June M. Stapleton

Higher levels of nicotine in arterial than in venous blood after cigarette smoking

We examined differences between arterial and venous concentrations of nicotine in human subjects. Shortly after smoking a cigarette, levels of nicotine in arterial plasma were more than double those in venous plasma. The time course of the rise in arterial nicotine levels and the magnitude of the arteriovenous difference varied considerably among subjects. For some subjects, arterial nicotine concentrations after one cigarette were similar to venous concentrations typically observed after 20 cigarettes and were nearly 10 times greater than venous concentrations. Our findings have implications for understanding the high degree of addictiveness and cardiovascular toxicity of smoked forms of drugs.

Cerebral glucose utilization is reduced in second test session

Cerebral glucose utilization was higher during the first positron emission tomography (PET) session than during the second session, as assayed using the PET [18F]fluorodeoxyglucose method in male human volunteers. This difference was due largely to data from subjects with low trait anxiety, since subjects with high anxiety showed similar metabolism in both PET sessions. High-anxiety subjects showed greater right/left ratios of cerebral metabolism than low-anxiety subjects, particularly during the second PET session. These findings suggest that the level of anxiety may be an important variable to consider in PET studies using multiple sessions.

Dose-related effects of ethanol on visual sustained attention and event-related potentials

The effects of acute ethanol intoxication on visual sustained attention were investigated in male social drinkers. Four doses ranging from 0 (placebo) to 1.05 g/kg lean body weight, with periodic maintenance dosing of 0.12 g/kg, were given in separate sessions. The task required subjects to monitor a series of blurred digits presented singly at a rate of one per sec and to respond to occasional (p = 0.25) target digits with a speeded button press. Detection performance deteriorated as a function of both dose and time on task. In addition, the factors of dose and time on task interacted to produce a more rapid performance decrement under the higher doses. Early event-related potential (ERP) components (N1 and P2) were not greatly affected, suggesting that the performance decrement reflects central rather than peripheral factors. Later components related to cognitive appraisal processes (N2, P3), in contrast, varied in both amplitude and latency. Ethanol yielded dose-related delays in N2 and P3 latencies, which paralleled reaction time increases. The amplitude of N2 also decreased over time on task, and P3 amplitude decreased both as a function of dose and time on task. ERP and performance data were interpreted as demonstrating an adverse effect of ethanol on central processing capacity.

Alcohol intoxication reduces visual sustained attention

Effects of alcohol intoxication on visual sustained attention were studied using a vigilance task entailing detection of degraded target stimuli. Data were obtained in separate sessions under four ethanol doses, ranging from 0 (placebo) to 1.05 g/kg lean body weight, with periodic maintenance dosing of 0.12 g/kg. Intoxication lowered the overall level of detection performance, and in addition produced dose-related increases in the rate of performance decrement over time. Analysis of performance data using techniques derived from Signal Detection Theory indicated that the decrements were due specifically to alterations in perceptual sensitivity. Examination of eye movements and blinks indicated that the effects of ethanol were not mediated peripherally. Rather, alcohol appears to have deleterious effects on central processing capacity and the availability of capacity over time. The alcohol-related failure of sustained attention may contribute to increased accident risk in tasks requiring continuous performance.

Cerebral Glucose Utilization in Polysubstance Abuse

Regional cerebral glucose metabolism in subjects with histories of polysubstance abuse was compared to that in control subjects who were drawn from the same community. The substance abuse group showed lower absolute metabolic rates for glucose in lateral occipital gyrus and higher normalized metabolic rates in temporal and frontal areas, including orbitofrontal cortex. It is suggested that some patterns of brain function associated with polysubstance abuse may represent consequences of drug exposure, or they could reflect pre-existing differences that may be relevant to the etiology and maintenance of polysubstance abuse.

Effects of adinazolam and diazepam, alone and in combination with ethanol, on psychomotor and cognitive performance and on autonomic nervous system reactivity in healthy volunteers

SummaryEffects on psychomotor and cognitive performance of adinazolam (15 or 30 mg), alone and in combination with ethanol (0.8 g/kg), were studied in healthy male volunteers and compared to effects of 10 mg diazepam.Adinazolam 30 mg produced relatively long-lasting impairments on tests of tracking, attention, verbal and nonverbal information processing, and memory. Adinazolam 15 mg resulted in descreased visual information processing. Adinazolam decreased supine mean arterial pressure, but only the 15 mg resulted in a tendency for decreased plasma norepinephrine concentrations.After standing for 5 min, 30 mg adinazolam was associated with increased heart rate.Although ethanol consumption produced additive decrements on a continuous performance task, there was little evidence to support a synergistic effect.Adinazolam 30 mg was accompanied by increased self-reports of side effects, especially drowsiness.

