Oxazepam and cognitive reappraisal: A randomised experiment

Background

Cognitive reappraisal is a strategy for emotional regulation, important in the context of anxiety disorders. It is not known whether anxiolytic effects of benzodiazepines affect cognitive reappraisal.

Aims

We aimed to investigate the effect of 25 mg oxazepam on cognitive reappraisal.

Methods

In a preliminary investigation, 33 healthy male volunteers were randomised to oxazepam or placebo, and then underwent an experiment where they were asked to use cognitive reappraisal to upregulate or downregulate their emotional response to images with negative or neutral emotional valence. We recorded unpleasantness ratings, skin conductance, superciliary corrugator muscle activity, and heart rate. Participants completed rating scales measuring empathy (Interpersonal Reactivity Index, IRI), anxiety (State-Trait Anxiety Inventory, STAI), alexithymia (Toronto Alexithymia Scale-20, TAS-20), and psychopathy (Psychopathy Personality Inventory-Revised, PPI-R).

Results

Upregulation to negative-valence images in the cognitive reappraisal task caused increased unpleasantness ratings, corrugator activity, and heart rate compared to downregulation. Upregulation to both negative- and neutral-valence images caused increased skin conductance responses. Oxazepam caused lower unpleasantness ratings to negative-valence stimuli, but did not interact with reappraisal instruction on any outcome. Self-rated trait empathy was associated with stronger responses to negative-valence stimuli, whereas self-rated psychopathic traits were associated with weaker responses to negative-valence stimuli.

Conclusions

While 25 mg oxazepam caused lower unpleasantness ratings in response to negative-valence images, we did not observe an effect of 25 mg oxazepam on cognitive reappraisal.

Is the unique benzodiazepine structure interacting with CYP enzymes to affect steroid synthesis in vitro?

The aim of this project was to investigate the endocrine disrupting effects of three γ-aminobutyric acid type A receptor (GABA_AR) agonists, diazepam (DZ), oxazepam (OX) and alprazolam (AL) using the steroidogenic in vitro H295R cell line assay, a recombinant CYP17A1 assay, qPCR analysis and computational modelling. Similar effects for DZ and OX on the steroidogenesis were observed in the H295R experiment at therapeutically relevant concentrations. Progestagens and corticosteroids were increased up to 10 fold and androgens were decreased indicating CYP17A1 lyase inhibition. For DZ the inhibition on both the hydroxylase and lyase was confirmed by the recombinant CYP17A1 assay, whereas OX did not appear to directly affect the recombinant CYP17A1 enzyme. Androgens were decreased when exposing the H295R cells to AL, indicating a CYP17A1 lyase inhibition. However, this was not confirmed by the recombinant CYP17A1 assay but a down-regulation in gene expression was observed for StAR and CYP17A1. The present study showed that the three investigated benzodiazepines (BZDs) are rather potent endocrine disruptors in vitro, exerting endocrine effects close the therapeutic C_max. Both direct and indirect effects on steroidogenesis were observed, but molecular modelling indicated no direct interactions between the heme group in the steroidogenic CYP enzymes and the unique diazepin structure. In contrast, physicochemical properties such as high log P, structure and molecular weight similar to that of steroids appeared to influence the endocrine disrupting abilities of the investigated pharmaceuticals in vitro. Docking of the three BZDs in CYP17A1 and CYP21A2 confirmed that shape complementarity and hydrophobic effects seem to determine the binding modes.

The differential effects of alprazolam and oxazepam on methamphetamine self-administration in rats

BACKGROUND

Methamphetamine is the second most commonly used illicit drug in the world, and despite recent attempts by the Drug Enforcement Administration to combat this epidemic, methamphetamine use is still on the rise. As methamphetamine use increases so does polydrug use, particularly that involving methamphetamine and benzodiazepines. The present study was designed to examine the effects of two benzodiazepines on methamphetamine self-administration.

METHODS

Five doses of methamphetamine (0.0075, 0.015, 0.03, 0.09, and 0.12mg/kg/infusion) were tested, producing an inverted U-shaped dose-response curve. Rats were then pretreated with oxazepam, alprazolam, or vehicle prior to methamphetamine self-administration. To determine if the effects of these drugs were due to the GABAA receptor and/or translocator protein (TSPO), we also pretreated rats with an antagonist for the benzodiazepine-binding site on the GABAA receptor (i.e., flumazenil) and a TSPO antagonist (i.e., PK11195) prior to alprazolam or oxazepam administration.

RESULTS

Oxazepam significantly reduced methamphetamine self-administration as demonstrated by a downward shift of the dose-response curve. In contrast, alprazolam significantly enhanced methamphetamine self-administration as evidenced by a leftward shift of the dose-response curve. Flumazenil completely blocked the effects of alprazolam on methamphetamine self-administration. When administered individually, both flumazenil and PK11195 partially reversed the effects of oxazepam on methamphetamine self-administration. However, when these two antagonists were combined, the effects of oxazepam were completely reversed.

CONCLUSIONS

The GABAA receptor is responsible for the alprazolam-induced enhancement of methamphetamine self-administration, while the activation of both the GABAA receptor and TSPO are responsible for the oxazepam-induced reduction of methamphetamine self-administration.

Effect of active metabolites of chlordiazepoxide and diazepam, alone or in combination with alcohol, on psychomotor skills related to driving

The interaction of the main metabolites of diazepam and chlordiazepoxide with alcohol was measured in two double-blind crossover subacute experiments on 40 healthy young volunteers. The drugs were administered for 2 weeks each. The variables measured were choice reaction time and accuracy, eye-hand coordination, divided attention, flicker fusion, proprioception, and nystagmus. ChL, MO and O significantly enhanced the alcohol-induced impairment of psychomotor skills whereas DMD did so only exceptionally on some subjects in the choice reaction test. It is concluded that the diazepam-alcohol interaction on psychomotor skills is mainly due to the parent compound. No correlations between the serum levels of the agents and the changes of performance were found.

Ecological effects of pharmaceuticals in aquatic systems--impacts through behavioural alterations

The study of animal behaviour is important for both ecology and ecotoxicology, yet research in these two fields is currently developing independently. Here, we synthesize the available knowledge on drug-induced behavioural alterations in fish, discuss potential ecological consequences and report results from an experiment in which we quantify both uptake and behavioural impact of a psychiatric drug on a predatory fish (Perca fluviatilis) and its invertebrate prey (Coenagrion hastulatum). We show that perch became more active while damselfly behaviour was unaffected, illustrating that behavioural effects of pharmaceuticals can differ between species. Furthermore, we demonstrate that prey consumption can be an important exposure route as on average 46% of the pharmaceutical in ingested prey accumulated in the predator. This suggests that investigations of exposure through bioconcentration, where trophic interactions and subsequent bioaccumulation of exposed individuals are ignored, underestimate exposure. Wildlife may therefore be exposed to higher levels of behaviourally altering pharmaceuticals than predictions based on commonly used exposure assays and pharmaceutical concentrations found in environmental monitoring programmes.

The putative tumor suppressor Tsc-22 is downregulated early in chemically induced hepatocarcinogenesis and may be a suppressor of Gadd45b

Tsc-22 is a novel tumor suppressor gene that represents a new class of transcription factors that has transcriptional repressor activity. We found Tsc-22 downregulation in livers from B6C3F1 mice following treatment for 2 weeks with carcinogenic doses of the antianxiety drug oxazepam (2500 ppm) or the peroxisome proliferator Wyeth-14,643 (500 ppm) but not with two other carcinogens such as o-nitrotoluene or methyleugenol or three noncarcinogens including p-nitrotoluene, eugenol, or acetaminophen. The expression of Tsc-22 was also repressed in B6C3F1 mouse liver tumors that were induced by several chemicals from 2-year carcinogenicity studies as well as in spontaneous liver tumors. To identify potential Tsc-22 target genes in mouse liver, we transfected small interference RNA (SiRNA) designed to inhibit Tsc-22 into murine liver BNL-CL.2 cells. We selected two potential transcriptional targets of Tsc-22, growth arrest and DNA damage-inducible gene 45 beta (Gadd45b) and leucine zipper, putative tumor suppressor 2 (Lzts2) to test based on our previous complementary DNA microarray studies, showing that expression of these cancer-associated genes was increased when Tsc-22 was repressed. SiRNA treatment of BNL-CL.2 cells with Tsc-22 oligonucleotides but not nonspecific oligonucleotides decreased RNA and protein expression of Tsc-22 by 80-90%, while expression of Gadd45b gene, but not Lzts2, was increased over time after an initial decrease. Treatment of these cells with oxazepam for 48 h also resulted in decreased Tsc-22 and increased Gadd45b expression. These data provide evidence that Tsc-22 is a suppressor of Gadd45b expression, which may contribute to an early antiapoptotic response.

