Neurobehavioural effects of occupational exposure to lead.

A set of neurobehavioural tests selected on the basis of information processing theory was used to study the effect of low level occupational lead exposure on 59 lead workers compared with a matched control group of the same number. Only one of the lead exposed group had a blood lead concentration above the current threshold limit value of 3.81 mumol/l at the time of testing (mean 2.36 mumol/l, range 1.19-3.92 mumol/l) and none had been detected above that level in the previous three years. Nevertheless, most neurobehavioural functions tested showed some impairment in the lead workers. Visual sensory function was affected and, perhaps as a consequence, sustained attention and psychomotor tasks were performed more slowly by the lead exposed group. Cognitive functions were also impaired, with sensory store memory, short term memory, and learning abilities all showing deficits in lead workers. Such cognitive deficits may also be partly due to initial degradation of the visual input. Long term memory performance compared equally with control levels possibly because of development of a compensatory strategy such as rehearsal by the lead exposed subjects. Multiple linear regression analysis relating to lead workers test performance and their lead exposure showed that performance on the sensory store memory test alone was significantly related to exposure. This was probably due to the homogeneity of the lead exposed group with regard to blood lead concentrations and the use of blood lead as a measure of chronic lead exposure.

The acute effects of ethanol on auditory event-related potentials.

The acute effects of ethanol on the ERPs evoked by auditory stimuli were investigated using 0 g/kg, 0.3 g/kg and 0.54 g/kg ethanol dose. Ethanol was administered to 13 subjects single blind and orally in 20% v/v orange juice. Each subject received one of the three doses at three separate testing sessions. The ERPs were monitored at Cz in the 10-20 system in an odd ball paradigm. At the 0.54 g/kg ethanol level, an increase in latency was observed in the N1, P2, N2 components under both stimuli type conditions. The latency and amplitude of the P3 component were affected by ethanol at both dose levels. The amplitude of P3 was reduced and the latency increased in a dose-dependent manner. These characteristics of the P3 were observed under the target stimuli condition. The findings of the study suggested that stimulus attention, as reflected by N1 amplitude, was affected at the moderate ethanol dose level while stimulus categorisation, as reflected by P3 latency, was affected at the low ethanol dose level, with increased effects at the moderate dose level.

Occupational mercury exposure and its consequences for behaviour.

Mercury is a known neurotoxin. Evidence from animal studies show behavioural impairment which can be long-lasting, after low-level exposure to mercury. Human research, however, has not been conclusive. Chronic, high-level mercury exposure such as occurred in Japan, and the Middle East, Causes long-lasting and profound neurological damage. However the effects of low-level exposure, such as occurs in occupational exposure, are far from clear. This study used a comprehensive test battery based on an information processing framework to compare a group of twelve chronically mercury-exposed workers with a matched control group. The mercury-exposed group showed poorer psychomotor co-ordination and premature fatigue, although simple motor responses were not affected. General arousal levels also remained unaffected but mercury-exposed workers were superior in sustaining attention. In spite of this, the mercury-exposed group showed clear deficits in short-term memory.

Interaction between ethanol and antihistamines: 3. mebhydrolin.

We used 17 student volunteers in an experiment to investigate the effects of orally administered mebhydrolin (0.71 mg/kg), alone and in combination with ethanol (0.75 g/kg), on perceptual, cognitive and motor functions. Mebhydrolin did not significantly modify performance when given alone, but showed evidence of enhancing ethanol-induced performance deficits. Histamine challenge experiments indicated that the dose of mebhydrolin used exerted an antihistaminic effect over the period of the ethanol interaction study.

The effect of cannabidiol, alone and in combination with ethanol, on human performance.

Fifteen volunteers received cannabidiol (CBD) (320 microgram/kg) or placebo (both orally, T0), and 60 min later they consumed an ethanolic beverage (0.54 g/kg) or placebo. The effects were measured at T1 (100 min after CBD ingestion), T2 (160 min) and T3 (220 min) using cognitive, perceptual and motor function tests. Factorial analysis indicated that test procedures could be adequately expressed by three rotated factors: A reaction speed factor (I), a standing steadiness factor (II) and a psychomotor coordination/cognitive factor (III). Ethanol produced a significant decrement in factor III. There was no demonstrable effect of CBD, either alone or in combination with ethanol. Neither CBD nor ethanol produced any significant effect on pulse rate. Prior administration of CBD did not significantly affect the blood ethanol levels. Whilst the subjects were able to identify correctly when they were given ethanol, they did not report any subjective effects of CBD.

The effect of (-) trans-delta9-tetrahydrocannabinol, alone and in combination with ethanol, on human performance.

