upon a relatively small number of subjects, provide preliminary support for at least partial recovery of metabolic and cognitive functioning in individual patients who abstain from alcohol.

Functional EEG mapping and SPECT in detoxified male alcoholics

Fifteen alcoholics diagnosed according to DSM-III-R, who were detoxified for at least 2 weeks and showed no clinical withdrawal signs, were investigated with 16 channel EEG mapping during resting, manumotor and music perception conditions, and were compared with 13 control persons. Single photon emission computed tomography (SPECT) using hexa-methyl-propilene-amine-oxime (HMPAO) labeled with 99m-technetium (99mTc) as tracer was performed separately (in patients only) and submitted to semiquantitative region of interest (ROI) analysis in 2 slices, 6 and 10 cm above canthomeatal line, respectively. Resting EEG showed increased power values in fast beta frequency band for the detoxified alcoholics. On cortical stimulation, patients showed signs of pathological EEG reactivity. Correlations of EEG parameters to cerebral blood flow (CBF) values (patients only) yielded coefficients around zero for all frequency bands (signs of uncoupling). All findings point to organic brain dysfunctions in these patients which extend beyond the period of withdrawal.

Decreases in dopamine receptors but not in dopamine transporters in alcoholics

It has been hypothesized that ethanol's actions on the dopamine (DA) system may participate in addiction. The purpose of this study was to evaluate the DA system in the brain of alcoholics. We evaluated 10 alcoholics and 17 nonalcoholics using positron emission tomography and [11C]raclopride to measure DA D2 receptors. In addition, in 5 of the alcoholics and 16 of the nonalcoholics, we also measured DA transporters with [11C]d-threo methylphenidate. The ratio of the distribution volumes in striatum to that in cerebellum, which corresponds to Bmax/Kd + 1, was used as model parameter of DA D2 receptor and transporter availability. Dopamine D2 receptor availability (Bmax/Kd) was significantly lower in alcoholics (2.1 +/- 0.5) than in nonalcoholics (2.7 +/- 0.6) (p < 0.05) and was not correlated with days since last alcohol use. Alcoholics showed DA transporter values similar to those in nonalcoholics. The ratio of DA D2 receptor to transporter availability was significantly higher in nonalcoholics (1.4 +/- 0.1) than in alcoholics (1.1 +/- 0.1) (p < 0.005). Alcoholics showed significant reductions in D2 receptors (postsynaptic marker) but not in DA transporter availability (presynaptic marker) when compared with nonalcoholics. Because D2 receptors in striatum are mainly localized in gamma-aminobutyric acid (GABA) cells these results provide evidence of GABAergic involvement in the dopaminergic abnormalities seen in alcoholics.

Effects of disulfiram on positron emission tomography and neuropsychological studies in severe chronic alcoholism

Disulfiram is an aldehyde dehydrogenase inhibitor that is widely used as an adjunctive agent in the treatment of patients with severe chronic alcoholism. Recent positron emission tomography (PET) studies of local cerebral metabolic rates for glucose (ICMRglc) and benzodiazepine receptor binding in alcoholic patients have shown regional cerebral abnormalities; however, some of the patients were studied while receiving disulfiram, which could influence the biochemical processes under investigation. In a retrospective investigation, we examined the influence of disulfiram administration on the results of PET studies of ICMRglc and benzodiazepine receptor binding and neuropsychological tests of cognition and executive function in patients with severe chronic alcoholism. [18F]Fluorodeoxyglucose was used to measure ICMRglc in 48 male patients, including 11 receiving and 37 not receiving disulfiram in therapeutic doses. [11C]Flumazenil was used to measure benzodiazepine receptor binding in 17 male patients, including 3 receiving and 14 not receiving disulfiram. All patients studied with FMZ were also examined with fluorodeoxyglucose. PET studies of ICMRglc revealed significantly decreased global values in the patients receiving disulfiram compared with those not receiving disulfiram. PET studies of benzodiazepine receptor binding revealed decreased flumazenil influx and distribution volume in patients receiving disulfiram. The neuropsychological tests demonstrated no differences between the two groups of subjects. The findings suggest that disulfiram may influence the results of PET studies of glucose metabolism and benzodiazepine receptor binding.

Single photon emission computed tomography with iodoamphetamine-123 and neuropsychological studies in long-term abstinent alcoholics

Ten long-term abstinent alcoholics (mean abstinence = 7.7 years) were compared with 13 recently detoxified substance-dependent inpatients (mean abstinence = 25 days) and 8 nonalcoholic control subjects on global end regional measures of cortical cerebral blood flow (CBF), and on neuropsychological measures. CBF was assessed using 123iodoamphetamine (IMP) single photon emission computed tomography (SPECT) under conditions of behavioral challenge (Raven's Progressive Matrices). CBF and neuropsychological test performance were worse in the recently detoxified inpatients. Of greater interest, there was a dissociation in the long-term abstinent group, which, while neuropsychologically indistinguishable from controls, showed significantly decreased mean cortical IMP uptake. We conclude that there may be persistent physiologic abnormalities in long-term abstinent alcoholics who have achieved full behavioral recovery. Smoking on the day of SPECT scanning was also identified to be a significant confound to understanding CBF changes in alcoholism.