Pharmacological analysis of the effects of benzodiazepines on punished schedule-induced polydipsia in rats

Food-deprived Wistar rats were exposed to a fixed-time 60-s food delivery schedule until they developed schedule-induced polydipsia. Every fifth lick was then followed by an electric shock during two, signalled, 5-min periods, which ran concurrently with the food delivery schedule. Shock intensities were adjusted to reduce licking to 60-70% of the unpunished licking rates. The benzodiazepine full agonists, diazepam (0.3-3.0 mg/kg), chlordiazepoxide (0.3-10.0 mg/kg), oxazepam (0.3-3.0 mg/kg) and the benzodiazepine partial agonist, RU-32698 (3.0-17.0 mg/kg), led to increases in punished responding at intermediate doses and decreases at the highest doses tested. All benzodiazepine agonists brought about dose-dependent decreases in unpunished schedule-induced polydipsia, with doses required to reduce drinking proving higher than doses required to increase punished schedule-induced polydipsia. The antipunishment effect of 0.3 mg/kg of diazepam was dose-dependently antagonized by flumazenil and the benzodiazepine inverse agonist, RU-34000. Flumazenil effects, however, could reflect actions of flumazenil as a partial inverse agonist at GABAA receptors. RU-32698 at 10.0 mg/kg further facilitated the rate-increasing effect of 0.3 mg/kg of diazepam, but at 17.0 mg/kg partially blocked such antipunishment effect. Overall, the present results extend the similarities of the effects of benzodiazepine compounds on adjunctive and operant patterns of behaviour by showing similar interactions within the benzodiazepine receptor complex.

Cytochrome P450 (CYP) inhibition screening: Comparison of three tests

There are several different experimental systems for screening of in vitro inhibitory potency of drugs under development. In this study we compared three different types of cytochrome P450 (CYP) inhibition tests: the traditional single substrate assays, the fluorescent probe method with recombinant human CYPs, and a novel n-in-one technique. All major hepatic drug-metabolizing CYPs were included (1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4). Six compounds (sotalol, propranolol, citalopram, fluoxetine, oxazepam and diazepam) were selected for detailed comparisons. The IC50 values of each of these compounds were measured using the three assay types. The inhibitory potencies of these model drugs were generally within the same order of magnitude and followed similar inhibition profiles in all the assay types. Clinically observed inhibitory interactions, or lack thereof, were predictable with all three assays. Comparison of potencies of 'diagnostic' inhibitors revealed also some notable differences between the assays, especially regarding CYP2E1. The potency of inhibitors towards CYP3A4 was dependent on the substrate and reaction measured. Generally all three assays gave reasonably comparable results, although some unexplained differences were also noted.

Lateralization of the effects of the benzodiazepine drug oxazepam on medial olivocochlear system activity in humans

Benzodiazepines (Bzd) are known to interact with GABAergic inhibitory neurotransmission. Previous research on their effect on human auditory efferent pathways--through evoked otoacoustic emissions suppression by contralateral acoustic stimulation (CAS)--indicated a decrease in medial olivocochlear (MOC) efferent system inhibitory activity, after oral intake of oxazepam--representative of the Bzd drug class. To date, this pharmacological effect was only assessed in the right ear. Since a leftward asymmetry of Bzd receptors localization in human auditory cortex has been described recently, we explored in this study the hypothesis of an asymmetrical action of Bzd on MOC efferent functioning. The results revealed a significant difference of Bzd effect probing the right ear versus the left ear, with CAS-induced suppression being less effective in the right than left ear after oxazepam intake. This finding raises the question of possible neurochemical left-right asymmetry in the descending auditory pathways. The potential localization of this asymmetry is discussed.

Oxazepam does not modulate the behavioral effects of d-amphetamine in humans

Benzodiazepines, which are gamma-aminobutyric acid-A (GABA(A)) receptor positive modulators, can block the behavioral effects of psychomotor stimulants. In the present study, the ability of oxazepam, which may have less abuse potential compared to some other benzodiazepines, to attenuate the discriminative-stimulus, subject-rated and psychomotor performance effects of d-amphetamine in humans was determined. Six healthy participants (2 female, 4 male) learned to discriminate 15 mg oral d-amphetamine. After acquiring the discrimination (i.e., > or = 80% correct responding on 4 consecutive days), the effects of d-amphetamine (0, 2.5, 5, 10 and 15 mg), alone and in combination with acutely administered oxazepam (0 and 20 mg) were assessed. d-Amphetamine alone functioned as a discriminative stimulus, produced stimulant-like subject-rated effects (e.g., increased ratings of Stimulated on a Drug-Effect Questionnaire) and enhanced psychomotor performance. Oxazepam alone increased subject ratings of sedation (e.g., increased ratings of Sluggish, Fatigued and Lazy on a Drug-Effect Questionnaire) and impaired psychomotor performance. Oxazepam alone did not occasion d-amphetamine-like discriminative-stimulus effects, and had no effect on the discriminative-stimulus or subject-rated effects of d-amphetamine when given in combination. The results of this experiment are discordant with previous research and suggest that benzodiazepines differ in their ability to modulate the behavioral effects of d-amphetamine.

Unique patterns of gene expression changes in liver after treatment of mice for 2 weeks with different known carcinogens and non-carcinogens

Previously we demonstrated that the mouse liver tumor response to the non-genotoxic carcinogens oxazepam and Wyeth-14,643 involved more differences than similarities in changes in early gene expression. In this study we used quantitative real-time PCR and oligonucleotide microarray analysis to identify genes that were up- or down-regulated in mouse liver early after treatment with different known carcinogens, including oxazepam (125 and 2500 p.p.m.), o-nitrotoluene (1250 and 5000 p.p.m.) and methyleugenol (75 mg/kg/day), or the non-carcinogens p-nitrotoluene (5000 p.p.m.), eugenol (75 mg/kg/day) and acetaminophen (6000 p.p.m.). Starting at 6 weeks of age, mice were treated with the different compounds for 2 weeks in the diet, at which time the livers were collected. First, expression of 12 genes found previously to be altered in liver after 2 weeks treatment with oxazepam and/or Wyeth-14,643 was examined in livers from the various chemical treatment groups. These gene expression changes were confirmed for the livers from the oxazepam-treated mice in the present study, but were not good early markers for all the carcinogens in this study. In addition, expression of 20 842 genes was assessed by oligonucleotide microarray [n = 4 livers/group, 2 hybridizations/liver (with fluor reversals)] and the results were analyzed using the Rosetta Resolver System and GeneSpring software. The analyses revealed that several cancer-related genes, including Fhit, Wwox, Tsc-22 and Gadd45b, were induced or repressed in unique patterns for specific carcinogens and not altered by the non-carcinogens. The data indicate that even if the tumor response, including molecular alterations, is similar, such as for oxazepam and methyleugenol, early gene expression changes appear to be carcinogen specific and seem to involve apoptosis and cell cycle-related genes.

New Series of Morpholine and 1,4-Oxazepane Derivatives as Dopamine D4 Receptor Ligands: Synthesis and 3D-QSAR Model

Since the identification of the dopamine D(4) receptor subtype and speculations about its possible involvement in schizophrenia, much work has been put into development of selective D(4) ligands. These selective ligands may be effective antipsychotics without extrapyramidal side effects. This work describes the synthesis of a new series of 2,4-disubstituted morpholines and 2,4-disubstituted 1,4-oxazepanes with selectivity for the dopamine D(4) receptor. A 3D-QSAR analysis using the GRID/GOLPE methodology was performed with the purpose to get a better understanding of the relationship between chemical structure and biological activity. Inspection of the coefficient plots allowed us to identify that regions which are important for affinity are situated around the two benzene ring systems, a p-chlorobenzyl group, and the aliphatic amine belonging to the morpholine or 1,4-oxazepane system. In addition, the size of the morpholine or 1,4-oxazepane ring seems to be important for affinity.