Twenty five volunteers received (-) trans-delta9-tetrahydrocannabinol (THC) (320 microgram/kg) or placebo (both orally, T0), and, 60 min later, they consumed an ethanolic beverage (0.54 g/kg) or placebo. The effects of this medication were measured at T1 (100 min after THC ingestion), T2 (160 min), T3 (220 min) and T4 (280 min) using a battery of cognitive, perceptual and motor function tests. Factorial analysis indicated that the test procedures could be adequately expressed by four rotated factors: a reaction speed factor (I'), a cognitive factor (II'), a standing steadiness factor (III') and a psychomotor coordination factor (IV'). The first principal component (I) was used as a measure of general performance across the whole test battery. Both THC and ethanol produced significant decrements in the general performance factor. Ethanol produced significant decrements in standing steadiness and psychomotor coordination, while THC caused a significant deterioration in performance on all the four rotated factors. In all cases the peak effect of ethanol occurred at T1 and by T4 the effect had worn off. The performance decrements induced by THC were slower in onset and lasted longer than those induced by ethanol. In general, the peak effect of THC occurred at T1 and T2. There was no evidence of any interaction between THC and ethanol, and the effects of a combination of THC and ethanol were no more than additive. THC (but not ethanol) produced a significant rise in pulse rate. Prior administration of THC did not significantly affect the blood ethanol levels obtained. The subjects were able to identify correctly which of the treatments they had received.

The interaction between ethanol and antihistamines: 2. Clemastine.

Eighty paid student volunteers (35 male, 45 female) were used in an experiment to investigate the effects of a therapeutic dose of clemastine (1 mg) alone and in combination with a social dose of ethanol (0.54 g/kg) on perceptual, cognitive and motor functions. Both drugs were given orally. Clemastine did not significantly modify performance when given alone, and the performance decrements induced by ethanol were not enhanced by clemastine premedication.

The interaction between ethanol and antihistamines. 1: Dexchlorpheniramine.

Thirteen paid student volunteers (9 male, 4 female) were used in a double-blind crossover experiment to investigate the effects of a therapeutic dose of dexchlorpheniramine alone, and in combination with a social dose of ethanol on perceptual, cognitive and motor functions. Both ethanol (0.75 g/kg) and dexchlorpheniramine (4 mg/70 kg) were given orally. Although a synergistic effect of dexchlorpheniramine with ethanol was only observed in some of the tests, a delayed recovery from the effects of the combination was noted. Subjective data indicated that the sedative effects of dexchlorpheniramine were more pronounced in the presence of ethanol.

Ethanol and delta9-tetrahydrocannabinol interactive effects on human perceptual, cognitive and motor functions. II.

Fifteen paid student volunteers (10 male, five female) were used in a double-blind crossover experiment to further investigated the effects of delta9-tetrahydrocannabinol (THC), alone and in combination with ethanol, on perceptual, cognitive and motor functions. Both ethanol (0-54 g/kg) and THC (15 MG/70 KG) WERE GIVEN ORALLY. Ethanol was not very effective in in+uencing performance but this dose of THC produced marked decrements, predominantly in the latter part of the experiment. When they were given together, an early additive effect was apparent, but later, there was a suggestion of antagonism in that subjects who received the drug combination performed better than those who were given THC along. The interaction between THC and ethanol was considered to be complex.

The interaction of ethanol and delta9-tetrahydrocannabinol in man: effects on perceptual, cognitive and motor functions.

Twelve paid student volunteers (8 male, 4 female) were used in a double-blind crossover experiment to investigate the effects of delta9-tetrahydrocannabinol (THC) alone, and in combination with ethanol, on human perceptual, cognitive and motor functions. Both THC (10 mg/70 kg) and ethanol (0-5 g/kg) had little effect when administered alone. The combination of drugs, however, induced a significnat decrement in performance in some of the tests and this interaction was considered to be at least additive. The peak blood ethanol concentration was higher (P = 0-05) when subjects received both ethanol and THC than when they received ethanol alone.

The effect of disodium cromoglycate on human performance, alone and in combination with ethanol.

Seventeen paid volunteer subjects were used in a double-blind crossover experiment to investigate the effects of disodium cromoglycate (DSCG), alone and in combination with ethanol, on human perceptual, cognitive and motor performance. DSCG (40 mg) had little effect when given alone. When administered with ethanol (0-75 g/kg), DSCG did not significantly modify the ethanol-induced decrement in performance except in the complex reaction time test.

The relationship between alcohol dosage and performance decrement in humans.

The effects of alcohol on human perceptual, cognitive and motor performance was assessed in a battery of tests, and the dose-response relationships for alcohol, important for the study of drug-alcohol interactions, established.