Lorazepam and diazepam differently impair divided attention

GABAergic modulation of performance in response inhibition and interference control tasks

BACKGROUND

Inhibitory control is a crucial executive function with high relevance to mental and physical well-being. However, there are still unanswered questions regarding its neural mechanisms, including the role of the major inhibitory neurotransmitter, γ-aminobutyric acid (GABA).

AIMS

This study examined the effects of lorazepam (0.5 mg and 1 mg), a positive allosteric modulator at the GABA_A receptor, on response inhibition and interference control. We also explored the heterogeneity of inhibitory control and calculated delta plots to explore whether lorazepam affects the gradual build-up of inhibition and activation over time.

METHODS

N = 50 healthy participants performed antisaccade, Eriksen flanker and Simon tasks in a within-subjects, placebo-controlled, double-blind randomized design.

RESULTS

Lorazepam increased reaction time (RT) and error rates dose dependently in all tasks (p ⩽ 0.005). In the antisaccade and Simon tasks, lorazepam increased congruency effects for error rate (p ⩽ 0.029) but not RT (p ⩾ 0.587). In the Eriksen flanker task, both congruency effects were increased by the drug (p ⩽ 0.031). Delta plots did not reflect drug-induced changes in inhibition and activation over time. Delta plots for RT in the Simon task were negative-going, as expected, whereas those for the antisaccade and flanker tasks were positive-going.

CONCLUSIONS

This study provides evidence for GABAergic involvement in performance on response inhibition and interference control tasks. Furthermore, our findings highlight the diversity of the broader construct of inhibitory control while also pointing out similarities between different inhibitory control tasks. In contrast to RT and error rates, the cognitive processes indexed by delta plots may not be sensitive to GABAergic modulation.

Muscarinic M1, but not M4, receptor antagonism impairs divided attention in male rats

Divided attention may be more important than ever to comprehend, given ubiquitous distractors in modern living. In humans, concern has been expressed about the negative impact of distraction in education, the home, and the workplace. While acetylcholine supports divided attention, in part via muscarinic receptors, little is known about the specific muscarinic subtypes that may contribute. We designed a novel, high-response rate test of auditory sustained attention, in which rats complete variable-ratio runs on one of two levers, rather than emitting a single response. By doing this, we can present a secondary visual distractor task during some trials, for which a correct nosepoke response is reinforced with a more palatable food pellet. The nonspecific muscarinic antagonist scopolamine impaired performance, and slowed and reduced lever press activity. We then explored antagonists that preferentially block the M1 and M4 subtypes, because these receptors are potential therapeutic targets for cognitive enhancers. Telenzepine, an M1-preferring antagonist, impaired divided attention performance, but not performance of the attention task without distraction. Telenzepine also had fewer nonspecific effects than scopolamine. In contrast, the M4-preferring antagonist tropicamide had no effects. Analysis of overall behavior also indicated that accuracy in the main attention task decreased as a function of engagement with the distractor task. These results implicate the M1 receptor in divided attention.

Conversion factors for assessment of driving impairment after exposure to multiple benzodiazepines/z-hypnotics or opioids

AIMS

Norway has introduced legal concentration limits in blood for 28 non-alcohol drugs in driving under the influence cases. As of 2016 this legislation also regulates the assessment of combined effects of multiple benzodiazepines and opioids. We herein describe the employed methodology for the equivalence tables for concentrations of benzodiazepines/z-hypnotics and opioids implemented in the Norwegian Road Traffic Act.

METHODS

Legislative limits corresponding to impairment at blood alcohol concentrations (BAC) of 0.02%, 0.05% and 0.12% were established for 15 different benzodiazepines and opioids. This was based on a concept of a linear relationship between blood drug concentration and impairment in drug naïve users. Concentration ratios between these drugs were used to establish conversion factors and calculate net impairment using diazepam and morphine equivalents.

RESULTS

Conversion factors were established for 14 benzodiazepines/z-hypnotics (alprazolam, bromazepam, clobazam, clonazepam, etizolam, flunitrazepam, lorazepam, nitrazepam, nordiazepam, oxazepam, phenazepam, temazepam, zolpidem and zopiclone) and two opioids (methadone and oxycodone).

CONCLUSIONS

Conversion factors to calculate diazepam and morphine equivalents for benzodiazepines/z-hypnotics and selected opioids, respectively, have been operative in the Norwegian Road Traffic Act as of February 2016. Calculated equivalents can be applied by the courts to meter out sanctions.

Central nervous system effects of alcohol at a pseudo-steady-state concentration using alcohol clamping in healthy volunteers

AIM

In determining the acute effects of alcohol, it is helpful if alcohol concentrations are maintained at stable levels, to facilitate the interpretation of the results. Recently, an alcohol clamping method was developed that resulted in stable alcohol concentrations for hours. The aim of this study was to test a range of central nervous system (CNS) effects under pseudo-steady-state conditions.

METHODS

To achieve a pseudo-steady state of 0.6 g l(-1), breath alcohol concentrations (BrAC) were frequently measured and fed back into a spreadsheet-based program to guide intravenous dosing. CNS effects were frequently measured throughout the clamp.