Effects of oxazepam on methamphetamine-induced conditioned place preference

Our laboratory has been investigating the role for the hypothalamo-pituitary-adrenal (HPA) axis and benzodiazepines in the behavioral effects of cocaine for several years now. The following represents our initial investigation of the influence of benzodiazepines on methamphetamine reward using conditioned place preference. In these experiments, methamphetamine (0.5 mg/kg ip) resulted in a robust conditioned place preference that was attenuated when the rats were pretreated with oxazepam (10 mg/kg ip) on the day of preference testing. These data suggest a potential role for benzodiazepines in the behavioral effects of methamphetamine. Additional research will be necessary to determine if the nature of these effects is similar with what has been observed with cocaine.

UDP-Glucuronosyltransferase (UGT) 2B15 Pharmacogenetics: UGT2B15 D85Y Genotype and Gender Are Major Determinants of Oxazepam Glucuronidation by Human Liver

Oxazepam is a commonly used 1,4-benzodiazepine anxiolytic drug that is polymorphically metabolized in humans. However, the molecular basis for this phenomenon is currently unknown. We have previously shown that S-oxazepam glucuronide, the major oxazepam metabolite, is selectively formed by UDP-glucuronosyltransferase (UGT) 2B15, whereas the minor R-oxazepam glucuronide is produced by multiple UGTs other than UGT2B15. Phenotype-genotype studies were conducted using microsomes and DNA prepared from the same set of 54 human livers. Sequencing of the UGT2B15 gene revealed three nonsynonymous polymorphisms, D85Y, T352I, and K523T, with variant allele frequencies of 0.56, 0.02, and 0.40, respectively. D85Y genotype showed a significant effect (p = 0.012) on S-oxazepam glucuronidation with lower median activities in 85Y/Y livers (49 pmol/min/mg protein) compared with 85D/D livers (131 pmol/min/mg), whereas 85D/Y livers were intermediate in activity (65 pmol/min/mg). There was also a significant trend (p = 0.049) for higher S-oxazepam activities in the two 352T/I livers (135 and 210 pmol/min/mg) compared with the remaining 352T/T livers (median, 64 pmol/min/mg). Conversely, K523T genotype had no apparent effect on oxazepam glucuronidation (p > 0.05). Donor gender also significantly influenced S-oxazepam glucuronidation with higher median activities in male (65 pmol/min/mg) compared with female (39 pmol/min/ mg) livers (p = 0.042). R-Oxazepam glucuronidation was not affected by either genotype or gender (p > 0.05). In conclusion, gender and D85Y genotype are identified as major determinants of S-oxazepam glucuronidation by human liver and may explain in part polymorphic oxazepam glucuronidation by human subjects.

Effects of benzodiazepines on enzymes metabolizing drugs. IV. Effect of diazepam and oxazepam on hepatic microsomal drug metabolizing enzymes in rats exposed to high environmental temperature

Administration of diazepam or oxazepam caused a different response of the rat hepatic microsomal cytochrome P-450 dependent monooxygenase system. Both drugs produced significant decrease in the activity of NADH: cytochrome c oxidoreductase in rats exposed to 21 degrees C, but not to 28 degrees C and 35 degrees C, and did not change the activity of aniline hydroxylase, aminopyrine N-demethylase and 4-nitroanisole O-demethylase and cytochrome b5 level at any tested temperatures. Oxazepam, but not diazepam, caused a decrease in cytochrome P-450 content in rats exposed to 21 degrees C only. The results indicate that the high ambient temperature modifies the effect of tested benzodiazepines on the activity of some microsomal enzymes.

Influence of benzodiazepines on auditory perception

The aim of this study was to test for an influence of benzodiazepine (BZD) on various perceptual and/or cognitive auditory processes. Loudness, auditory selective attention, and the ability of subjects to form perceptual streams out of alternating tone sequences were tested. Nine subjects were tested before, 1, 3, 7, and 24 h after a single-dose oxazepam vs placebo administration in a crossover design. A sample of blood allows us to measure plasma oxazepam concentration. The results revealed a significant reduction in stream segregation expressed as d' scores 1 h after oxazepam intake in the test subjects. No significant change occurred across time in the same subjects when they were administrated a placebo in another session. Furthermore, oxazepam had no substantial and systematic influence either on auditory selective attention or on loudness perception. Altogether, these results suggest that the perceptual organization of sound sequences involves inhibitory neural mechanisms, which can be affected by BZDs. This outcome is consistent with existing models of auditory stream segregation and may be paralleled with earlier findings on the effect of BZDs on perceptual binding in the visual modality.

Effects of diazepam and its metabolites on nocturnal melatonin secretion in the rat pineal and Harderian glands. A comparative in vivo and in vitro study

We investigated the effects of diazepam (DZP) and its three metabolites: nordiazepam (NZP), oxazepam (OZP), and temazepam (TZP) on pineal gland nocturnal melatonin secretion. We looked at the effects of benzodiazepines on pineal gland melatonin secretion both in vitro (using organ perifusion) and in vivo in male Wistar rats sacrificed in the middle of the dark phase. We also examined the effects of these benzodiazepines on in vivo melatonin secretion in the Harderian glands. Neither DZP (10(-5)-10(-6)M) nor its metabolites (10(-4)-10(-5)M) affected melatonin secretion by perifused rat pineal glands in vitro. In contrast, a 10(-4)M suprapharmacological concentration of DZP increased melatonin secretion of perifused pineal glands by 70%. In vivo, a single acute subcutaneous administration of DZP (3 mg/kg body weight) significantly affected pineal melatonin synthesis and plasma melatonin levels, while administration of the metabolites under the same conditions did not. DZP reduced pineal melatonin content (-40%), N-acetyltransferase activity (-70%), and plasma melatonin levels (-40%), but had no affects on pineal hydroxyindole-O-methyltransferase activity. Neither DZP nor its metabolites affected Harderian gland melatonin content. Our results indicate that the in vivo inhibitory effect of DZP on melatonin synthesis is not due to the metabolism of DZP. The results also show that the control of melatonin production in the Harderian glands differ from that observed in the pineal gland.

Effects of lorazepam and oxazepam on perceptual and procedural memory functions

RATIONALE

Lorazepam has been found to consistently impair performance on both episodic and perceptual priming tasks, whereas other benzodiazepines have shown perceptual priming to be preserved. However, it has recently been postulated that benzodiazepines may exert time-dependent effects on implicit memory processes after research findings indicated some benzodiazepines, other than lorazepam, impair performance on priming tasks when tested at the time of peak plasma concentration level after benzodiazepine administration.

OBJECTIVES

To compare time-dependent effects of lorazepam and oxazepam on implicit memory tasks, specifically perceptual priming and procedural learning.

METHODS

Thirty-three healthy female undergraduates were randomised to one of three time groups (pre-peak, peak, post-peak) and administered placebo, 2.5 mg lorazepam, and 30 mg oxazepam, in counterbalanced order, at 1-week intervals. Assessments included word-stem completion (perceptual priming) and rotary pursuit (procedural learning) tasks.

RESULTS

At all time intervals, lorazepam but not oxazepam significantly impaired perceptual priming but procedural learning was preserved under both drugs.

CONCLUSIONS

These findings are consistent with previous research showing a differential effect of lorazepam in impairing perceptual memory but the notion that benzodiazepines exert time-dependent effects on implicit memory processes was not supported.

[An experimental study of tolerance to benzodiazepines]

The intention of the study was to demonstrate the appearance of the tolerance phenomenon after repeated administration of three of the most used benzodazepines (BDZ): Diazepam, Alprazolam and Oxazepam using three pharmacological tests, which monitored the neuromotor coordination, the myorelaxing and the anxiolitic effect. For each drug were used 3 doses, in geometrical progression, beginning with the partial dose, extrapolated from human to mouse according to the body surface. The treatment was made once a day, during 4 days. The appearance of tolerance was noticed, meaning an approximately 4-fold decrease of the sedative effect after the repeated administration of the 3 BDZ for all doses used. No tolerance was shown for the anxiolytic and myorelaxing effects, with the exception of alprazolam, which induced tolerance also for the myorelaxing effect. Our study has shown that repeated administration of BDZ might have different consequences on their pharmacological spectrum. The study indirectly explains the success of Alprazolam in therapy. This is due to the fact that small doses have approximately the some efficiency as the big ones in unique administration, decreasing the abuse potential. The rapid onset of the tolerance for the sedative and myorelaxing effect recommends its long-term administration in anxiolytic therapy.

Benzodiazepines have no effect on fear-potentiated startle in humans

RATIONALE

Pre-clinical and clinical investigations have provided a great deal of evidence that the fear-potentiated startle paradigm represents a valid model for the objective assessment of emotional states of anxiety and fear.