Subjective and cardiovascular effects of intravenous nicotine in smokers and non-smokers

Abstract The present study assessed the subjective and cardiovascular effects of intravenous nicotine in smokers and nonsmokers. Nonsmokers (n = 5) and smokers (n = 5) were administered a single dose of nicotine (0.75 or 1.5 mg) or saline on each of 3 days. The nicotine doses were given in ascending order in a double-blind fashion. Although smokers and nonsmokers manifested significant increases in systolic and diastolic blood pressure and heart rate 1 min after administration of all active test doses, the difference between peak heart rate and that measured at later times was greater in nonsmokers than in smokers. Nonsmokers and smokers also differed in subjective self-reports. In response to items on visual analogue scales indicative of positive effects (e.g., “good effects,”“like drug,”“use again,” and “feel energetic”), smokers but not nonsmokers reported high scores (> 40) after nicotine injection. In addition, responses on the MBG and LSD subscales of the Addiction Research Center Inventory indicated that smokers experienced positive subjective effects after the test doses, whereas nonsmokers experienced disorientation. The fact that intravenous nicotine was not associated with positive subjective effects in nonsmokers indicates that repeated exposure is required to establish positive reinforcing effects of nicotine.

Intravenous nicotine reduces cerebral glucose metabolism: a preliminary study.

Nicotine is self-administered by smoking tobacco products, and enhances positive mood (at least in smokers). Since most drugs of abuse decrease regional cerebral metabolic rate(s) for glucose (rCMRglc) in human subjects, we posited that administration of nicotine would similarly reduce rCMRglc. Positron emission tomography (PET) with [F-18]fluorodeoxyglucose was used to assess the effects of intravenous nicotine (1.5 mg) on cerebral glucose metabolism in six healthy male volunteers (21–38 years of age). Two PET assays (placebo and nicotine) were performed, and subjective self-reports of mood and feeling state were collected. Data were analyzed using analysis of variance. Nicotine reduced global glucose metabolism (by 9.51% of placebo control), with reductions in most of the 30 individual regions tested. Nine regions had bilateral effects that reached statistical significance (p<0.05, uncorrected for the number of regions tested), although the statistical model used did not separate these effects from a global effect. The subjects reported both positive and negative effects of nicotine on mood/feeling state. The widespread decreases in cerebral metabolism are consistent with the many effects of nicotine on cognition and mood. The findings indicate that nicotine resembles other drugs of abuse in reducing brain metabolism, perhaps by a common mechanism.

Effects of fluvoxamine, alone and in combination with ethanol, on psychomotor and cognitive performance and on autonomic nervous system reactivity in healthy volunteers

The effects of fluvoxamine (50 or 100 mg), alone and in combination with ethanol (0.8 g/kg), on psychomotor and cognitive performance and on autonomic nervous system reactivity were studied in healthy male volunteers. Fluvoxamine produced neither serious psychomotor or cognitive impairment nor alterations in autonomic nervous system functioning at these doses. There was no evidence that fluvoxamine exacerbated, or improved, ethanol-induced impairments of memory or any other measures evaluated. Fluvoxamine tended to improve recognition, but not free recall, of words.

Fluvoxamine treatment of alcoholic amnestic disorder

The serotonin uptake inhibitor fluvoxamine was assessed in treatment of alcohol-induced Korsakoffs syndrome (KS) using fixed (4 weeks, 200 mg/day) or individualized (6 weeks, plasma concentration > or = 400 ng/ml) dosing in randomized placebo-controlled double-blind crossover studies. Cognitive functions and concentrations of the major cerebrospinal fluid (CSF) metabolites of serotonin (5-HIAA), norepinephrine (MHPG), and dopamine (HVA) were determined in abstinent, nondepressed KS patients (aged 45-75), at baseline and placebo (3-4 weeks), and after 3-4 (n = 10) or 6 (n = 4) weeks of fluvoxamine administration. Fluvoxamine decreased CSF 5-HIAA compared to placebo (P < 0.003) without consistent changes in HVA or MHPG. Reductions in 5-HIAA correlated with improvements on the Wechsler Memory Scale Memory Quotient (P < 0.05), independent of effects on attention/vigilance or Beck Depression Inventory scores. Reductions in 5-HIAA correlated with plasma fluvoxamine (P < 0.03) only for fluvoxamine concentrations below 450 ng/ml. These findings suggest improvement of memory consolidation and/or retrieval in patients with Korsakoffs syndrome by fluvoxamine via serotonergic mechanisms.