RESULTS

The clamping paradigm resulted in a pseudo-steady-state BrAC of 0.61 g l(-1) (coefficient of variation 6.2%). A plateau was maintained from 25 to 300 min and caused significant effects on smooth pursuit eye movements [-9.7%, 95% confidence interval (CI) -12.4, -7.1], adaptive tracking (-3.4%, 95% CI -4.5, -2.2), visual analogue scale (VAS) alertness (-13 mm, 95% CI -20, -6), VAS alcohol effects (16 mm, 95% CI 7, 25) and body sway (21.3%, 95% CI 1.8, 45). Some effects (like smooth pursuit eye movements) closely followed the relatively stable alcohol concentrations, whereas others (such as body sway and VAS alcohol effects) fluctuated during the plateau phase.

CONCLUSIONS

Most CNS effects of alcohol showed a trend to change over time, despite stable concentrations. Other variables remained stable under pseudo-steady-state conditions. The intravenous clamping method provides precise control over BrAC levels and allows frequent repetition of different CNS measurements. These features make this technique eminently suitable to study the complex pharmacodynamic effects of acute alcohol administration.

The effects of lorazepam on skin conductance responses to aversive stimuli in healthy subjects

BACKGROUND

Autonomic responses to aversive stimuli are widely used to model anxiolytic drug effects in healthy humans. Benzodiazepine anxiolytics dose dependently attenuate autonomic responses to aversive stimuli by their anxiolytic as well as sedative action. The present study aimed to examine the effects of non-sedative doses of lorazepam on skin cutaneous responses to aversive stimuli and subjective mood.

METHODS

A randomized, double blind, cross over study of 12 healthy male volunteers aged 24 years (23-32; median; range) was carried out. Subjects received single oral doses of 0.5 and 1.0 mg lorazepam as well as placebo on three different occasions with at least 5 days in-between. Skin conductance responses (SCRs) to unpleasant pictures and noises, pupillary unrest index as well as subjective levels of anxiety were measured repeatedly before and after drug administration.

RESULTS

SCRs were found significantly lower 2 hours following ingestion of 0.5 mg lorazepam as well as 1, 2 and 3 hours after 1.0 mg lorazepam were given as compared to baseline conditions. By contrast, administration of placebo did not influence SCRs to a significant extent. Both doses of lorazepam did not change pupillary unrest index nor subjective mood.

CONCLUSIONS

Lorazepam may attenuate SCRs to aversive stimuli without affecting vigilance nor subjective mood. Attenuation of autonomic responses to aversive stimuli may not be specific for an anxiolytic effect.

Veränderte Aufmerksamkeit unter dem Benzodiazepin Lorazepam

Zusammenfassung: Aus der klinischen Praxis und einigen experimentellen Studien ergaben sich Hinweise, dass unter dem Einfluss von Benzodiazepinen Einschränkungen der Aufmerksamkeit auftreten können. In der vorliegenden Studie wurde der Frage nachgegangen, welche Komponenten der Aufmerksamkeit durch die Wirkung von Lorazepam beeinträchtigt werden. In einer placebo-kontrollierten Doppel-Blind-Studie mit 20 gesunden Probanden wurden folgende funktionelle Komponenten der Aufmerksamkeit 3 Stunden nach Einnahme von Lorazepam (p.o. 0.02mg/kgKörpergewicht) untersucht: Informationsverarbeitungsgeschwindigkeit, selektive Aufmerksamkeit, Daueraufmerksamkeit, geteilte Aufmerksamkeit und Aufmerksamkeitswechsel. Die Reaktions- bzw. Verarbeitungsgeschwindigkeit waren in allen verwendeten Verfahren mit Ausnahme der geteilten Aufmerksamkeit unter der Wirkung von Lorazepam signifikant erniedrigt. Hinsichtlich von Treffer- bzw. Fehlerraten war dagegen kein signifikanter Unterschied zwischen Lorazepam und Placebo zu beobachten. Die Wirkung von Benzodiazepinen scheint wenig selektiv bezüglich der verschiedenen Aufmerksamkeitskomponenten zu sein. Es kommt offenbar nach Benzodiazepin-Einnahme zu einer generalisierten Verlangsamung der Informationsverarbeitung.

Are lorazepam-induced deficits in attention similar to those resulting from aging?

The purpose of this experiment was to compare, in three tasks of attention, the impairment caused by lorazepam (1 and 2.5 mg) administered to young volunteers with the impairment that results from aging. Performance on digit cancellation (DC), digit-symbol substitution (DSS), and Paced Auditory Serial Addition Task (PASAT) was significantly impaired by lorazepam (2.5 mg) and was significantly worse in the middle-aged group (mean +/- SEM, aged 58.9+/-0.8 years) compared with the younger, IQ-matched group (20.7+/-0.2 years). However, there were interesting differences in the extent of impairments among the three tests. In the DC test, lorazepam (2.5 mg) produced a significantly greater impairment than was seen in either the middle-aged men or middle-aged women. However, in the DSS test, the middle-aged women were significantly more impaired than either the middle-aged men or the young volunteers tested after lorazepam (2.5 mg). In the PASAT, both the lorazepam (2.5 mg) group and the middle-aged women were more impaired than the middle-aged men. These results raise the important possibility of gender differences in age-related decline of attentional processes.