OBJECTIVE

The four studies presented in this report sought to further validate the "threat of shock" paradigm as a human analogue to fear-potentiated startle in rats, by examining the effect of benzodiazepine administration on both baseline and fear-potentiated startle.

METHODS

Three studies, conducted at Utrecht University, evaluated the effects of oxazepam and of diazepam on baseline and fear-potentiated startle, whereas a fourth study, conducted at Yale University, evaluated the effect of diazepam on baseline, contextual and cue-specific fear-potentiated startle. The threat of shock paradigm consisted of verbal instruction about two visual cues (the threat cue predicted the possible administration of electric shock, the other predicted a safe period), followed by a series of presentations of these cues. During these conditions, acoustic startle stimuli were presented in order to elicit startle responses. The magnitude of the startle response was used to index the degree of fear or alarm experienced during the periods of threat and safety. The fourth study examined the effect of IV administration of diazepam in a similar threat of shock paradigm except that there were two additional context manipulations: electrode placement and darkness.

RESULTS

None of the drug manipulations affected specific threat-cue potentiation of startle. However, reductions in baseline startle were observed. Further, startle potentiation by darkness was inhibited by diazepam.

CONCLUSIONS

At least one type of fear-potentiated startle, i.e. potentiation by a cue-specific fear manipulation, is not susceptible to benzodiazepine treatment. In contrast, effects of manipulations more akin to anxiety (darkness, context) appear sensitive to benzodiazepines. Human experimental models differentiating between these cue specific and contextual responses are needed to shed more light on differences in the anatomy and pharmacology of anxiety disorders.

Benzodiazepines differently modulate EAAT1/GLAST and EAAT2/GLT1 glutamate transporters expressed in CHO cells

It has been described recently that low concentrations of benzodiazepines stimulate the transport activity of the neuronal glutamate transporter EAAT3, whereas high concentrations inhibit it. The present study is aimed to investigate whether benzodiazepines have similar effects on the two glial glutamate transporter, EAAT1 and EAAT2. To this end, the transporters were transiently expressed in CHO cells and transport activity was determined by isotope fluxes using D-aspartate as non-metabolizable homologue of L-glutamate. At low D-aspartate concentrations (1 micromol/l) EAAT1-mediated uptake was reduced significantly by low concentrations of oxazepam (1 micromol/l) and diazepam (1 and 10 micromol/l). At 100 micromol/l D-aspartate oxazepam stimulated EAAT1-mediated uptake up to 150% in a dose dependent manner, whereas the inhibition by low concentrations of diazepam was attenuated. In contrast, a significant effect of diazepam on EAAT2-mediated uptake was only observed at 1000 micromol/l where uptake was inhibited by 60%. A similar inhibition was observed for EAAT1. These studies demonstrate a different modulation of EAAT1 and EAAT2 by benzodiazepines. Furthermore the glial transporters differ from the neuronal glutamate transporter. Thus, a complex in vivo response of the various transporters to benzodiazepines can be expected.

Pharmacological and endocrinological characterisation of stress-induced hyperthermia in singly housed mice using classical and candidate anxiolytics (LY314582, MPEP and NKP608)

The stress-induced hyperthermia test is a paradigm developed several years ago to model the expression of autonomic hyperactivity in anxiety. Whereas in the classical stress-induced hyperthermia, cohort removal was used, in a recently described modification of the stress-induced hyperthermia model singly housed mice rather than groups of mice were used. The modification of this model can be summarized as follows: rectal temperature is recorded in singly housed animals at two consecutive time-points (T1 and T2) which are interspaced by a defined time-interval (15 min). Since the value at the second temperature-recording exceeds the value of the initial measure it is the difference between these two core-temperatures which reflects stress-induced hyperthermia. In the present study, the stress-induced hyperthermia paradigm, in its modified design, was evaluated in OF1/IC mice. By comparing the effect of various compounds in both the modified as well as the classical (cohort removal) stress-induced hyperthermia paradigm, a very high correlation was found for the pharmacological sensitivity of the two paradigms. Furthermore, it was demonstrated that other anxiolytics, all known to be active in the classical stress-induced hyperthermia paradigm, such as the benzodiazepines chlordiazepoxide (0.3, 1, 3, 10 mg/kg, p.o.), diazepam (0.1, 0.3, 1, 3 mg/kg, p.o.), clobazam (5 or 10 mg/kg, p.o.) and oxazepam (5 or 10 mg/kg, p.o.) as well as the non-benzodiazepines buspirone (7.5 or 15 mg/kg, p.o.) and ethanol (15% or 30%, 10 ml/kg, p.o.), showed a marked reduction in stress-induced hyperthermia in the modified design. New candidate anxiolytics, i.e. the metabotropic glutamate (mGlu) receptor group 2 agonist LY314582 (1 or 10 mg/kg, p.o.; racemic mixture of LY354740 ((2S,4S)-2-amino-4-(4,4-diphenylbut-1-yl)-pentane-1,5-dioic acid), the metabotropic glutamate 5 receptor antagonist MPEP (1, 7.5, 15 or 30 mg/kg, p.o.; 2-methyl-6-(phenylethynyl)pyridine) and the neurokinin 1 (NK1) receptor antagonist NKP608 (0.01 or 0.1 mg/kg, p.o.; quinoline-4-carboxylic acid [trans-(2R,4S)-1-(3,5-bis-trifluoromethyl-benzoyl)-2-(4-chloro-benzyl)-piperidin-4-yl]-amide) also reduced stress-induced hyperthermia in the modified paradigm clearly indicating anxiolytic-like activity for these compounds. Finally, the effects of the classical benzodiazepine chlordiazepoxide (10 mg/kg, p.o.), in parallel with its effect on stress-induced hyperthermia, were also investigated for its effect on plasma concentrations of the two stress hormones, adrenocorticotropin (ACTH) and corticosterone. It was shown that all three parameters were significantly increased 15 min after T1 in vehicle-treated mice whereas the increase was significantly attenuated following pre-treatment with chlordiazepoxide. In conclusion, all the data presented here indicate that the modified version of the stress-induced hyperthermia-paradigm is a valid and interesting alternative to the classical stress-induced hyperthermia test.

Comparison of the mutant frequencies and mutation spectra of three non-genotoxic carcinogens, oxazepam, phenobarbital, and Wyeth 14,643, at the lambdacII locus in Big Blue transgenic mice

Oxazepam (OX), a widely used benzodiazepine anxiolytic, phenobarbital (PHE), a drug used for convulsive disorders, and Wyeth 14,643 (WY; [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid), a hypolipidemic agent, are all hepatocarcinogenic in B6C3F1 mice. They have been classified as "non-genotoxic" carcinogens since they are non-DNA reactive in in vitro assays and are either negative or weakly positive in Salmonella typhimurium (Ames assay). Male B6C3F1 Big Blue(R) transgenic mice were fed 2500 ppm of OX or PHE or 500 ppm of WY in their diet, while a control group of mice received diet alone for 180 days. The mutant frequency (MF) of cII in the control mice, after correction for clonality, was 6.2 +/- 2.8 x 10(-5). The MF values for mice fed OX, PHE, and WY were 10.0 +/- 3.6 x 10(-5) (P < 0.05), 7.9 +/- 1.3 x 10(-5) (P = 0.1) and 17.4 +/- 4.2 x 10(-5) (P < 0.01), respectively. The mutation spectrum (MS) at cII from the PHE-fed mice was significantly different (P < 0.05) from that of the control mice even though the MF was not, whereas the MS spectra of mice fed OX (P = 0.4) and WY (P = 0.7) were not significantly different. The PHE-derived spectrum differed from the spontaneous spectrum in the lower occurrence of G:C>C:G transversions (17 vs 1.6%) and the higher incidence of A:T>T:A transversions (3.4 vs 9.5%). Prior to correction for clonal expansion, each treated group exhibited a high incidence of frameshift mutations at the homopolymeric run of guanines at bp 179-184 (OX 21%, PHE 21%, WY 16% of the total mutations); this was not the case with the control group (6%). Even after clonal correction, more than 10% of the mutations were frameshifts in the treated mice, while 5% were frameshifts in the control mice. Despite this hypersensitive region of the gene, our findings suggest that the cII locus is less sensitive than the lacI locus to mutation induction by non-DNA reactive carcinogens.

Oxazepam alters action monitoring

RATIONALE

Oxazepam has been demonstrated to slow reaction times and increase the rate of omission errors in attentional experiments. This suggests that action monitoring might also be impaired.

