Assessment of GABA(A)benzodiazepine receptor (GBzR) sensitivity in patients on benzodiazepines

Effect of midazolam in autism spectrum disorder: A retrospective observational analysis

BACKGROUND

While midazolam is commonly used as premedication for uncooperative patients, its effects are difficult to predict in patients with autism spectrum disorder for whom abnormalities in gamma-aminobutyric acid have been reported. This study aimed to investigate the influence of autism spectrum disorder on the effect of midazolam when used as premedication.

METHODS

This retrospective observational study was performed between April 2017 and August 2018. Before inducing general anesthesia with sevoflurane for dental treatment, 390 uncooperative patients received premedication with midazolam. Ordinal logistic regression analysis was performed with the Observer's Assessment of Alertness/Sedation score 30 min after premedication as the objective variable. Age, sex, American Society of Anesthesiologists physical status class, premedication route, dose per body weight, presence of specific disorders (autism spectrum disorder, intellectual disability, epilepsy, cerebral palsy, and other psychiatric disorders), and regular benzodiazepine or non-benzodiazepine psychotropic administration were included as explanatory variables. Kendall's rank correlation coefficient was used to assess the correlation between the Observer's Assessment of Alertness/Sedation score and cooperation level (1, obvious negative response; 2, negative response; 3, positive reaction; 4, obvious positive reaction) during admission and inhalation induction. All data were extracted from anesthesia and medical records.

RESULTS

Age (odds ratio 1.437 [95% confidence interval (CI) 1.213-1.708], P < .001), autism spectrum disorder (1.318 [1.079-1.612], P = .007), benzodiazepine medication (0.574 [0.396-0.827], P = .002), and intramuscular route (1.478 [1.137-1.924], P = .004) were significantly associated with the Observer's Assessment of Alertness/Sedation score, while the score was negatively associated with cooperation levels during admission (τ = -0.714, P < .001) and inhalation induction (τ = -0.606, P < .001).

CONCLUSIONS

Patients with autism spectrum disorder may be susceptible to premedication with midazolam; however, regular benzodiazepine administration may reduce the effect.

Treating anxiety complicated by substance misuse

The relationship between anxiety disorders and substance misuse is intimate. Here we concentrate on alcohol, although for completeness we also briefly mention other substances taken for anxiety relief or that cause anxiety.

An anxiety-like phenotype in mice selectively bred for aggression

Using selective bi-directional breeding procedures, two different lines of mice were developed. The NC900 line is highly reactive and attacks their social partners without provocation, whereas aggression in NC100 animals is uncommon in social environments. The enhanced reactivity of NC900 mice suggests that emotionality may have been selected with aggression. As certain forms of anxiety promote exaggerated defensive responses, we tested NC900 mice for the presence of an anxiety-like phenotype. In the open field, light-dark exploration, and zero maze tests, NC900 mice displayed anxiety-like responses. These animals were less responsive to the anxiolytic actions of diazepam in the zero maze than NC100 animals; diazepam also reduced the reactivity and attack behaviors of NC900 mice. The NC900 mice had reduced diazepam-sensitive GABA(A) receptor binding in brain regions associated with aggression and anxiety. Importantly, there was a selective reduction in levels of the GABA(A) receptor alpha(2) subunit protein in NC900 frontal cortex and amygdala; no changes in alpha(1) or gamma(2) subunit proteins were observed. These findings suggest that reductions in the alpha(2) subunit protein in selected brain regions may underlie the anxiety and aggressive phenotype of NC900 mice. Since anxiety and aggression are comorbid in certain psychiatric conditions, such as borderline personality and posttraumatic stress disorder, investigations with NC900 mice may provide new insights into basic mechanisms that underlie these and related psychiatric conditions.

Assessment of GABAA benzodiazepine receptor (GBzR) sensitivity in patients with alcohol dependence

AIM

The aim of this study was to measure GABAA benzodiazepine receptor (GBzR) sensitivity in alcohol-dependent patients and compare with matched non-dependent drinkers.

METHODS

Nine abstinent alcohol-dependent male patients, age matched with nine male non-dependent social drinkers, received an intravenous infusion of midazolam. Objective (saccadic eye movement slowing) and subjective (visual analogue scales) measurements were recorded at 15-min intervals for 2 h.

RESULTS

There were no differences in objective or subjective measures.

CONCLUSIONS

Our hypothesis that patients with alcohol dependence would have less slowing of their eye movements in response to this challenge, reflecting reduced GBzR sensitivity, was not confirmed. The reasons for this could mean that GBzR function returns to normal with abstinence, or that this paradigm is unable to measure the subtle subtype-specific changes in GBzR sensitivity that occur following dependent alcohol use.

Saccadic eye velocity after selective GABAergic treatment with tiagabine in healthy volunteers

BACKGROUND

Saccadic eye velocity (SEV) has been shown to be a reliable neurophysiological tool for the assessment of gamma-aminobutyric acid GABA(A) receptor sensitivity. Administration of benzodiazepines targeting the GABA(A) receptor decreases SEV in healthy volunteers. Tiagabine is a new antiepileptic drug which acts via selective blockade of GABA reuptake. Therefore, we examined the effects of tiagabine on saccade parameters.

METHODS

SEV was analyzed in 8 healthy volunteers before and after 7 days of tiagabine treatment. Subjects received tiagabine in a daily dose of 15 mg. Saccades were measured using a noninvasive infrared oculographic device. Amplitude, latency, and SEV were analyzed as a function of treatment and target eccentricity.

RESULTS

SEV and saccade latency increased with target amplitude. Treatment with tiagabine had no significant effect on SEV and saccade amplitude. A trend was found for increased latencies after tiagabine.

CONCLUSION

In contrast to findings with benzodiazepines, tiagabine treatment had no impact on SEV in healthy volunteers. The subchronic tolerance effects or the different site of action on the GABA(A)/BZD receptor complex may account for this deviating profile.

GABAAbenzodiazepine receptor (GBzR) sensitivity: test-retest reliability in normal volunteers

Rationale: Alcohol, benzodiazepines and barbiturates act through the GABA(A) benzodiazepine receptor (GBzR). Patients with some forms of anxiety disorder have reduced GBzR sensivity, although it is not clear whether this is a state or a trait phenomenon. We have developed a paradigm for assessing GBzR sensitivity using slowing of saccadic eye movements in response to intravenous midazolam.Objectives: To obtain reliability data for GBzR sensitivity in normal volunteers and to look at factors that might influence sensitivity.Methods: Five male volunteers received an intravenous infusion of midazolam (50 &mgr;m/kg) given over 10 min. Saccadic eye movement velocity (SEMV) was recorded at baseline and at 15 min intervals up to 120 min post infusion. Blood was taken at these times for mixazolam assay. The study was repeated at 4 weeks. Pharmacodynamic (PD) effect was calculated by measuring area under the curve (AUC) of SEMV plot versus time for each individual on both study days. Pharmacokinetic (PK) effect was calculated by measuring AUC from t = 0 to t = 120 min. Ratio of PD/PK effect was then calculated to give a measure of GBzR sensitivity.Results: There was a very strong correlation between individual GBzR sensitivity on both study days (r = 0.99; p = 0.008).Conclusion: The results suggest that GBzR sensitivity is relatively stable over time in normal volunteers and that the paradigm described has good reliability. Copyright 2000 John Wiley & Sons, Ltd.