Postbinge effects of acute alcohol intoxication on hepatic free radical formation

The present studies were performed to test the hypothesis that Kupffer and endothelial cells are activated after recovery from an acute alcohol binge, which is accompanied by formation of oxygen-derived radicals. These radicals have been implicated in the pathogenesis of alcohol-mediated tissue injury in a number of organs. Male Sprague-Dawley rats received an intravenous injection of 20% ethanol in saline (1.75 g/kg), followed by an intravenous infusion (250 to 300 mg/kg/hr) for 12 hr. At the end of 12-hr infusion, ethanol was replaced by saline, and the infusion was continued for a further 6 hr. This was referred to as the recovery period. The 6-hr recovery period was selected because superoxide anion generation by the perfused liver peaked at this time point. Superoxide anion formation by the perfused liver was measured by the superoxide dismutase-inhibitable reduction of ferricytochrome c. Kupffer and endothelial cells were isolated for the determination of in vivo glucose uptake and in vitro superoxide anion release. Results show that a significant (p < 0.05) amount of superoxide (1.54 nmol/min/g) was generated by the perfused liver at 6 hr recovery after 12 hr of ethanol infusion. Serum ALT activity was also elevated in this treatment group. Time-matched control-saline infused animals or ethanol-treated animals without a recovery period released < 0.2 nmol/min/g of superoxide. The postrecovery superoxide production and an accompanying increase in the in vivo glucose uptake were also observed in isolated Kupffer and endothelial cells. Depletion of Kupffer cells by gadolinium chloride before ethanol treatment and recovery was associated with significant attenuation of free radical formation by the perfused liver and reduction of serum ALT. These studies demonstrate that recovery from an acute alcohol binge has a stimulating effect on hepatic sinusoidal superoxide production, and it may also affect liver function.

Longitudinal changes in magnetic resonance imaging brain volumes in abstinent and relapsed alcoholics

Chronic alcoholism is associated with smaller volumes of cortical gray matter and white matter and a complementary increase in brain cerebrospinal fluid (CSF) volumes, relative to age norms. This longitudinal study quantified the extent of brain volume changes associated with abstinence and drinking at three time points in chronic alcoholics. We obtained magnetic resonance imaging (MRI) on 58 alcoholic men after an average of 12 days (MRI-1) and 32 days (MRI-2) of sobriety. In addition, 58 healthy control subjects were scanned at a comparable interval. At MRI-3, 11 controls and 39 alcoholics were rescanned, 2-12 months after MRI-2; 19 alcoholics had abstained, and 20 had resumed drinking. Axial MRI slices were segmented into cortical gray matter, white matter, and CSF and summed over seven slices; lateral and third ventricular volumes were also estimated. MRI volume changes were corrected using an estimate of interscan measurement error caused by head positioning differences, and then divided by the interval to yield rates of change (slopes). From MRI-1 to MRI-2, the alcoholic group showed declines in CSF volumes of the lateral ventricles and posterior cortical sulci, and a trend toward an increase in anterior cortical gray matter volume relative to the control group. From MRI-2 to MRI-3, third ventricular volumes decreased in the abstainers relative to the relapsers and controls; cortical white matter volume decreased in the relapsers. In the relapsers, lifetime consumption of alcohol (as of MRI-1) predicted later vulnerability to white matter volume decline and third ventricular enlargement with resumption of drinking. These data suggest that improvement in cortical gray matter, sulcal, and lateral ventricular volumes occur early in the course of abstinence, and that improvement in third ventricular volume appears later with continued abstinence.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed P3A in abstinent elderly male chronic alcoholics

Significant central nervous system toxicity in frontal brain regions has been demonstrated with chronic alcohol consumption both on autopsy and using neuropsychological testing. This study examined the latency of an objective and reproducible brain event-related potential measure of frontal cortex function in chronic elderly male alcoholics who were abstinent 3 months-2 years, a patient group in whom the central nervous system effects of chronic alcohol abuse are thought to be largest and most persistent. We examined the latency of the P3A event-related potential component, which reflects a frontal maximum orienting response to novel stimuli. Twelve elderly abstinent chronic alcoholic males and 11 elderly male controls were studied in an auditory and a visual paradigm, each of which included target, nontarget, and novel rare nontarget conditions. In both modalities, the P3A response to the novel rare nontarget stimuli was significantly delayed in the chronic alcoholics. P3B delays to the target stimuli were also present in the alcoholics, with the P3A and P3B effects being independent of each other. For both P3A and P3B, the effects were larger and more consistent in the visual compared with the auditory modality. Our conclusions are as follows: (1) both P3A and P3B latency delays are evident in elderly abstinent chronic alcoholics; (2) separate mechanisms are responsible for these effects; (3) these effects are more sensitively detected in the visual versus the auditory modality; and (4) delayed P3A latency may be an objective and reproducible index of the frontal cortex effects of chronic alcohol abuse.