OBJECTIVES

The present study used the event-related brain potential (ERP) technique to investigate this hypothesis. The P3b component to targets was taken as an indicator of the target evaluation process, and the response-locked error-related negativity (ERN) served as an indicator of action monitoring. We hypothesized that the amplitudes of ERN and P3b would be reduced as an effect of oxazepam.

METHODS

A simple "oddball" reaction time experiment was conducted in a double-blind crossover study of 30 mg oxazepam versus placebo. In order to investigate variations in attentional allocation, separate experimental runs were undertaken with target frequencies of 50% and 80%.

RESULTS

ERN and P3b amplitudes were lower in the 80% target condition than in the 50% condition. Oxazepam did not affect behavioral parameters but was associated with an ERN of lower amplitude than the placebo condition. ERN amplitude variations between target conditions remained unchanged.

CONCLUSIONS

Although the intake of 30 mg oxazepam did not impair behavioral performance, measures of the electrophysiological recordings show that action monitoring processes were altered. We argue that this may be related to the anxiolytic properties of the drug and may constitute an important causal factor for behavioral impairments after the intake of oxazepam.

[Dose-dependent tazepam modulation of amplitude-temporal characteristics of thalamocortical responses and the constant potential of the sensorimotor cortex in rabbits at eye opening]

The pronounced benzodiazepine (antiphobic) modulation of the amplitude-temporal parameters of different components of the thalamocortical responses (TCR) of the sensorimotor cortex is observed in rabbits in their early postnatal ontogeny. This modulation is of a dose-dependent character and is registered not after the injection of tazepam in a concentration of the "therapeutic tranquilizing window" but also in the psychotoxic plasma range. A gradual increase in blood tazepam concentration in a young rabbit pup is accompanied by the wave-like and differential decrease in the amplitude of the second and third positive (P2 and P3) and third negative (N3) TCR components, while the second negative (N2) and fourth positive (P4) components tend to a wave-like increase. The dose-dependent dynamics of tazepam modulation of the P2, P3, and N3 latencies is characterized by a wave-like and differential increase. The latency of P4 decreases slightly and that of the N2 increases with a low degree of significance. The selective dynamics of benzodiazepine modulation appears to be related with peculiarities of the electrogenesis of each of the components. The dose-dependent modulation of the level of cortical DC potential is of the same character as the respective amplitude changes in P2, P3, and N3, but its fluctiatuons are more pronounced.

Effect of benzodiazepines on the epithelial and neuronal high-affinity glutamate transporter EAAC1

EAAC1-mediated glutamate transport concentrates glutamate across plasma membranes of brain neurons and epithelia. In brain, EAAC1 provides a presynaptic uptake mechanism to terminate the excitatory action of released glutamate and to keep its extracellular concentration below toxic levels. Here we report the effect of well known anxiolytic compounds, benzodiazepines, on glutamate transport in EAAC1-stably transfected Chinese hamster ovary (CHO) cells and in EAAC1-expressing Xenopus laevis oocytes. Functional properties of EAAC1 agreed well with already reported characteristics of the neuronal high-affinity glutamate transporter (Km D-Asp,CHO cells: 2.23+/-0.15 microM; Km D-Asp,oocytes: 17.01+/-3.42 microM). In both expression systems, low drug concentrations (10-100 microM) activated substrate uptake (up to 200% of control), whereas concentrations in the millimolar range inhibited (up to 50%). Furthermore, the activation was more pronounced at low substrate concentrations (1 microM), and the inhibition was attenuated. The activity of other sodium cotransporters such as the sodium/D-glucose cotransporter SGLT1, stably transfected in CHO cells, was not affected by benzodiazepines. In electrophysiological studies, these drugs also failed to change the membrane potential of EAAC1-expressing Xenopus laevis oocytes. These results suggest a direct action on the glutamate transporter itself without modifying the general driving forces. Thus, in vivo low concentrations of benzodiazepines may reduce synaptic glutamate concentrations by increased uptake, providing an additional mechanism to modulate neuronal excitability.

Effects of oxazepam and acetaminophen on cicletanine metabolism in rat hepatocytes and liver microsomes

Cicletanine, a racemic furopyridine derivative synthesized as racemate, is used as an antihypertensive agent. Its two enantiomers are involved in the pharmacological effects of the drug. Cicletanine is metabolized by conjugation enzyme systems (phase II) into sulfoconjugated or glucuroconjugated enantiomers. As oxazepam and acetaminophen are widely prescribed, especially to elderly patients, these two drugs may be co-administered with cicletanine. The metabolic profile and the kinetics of biotransformation were studied by using rat hepatocytes and liver microsomes. Cicletanine was extensively metabolized by rat hepatocytes. More than 80% of the drug was biotransformed after a 3 h incubation. The formation of glucuroconjugated metabolites was characterized by the following kinetic parameters, i.e. Vmax = 2.05 +/- 0.21 nmol/min/mg protein and Km = 287 +/- 6.7 microM for (-)-cicletanine, and Vmax = 1.44 +/- 0.12 nmol/min/mg protein and K(m) = 171 +/- 4.1 microM for (+)-cicletanine. Oxazepam inhibited the glucuronidation of cicletanine in both rat hepatocytes and liver microsomes with a competitive-type inhibition, i.e. K(i) = 129 +/- 7.5 and 152 +/- 19.7 microM for (-)-cicletanine and (+)-cicletanine, respectively. The co-incubation of acetaminophen with cicletanine showed that only sulfoconjugation was inhibited in rat hepatocytes. Glucuronidation was not modified by acetaminophen. As natriuric activity is due to sulfoconjugated (+)-cicletanine, acetaminophen could potentially modulate in vivo the pharmacological effect of cicletanine. The data of the in vitro study reported here suggested an interaction between cicletanine and oxazepam or cicletanine and acetaminophen. However, the clinical impact of such a drug interaction needs further evaluation.

Single dose pharmacokinetics and pharmacodynamics of oxazepam in normal and renal dysfunction rats

The purpose of this work was to investigate the disposition characteristics and pharmacodynamics of a benzodiazepine, oxazepam, in renal dysfunction rats. For the in vivo experiment, normal and renal dysfunction rats were given 40 mg/kg of oxazepam as the bolus dose. A quantitative electroencephalographic (EEG) method was used as the surrogate measure of the pharmacological response. The oxazepam concentration in plasma and cerebrospinal fluid (CSF) was assayed by the HPLC method. The steady-state volume of distribution and clearance based on total and unbound plasma did not change in renal dysfunction rats. Amplitude changes in the EEG induced by oxazepam in normal and renal dysfunction rats were characterized by a log-concentration response model or sigmoidal Emax model. The pharmacodynamic parameters from these models were not altered in renal dysfunction. In in vitro binding studies for gamma-aminobutyric acid (GABA)-benzodiazepine receptor complex, the oxazepam-induced effect was not potentiated by the plasma dialysate from renal dysfunction rats. Thus, it was suggested that the brain sensitivity to benzodiazepines was not altered in renal insufficiency.

An examination of differences in the time course of oxazepam's effects on implicit vs explicit memory

The present study was designed to examine the effects of oxazepam on implicit vs explicit memory processes, as a function of this drug's time course. The effects of oxazepam (30 mg) or placebo on directly comparable tests of implicit memory (word stem completion) and explicit memory (cued recall) were examined at three time points: 100 min post-drug administration (prior to the theoretical peak plasma concentration of oxazepam; i.e.'pre-peak' condition), 170 min post-drug (close to theoretical peak; i.e. 'peak' condition) or 240 min post-drug (following theoretical peak: i.e. 'post-peak' condition). Sixty healthy volunteers were randomly assigned to either the drug condition or the placebo condition in a double-blind design and were tested on both memory tests at one of the three time points. In the 'pre-peak' condition, oxazepam impaired cued recall performance relative to placebo but did not impair priming. In the 'peak' condition, oxazepam impaired performance on both memory tasks. In the 'post-peak' condition, cued recall performance in the oxazepam group remained significantly impaired relative to placebo. However, oxazepam-induced impairments in priming were only marginal, suggesting that oxazepam-induced impairments in implicit memory processes begin to wane following theoretical peak drug concentrations. The fact that oxazepam-induced priming impairments were significant only when the word stem completion task was administered close to peak plasma concentrations, supports the hypothesis that benzodiazepines exert time-dependent effects on implicit memory processes. The results also support the theoretical distinction between implicit and explicit memory processes, since the directly comparable implicit and explicit tasks showed different impairment curves over time.

Plasma and CSF benzodiazepine receptor ligand concentrations in cirrhotic patients with hepatic encephalopathy: relationship to severity of encephalopathy and to pharmaceutical benzodiazepine intake

Increased plasma and CSF concentrations of substances which bind to brain benzodiazepine receptors have previously been reported in cirrhotic patients with hepatic encephalopathy (HE). However, their relationship to previous intake of pharmaceutical benzodiazepines has not been clearly established. In the present study, plasma levels of benzodiazepine receptor ligands (BZRLs) were measured using a sensitive radioreceptor assay in 12 control subjects with no evidence of hepatic, neurological or psychiatric illness, 11 cirrhotic patients without HE, 24 cirrhotic patients with moderate (grade I-II) HE and in 45 cirrhotic patients with severe (grade II-IV) HE. In addition, CSF concentrations of BZRLs were measured in 8 cirrhotic patients with HE and an equal number of age-matched controls. Recent intake (within 10 days) of pharmaceutical benzodiazepines was assessed by detailed review of medical files, and interviews with the patient, at least one family member as well as the pharmacist. Significantly increased plasma concentrations of BZRLs were observed in cirrhotic patients with severe encephalopathy (p < 0.02) compared to controls and to cirrhotic patients without (or with mild) neurological impairment. Increased plasma BZRLs could be accounted for by prior exposure to benzodiazepine medication in all cases. CSF concentrations of BZRLs in cirrhotic patients were not significantly different from control values. These findings do not support a role for "endogenous" benzodiazepines in the pathogenesis of HE in chronic liver disease but suggest that pharmaceutic benzodiazepines administered to cirrhotic patients as sedatives or as part of endoscopic work-up could have contributed to the neurological impairment in some patients.

A further examination of the time-dependent effects of oxazepam and lorazepam on implicit and explicit memory

Until recently, research indicated that all benzodiazepines impair explicit memory, while only lorazepam impairs priming. Stewart and associates provided preliminary data which indicated that both oxazepam and lorazepam may impair implicit memory, but in a time-dependent fashion. The present study was designed to replicate Stewart et al.'s findings after overcoming several limitations of the original study. Thirty subjects were administered an acute dose of lorazepam (2 mg), oxazepam (30 mg) or a placebo and were tested with an implicit (word-stem completion) test and an explicit (cued recall) test. However, subjects were only tested at 170 min post-drug (close to oxazepam's theoretical peak concentration) to rule out the possible "explicit memory contamination" explanation of the Stewart et al. implicit memory findings. Consistent with previous research, both drugs impaired explicit memory relative to placebo. Also, both lorazepam and oxazepam impaired priming performance, supporting the "time-dependence" interpretation of the Stewart et al. findings. The results also indicate that episodic memory is impaired by both benzodiazepines in a time-dependent fashion even when the research methodology used involves everyday memory demands.

Benzodiazepines alter cochleo-cochlear loop in humans

By using otoacoustic emission, we looked for change in outer hair cell (OHC) motile activity and medial olivocochlear (MOC) system inhibition due to benzodiazepine administration, a drug that is known to produce a pharmacological effect by interacting with GABAergic inhibitory neurotransmission. No effect was observed on OHC motile activity, in contrast benzodiazepines decreased MOC system effectiveness suggesting the existence of GABAergic fibers projecting onto the MOC system.

An anxiolytic-like effect of ondansetron disappears in oxazepam-tolerant rats

In our experiments a drug from the group of 5-HT3 antagonists--ondansetron (OND)--has been used in rats developing tolerance to oxazepam (OXZ). After 7 days of oxazepam administration (5 mg/kg i.p.) a significant decrease in the anxiolytic behavior was observed in the Crawley test. In the rats already partly tolerant to oxazepam, an undiminished anxiolytic-like effect of ondansetron (single injection of 0.1 mg/kg i.p., seventh day) was observed. After 14 days of oxazepam administration its anxiolytic activity was even more diminished. A single injection of ondansetron 0.1 mg/kg restored the anxiolytic behavior: rise of BWT (black-white transition) and WSE (white square entrance). After 21 days the anxiolytic activity of oxazepam was totally abolished and the single injection of ondansetron did not restore the state of anxiolysis. The results show that the anxiolytic effects of ondansetron were not influenced in the first stages of tolerance development to oxazepam, but the drug was not able to produce an anxiolytic effect in the state of full tolerance to oxazepam (after 3 weeks).

The effect of chronic benzodiazepines exposure on body weight in rats

Changes in body weight (BW) in female rats treated for 5 weeks (wk) with weekly subcutaneous implantation of silastic capsules containing different benzodiazepines (BZs): diazepam (DZ) 90, 180, 360 and 540 mg wk-1; nordiazepam (ND) 600 mg wk-1; oxazepam (OX) 600 mg wk-1 and flunitrazepam (FN) 540 mg wk-1 and in male rats exposed to DZ (540 mg wk-1) were evaluated herein. Rats (female and male) implanted with empty capsules served as controls. The BW gain was significantly higher in male than in female rats (both DZ-treated and controls). The BW gain increased with increasing doses of DZ but slowed with time of exposure. In comparison to control rats, the BW gain was significantly higher in DZ-(540 mg wk-1) and OX- but not in ND- and FN-treated female rats. However, the differences between BZs were not of statistical significance. In rats exposed to empty capsules (male, female); DZ (male); ND and OX (female) the BW gain increased with time (1-4 wk) while in rats exposed to DZ and FN (female) the BW stabilised within 2 wk. Acute injection of the central BZ receptor antagonist, flumazenil (40 mg kg-1, i.v., 5th wk of chronic exposure), tended to inhibit the time-related BW gain in rats exposed to empty capsules (male, female), DZ (male), ND and OX (female) but did not affect the BW in DZ- (540 mg wk-1) and FN-exposed rats (female) where BW stabilised prior to FLU injection. Repeated administration of flumazenil (30 mg kg-1 wk-1, i.p.) did not affect the BW gain in DZ- and ND-treated female rats. The present data indicate that different BZs have different effects on BW gain in the rat suggesting that different subtypes of BZ receptors are involved.

Effects of alcohol and hypnosedative drugs on digit-symbol substitution: comparison of two different computerized tests

Computerized symbol-digit substitution tests (SDSTs) and 'yes/no' digit-symbol substitution tests (YNDSTs), together with a digit-digit copying test (DDCT) were compared in a double-blind crossover study for hypnosedative and alcohol effects in 12 young healthy subjects. The tests were carried out before and 1, 3.5 and 5 h after intake of 15 mg diazepam, 30 mg oxazepam, 7.5 mg zopiclone, 15 mg zolpidem or 0.65+0.35 g/kg ethanol, these impaired performance by varying extents. The drug-induced decrements were similar in the YNDSTs and SDSTs; the errors were subject-related and increased with alcohol intake in the YNDSTs but not in the SDSTs. Pooled baseline values in YNDSTs correlated well (Pearson) with those in the SDSTs. The SDSTs also correlated well with the DDCTs. The same correlations were seen when comparing absolute performances after ethanol and hypnosedatives. When using the delta-values (changes from baseline), the correlation between YNDSTs and SDSTs was high after placebo but low after alcohol and hypnosedatives. When using ANCOVA to measure the responses to drugs (delta-drug-delta-placebo), the correlation between YNDSTs and SDSTs was fairly significant after most but not all active drugs. Subjective visual analogue variables did not correlate with objective performances. By comparing absolute performances with hypnosedatives we conclude that YNDSTs and SDSTs are similar, with the delta-values indicating differences between them.

On mouse pups and their lactating dams: behavioral consequences of early exposure to oxazepam and interacting factors

Behavioral analysis in animal models appears to be a valuable and sensitive tool for detecting subtle alterations in CNS function, which can be produced by early exposure to small perturbations of sensory experience, hormonal milieu, or exposure to psychotropic agents devoid of major teratogenic potential. Concerning anxiolytics, the more recent work in mice, which is here summarized, was carried out by putting the emphasis on changes in naturally occurring species-typical social responses as a function of early exposure to benzodiazepines. For adult females, on the behavior expressed during the early postpartum period, whereas for infant subjects, on the ontogenetic stage of the establishment of social bonding. Critical issues such as the choice of fostering procedure and rearing conditions are also addressed. Evidences of relationships between changes in social milieu taking place during early rearing-i.e., when dramatic transitions in the neurochemical target system occur- and the adult behavioral response to challenges with BDZ agents are presented. These data strengthen the notion that the modes of reaction of adult animals to the joint influence of physiological and environmental (stimulus) variables are under the influence of events in early ontogenesis. Therefore, a better understanding of the mechanisms-as unveiled by an appropriate use of drug tools-that mediate such a plasticity might have considerable psychobiological and clinical-therapeutical relevance.

Effects of oxazepam and lorazepam on implicit and explicit memory: evidence for possible influences of time course

The effects of oxazepam (30 mg), lorazepam (2 mg), and placebo on implicit and explicit memory were studied in two testing cycles, 100 and 170 min after drug administration. Thirty healthy volunteers were randomly assigned to one of three groups (placebo, oxazepam, or lorazepam) in a double-blind, independent groups design. Drug groups were equivalent prior to drug administration on a variety of cognitive measures. Following drug administration, both oxazepam and lorazepam equally impaired performance on a cued-recall explicit memory task relative to placebo, at both testing cycles. Relative to placebo, lorazepam markedly impaired priming on a word-stem completion implicit memory task, at both testing cycles. Consistent with previous work, oxazepam failed to produce impairments in priming on the word-stem completion task at 100 min post-drug administration. However, oxazepam was found significantly to impair priming on this latter task relative to placebo, at close to theoretical peak plasma concentration (i.e., 170 min post-drug administration). Explanations for the observed detrimental effect of oxazepam on implicit memory task performance are considered, including: possible time-dependent effects related to the relative rate of absorption of these two benzodiazepines (BZs); and potential contamination of the implicit memory task by explicit memory strategies during the second testing cycle.

Fear-potentiated startle response is remarkably similar in two laboratories

The fear-potentiated startle response paradigm is used to investigate anxiolytic properties of drugs. The first objective of the present study was to further investigate the predictive validity of this paradigm. The anxiolytics chlordiazepoxide (2.5-10 mg/ kg IP) and oxazepam (1-10 mg/kg PO) and the putative anxiolytic flesinoxan (1-10 mg/kg PO) decreased startle potentiation dose-dependently, indicating an anxiolytic effect. The antidepressant fluvoxamine (5-20 mg/kg PO) did not affect startle potentiation. Ideally, anxiolytic drugs attenuate startle potentiation without affecting control startle levels, although some studies report altered control startle amplitudes. The second objective was to investigate whether different effects on control startle amplitudes are related to different startle devices. Therefore, the drugs were tested in two laboratories. Results showed no significant differences between laboratories, indicating that equipment is not a critical factor in the drug-induced alteration of control startle levels. In an additional experiment, it was shown that flesinoxan (10 mg/kg PO) did not affect strychnine-induced startle potentiation, supporting the idea that the attenuating effect of flesinoxan on the fear-potentiated startle response is due to its anxiolytic properties. Thus, the fear-potentiated startle response paradigm appears a valid and reliable model for anxiolytic properties of drugs.

Effects of oxazepam on event-related brain potentials, EEG frequency bands, and vigilance performance

Eighteen males performed two vigilance tasks with static and dynamic stimuli under the influence of oxazepam (20 and 40 mg) in a placebo-controlled, double blind, crossover design. Oxazepam dose-dependently impaired overall level of performance and aggravated the decrement with time in measures of accuracy and sensitivity relative to placebo. The drug reduced the amplitudes of the P1, N1, P2N2, and P3 (dose-dependently) waves of event-related potentials (ERPs). Oxazepam aggravated the linear decline with time of the P3 amplitude only. Oxazepam impaired accuracy was related to deterioration of central processing involved in stimulus discrimination (P2N2). Impairment of response-related performance measures (RT and RI) was associated with processing manifest in the P1, N1, and P3 waves. Oxazepam effects on the amplitudes of N1 and P3 correlated with drug effects on power in alpha 1 (8-10 Hz). Drug effects on overall performance and alpha were also related; the drug effect on response speed correlated only with the drug effect on beta 1 (12.5-21 Hz). Effects of time-on-task on performance and EEG were unrelated, but oxazepam induced performance declines with time may have been caused by declines in resource allocation, as manifest in the amplitude of P3. Time effects on EEG power bands and ERP amplitudes were not significantly related to the time course of oxazepam activity. A curious dissociation emerged: both oxazepam and time-on-task impaired performance, but the drug induced a decrease of theta and alpha 1 power, whereas time-on-task increased power. Various processes play a role in performance decrements with time, and various aspects of processing may be involved in signal-detection measures which makes terms such as sensitivity quite meaningless. So-called computational processing was indistinguishable from energetic processes, which questions the validity of the distinction between these two domains. Explanations of EEG activity in terms of a unidimensional theory of arousal are untenable.

Flumazenil, diazepam, nordiazepam and oxazepam interactions on plasma protein binding

The effect of flumazenil (FLU) on plasma protein binding of diazepam (DZ), nordiazepam (ND) and oxazepam (OX) was determined in plasma from drug-naive dogs to which graded concentrations of tested drugs alone and in combination were added. The results revealed that as the concentration of FLU added to plasma alone was increased its binding with plasma proteins decreased and that there were no significant binding interactions between FLU and OX, ND and DZ.

Limited changes of mouse maternal care after prenatal oxazepam: dissociation from pup-related stimulus perception

There is evidence that activity at the GABA/benzodiazepine receptor complex in specific brain areas might be enhanced during rodent motherhood. We tested the hypothesis that the manipulation of this neurochemical system by prenatal benzodiazepine exposure affects typical behavioral responses of lactating mouse dams. Outbred CD-1 mouse fetuses were administered either oxazepam (OX, 15 mg/kg) or vehicle twice a day on embryonic days 12-16 and fostered at birth to untreated dams. Female offspring were subsequently mated at the young adult stage. In a first experiment, the behavioural repertoire of the two groups of lactating females was scored (single 10-min session) from postpartum days 3 to 18. When compared with VEH dams, OX females showed a shorter duration of pup-sniffing at 7-10 days and enhanced crouching behaviour when pups had reached the age of 14-18 days. In addition, OX-treated dams used more cotton for nest construction than the controls. The two female groups were differentiated only in the presence of their offspring. In a second experiment aimed at investigating possible OX-induced changes in pup-stimulus perception, the same lactating females were challenged in sequence on postpartum day 8 with three different patterns of pup-related cues consisting of: three 8-day-old live male pups (LP), three same-age dead pups DP, or three dead pups accompanied by pre-recorded ultrasounds (DPU). In the absence of carry-over effects of prenatal dam treatment, LP stimuli elicited a higher frequency of sniffing and digging than the others, whereas the level of licking, and grooming was reduced. In conclusion, the present results indicate that the slight alteration in maternal care resulting from prenatal OX treatment can be dissociated from changes in pup-related stimulus perception.

A comparison of behavioural effects of prenatally administered oxazepam in mice exposed to open-fields in the laboratory and the real world

Prenatal benzodiazepine exposure has been reported to result in abnormal neurobehavioural development in laboratory animals but little is known about the behavioural relevance of this effect ina naturalistic environment. In this study, outbred CD-1 male mice were prenatally exposed to oxazepam (15 mg/kg per os, twice daily) on days 12-16 of fetal life and fostered at birth to untreated dams. At adulthood, each mouse was fitted with a radio collar and its first reactions assessed. Three hours later, behavioural and exploratory activities were recorded in a laboratory open field, and 24 h later in a natural setting. Immediate reactions to the radio collar were higher in the oxazepam-treated mice than in controls consisting of more attempts to remove it and an increase of push-digging. The attempts to remove the collar were still evident in oxazepam treated mice tested in the laboratory open-field 3 h later. Moreover, oxazepam increased the frequency of grooming and reduced walking in both the laboratory and the natural settings. In the natural settings running was increased during the initial 30-min test, while a pronounced level of grooming and a lower frequency of eating were observed 140 min after release. Frequency of sniffing, grooming, and rearing behaviours were higher in the laboratory test when compared to the natural settings. On the other hand, prolonged bouts of sniffing were recorded in the natural environment. These findings permit separation of robust drug effects (increased grooming, reduced walking) from situation-dependent effects, the natural environment revealing, in addition, more subtle effects.

Pupillometric assessment of compensatory effort in a memory search task under physical and pharmacologically-induced suboptimal states

Extensive research has shown that the phasic pupil size (peak level on each trial) is a sensitive measure of the degree of mental effort demanded by a task. In the present study, the validity of the pupil response as an index of mental effort in suboptimal conditions was investigated. Thirteen males (19-29 years) performed a memory and display-search task in a practice session, followed in random order by an oxazepam session, a placebo session, a physical exercise session, and a control session. After both oxazepam and physical exercise, decision times increased, but pupil response increased only after physical exercise. This result was explained by the possibility that under physical fatigue, compensatory effort was exerted, whereas under drug-induced fatigue, subjects seemed unable to compensate for the performance decrement. The pupil response appears to be a valuable tool for gaining more insight into different effects of suboptimal states.

Precipitated withdrawal in squirrel monkeys after repeated daily oral administration of alprazolam, diazepam, flunitrazepam or oxazepam

The lowest dose of alprazolam, diazepam, flunitrazepam and oxazepam consistently to induce loss of righting reflex in squirrel monkeys or vehicle was orally administered to monkeys on 18 consecutive days: 2 mg/kg alprazolam (n = 4), 30 mg/kg diazepam (n = 4), 1 mg/kg flunitrazepam (n = 4), 280 mg/kg oxazepam (n = 5), or vehicle (n = 4). Tolerance developed rapidly for loss of righting reflex, more slowly for sleep and only minimally for muscle relaxation observed during the period immediately following daily oral administration. Injection of the specific benzodiazepine receptor antagonist flumazenil (10 mg/kg i.v.) 5 h after the ninth daily oral treatment produced signs of precipitated withdrawal (tremor, vomiting and/or convulsions) in one alprazolam-, four diazepam-, one flunitrazepam- and four oxazepam-treated monkeys, but not in the vehicle-treated monkeys. Physiological saline injected intravenously several days later under these same experimental conditions failed to provoke a precipitated withdrawal reaction. When flumazenil-induced precipitated withdrawal was again evaluated after the 18th daily oral treatment, withdrawal signs were observed in all alprazolam- and all diazepam-treated monkeys, as well as in three flunitrazepam- and three oxazepam-treated monkeys, but not in the vehicle-treated monkeys (convulsions were observed in one alprazolam-, two diazepam-, one flunitrazepam- and two oxazepam-treated monkeys). No signs of spontaneous withdrawal were observed in any of the monkeys during a subsequent 3-week drug-free period. Thus, repeated administration of approximately equieffective doses of these four benzodiazepines resulted in a similar development of tolerance and physical dependence (indicated by the occurrence of a precipitated withdrawal reaction).

Metabolism and elimination of oxazepam in F344 rats

The antianxiety agent, oxazepam, is a mouse liver carcinogen as determined by a National Toxicology Program bioassay. An equivalent study in the F344 rat is currently in progress. In an effort to gain insight into whether the mouse or rat will be a better model for human risk assessment, extensive comparative metabolism studies have been conducted in both rodent species and compared with the human literature. In this study, male rats were treated with 25, 250, or 500 mg/kg of radiolabeled oxazepam. In addition, sex comparisons were made at 500 mg/kg after 0 and 14 days of 2500 ppm oxazepam in the feed to mimic bioassay conditions. Similar studies have already been conducted in mice. Recovery of administered activity was dose-dependent, with recovery approaching 100% at the low dose. In all groups, the order of importance of route of elimination was fecal > urinary > expired. No significant sex-dependent differences were detected. Oxidative metabolism and sulfate conjugation were the major routes of metabolism. Pretreatment of animals with oxazepam-dosed feed resulted in evidence of hepatic enzyme induction. The rate of elimination for all three routes of elimination was elevated by dosed feed treatment. With regard to metabolite profile and routes of elimination, the rat is less like a human than the mouse.

Induction of maternal behavior by mouse neonates: influence of dam parity and prenatal oxazepam exposure

The aim of the present report was to investigate the influence of pup stimulus properties and female parity on mouse maternal behavior. Outbred CD-1 mouse pups, prenatally exposed to either the vehicle (VEH) or oxazepam (OX, 15 mg/kg twice/day on pregnancy days 12-16) and fostered to untreated dams at birth, were offered as a stimulus on postnatal days 4, 6, and 8 to four groups of females that differed in maternal experience: virgin, experienced virgin females, primiparae, and biparae. Maternal behavior was observed during a 15-min session each day. Virgin females were less involved in crouching behavior than primiparae. Pups, age, and prenatal oxazepam showed interactive effects on maternal care, particularly by increasing licking and nest-building activities and decreasing still-out behavior. Moreover, dams receiving younger pups showed high levels of both locomotor activity and rearing. The present findings point to the need for a better understanding of mother-pup interactions in studies aimed at characterizing drug and toxicant effects on both animal and human development.

Effects of oxazepam on performance and event-related brain potentials in vigilance tasks with static and dynamic stimuli

Eighteen males performed two vigilance tasks with static and dynamic stimuli under the influence of oxazepam (20 and 40 mg) in a placebo-controlled, double blind, crossover design. Oxazepam (40 mg) caused impaired performance in the early part of a task with stimuli inducing frequent saccadic eye movements (dynamic task), relative to a task in which the stimuli remained at the same location (static task). This could not be explained by effects of the drug on oculomotor behavior. A larger diameter of the pupil in the dynamic task indicated that performance on this task may have required more effort. Stimulus processing requirements were higher in the dynamic task, as suggested by event-related brain potentials (ERPs), in particular the P3 wave; i.e., more resources had to be allocated in this task. This (additional) investment of resources appeared impossible after administration of oxazepam (40 mg). The conclusion was that tasks eliciting frequent eye movements require more effort and processing resources.

Pharmacopsychological effects of oxazepam and kava-extract in a visual search paradigm assessed with event-related potentials

The effects of oxazepam and a standardized extract of kava-roots (WS1490, W. Schwabe, Karlsruhe) on reaction time and event-related potentials (ERPs) were investigated in a visual search paradigm using a double-blind design in young, healthy males. Significant effects of oxazepam were obtained in a number of psychometric tests as well as search time and quality. Several ERP components of different latency, topography and functional significance were affected by the medications. Oxazepam led to a reduction of the amplitude of the parietal N1, frontal N2, posterior contralateral N2, and occipital P3 components. WS 1490 was associated with a greater posterior N1, posterior contralateral N2, and occipital P3. The effects are discussed in the light of the functional properties of the components and provide clues as to the psychological site of action of the drugs.

Central effects of the diuretic, bendrofluazide

1. Central effects of the diuretic, bendrofluazide (2.5, 5 and 10 mg) were studied in 12 healthy volunteers. Two placebos and an active control drug, oxazepam (15 mg), were included. Single doses were administered double-blind at 10.00 h. The effects of drugs on performance and subjective feelings were assessed before and from 1.5-2.5 and 3.5-4.5 h after ingestion, and recording of the electrical activity of the brain (EEG) and body sway carried out. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. The EEG was recorded with eyes open while the subjects carried out a mental arithmetic task, and with eyes closed, when they were required to relax. Body sway was recorded with eyes open and with eyes closed. 3. Bendrofluazide (10 mg) increased the number of errors at letter cancellation and reduced the rate of finger tapping (P < 0.05), while oxazepam increased the number of errors and reduced accuracy at continuous attention (P < 0.01), and increased the number of involuntary rest pauses during tapping (P < 0.05). 4. There were no effects of drugs on subjective assessment of mood. 5. No changes in the electrical activity of the brain were observed with bendrofluazide. In recordings with eyes open, oxazepam reduced delta (0.5-3 Hz), theta (3.5-7 Hz) and alpha 2 (10.5-13 Hz) while increasing beta 1 (13.5-21 Hz) activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in the topographical distribution of EEG activity during surgical anaesthesia and on emergence from volatile anesthetics

Computerized processing of a 16 channel EEG allows mapping and display of cortical electrical activity in a useful mode for intraoperative monitoring. We studied the topographical distribution of EEG-activity displayed as spectral maps comparing inhalational anaesthesia with isoflurane or enflurane during surgical anaesthesia and emergence. Two groups of nine patients each were anaesthetized with one of the two regimens. The EEG patterns during steady state end-tidal concentrations of isoflurane (0.7-1.1%) or enflurane (0.8-1.3%) showed highest activity in the frontal and occipital areas. At near awakening the frontal and occipital dominance of delta activity disappeared in both groups and was replaced by homogeneous delta activity over the entire cortex; variations in the topographical distribution of enflurane and isoflurane were recorded in the other spectral bands. We conclude that changes in topographic EEG patterns observed during the transition from surgical anaesthesia to emergence, in particular the disappearance of frontal and occipital dominance of delta activity common to isoflurane and enflurane, may serve to detect undesirably light levels of anaesthesia.