Interaction of central and peripheral benzodiazepine sites in benzodiazepine tolerance and discontinuation

Characterization of pharmaco-EEG fingerprint and sleep-wake profiles of Lavandula angustifolia Mill. essential oil inhalation and diazepam administration in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Lavandula angustifolia Mill. Essential oil (Lavender EO) has a long history of medicinal use and is particularly claimed to possess anxiolytic and sedative properties. Lavender EO aromatherapy has been used to reduce distress and improve insomnia naturally. Increasing evidence appeared to show similarities between the effects of lavender EO and the anxiolytic drugs, benzodiazepines. However, its effects on sleep-wake and electrical brain patterns in comparison to that of the standard anxiolytic, diazepam, remained to be explored.

AIM OF THE STUDY

The aim of this work was to investigate electroencephalography (EEG) profiles and sleep-pattern elicited by lavender EO inhalation compared to that of diazepam, a standard anxiolytic drug in in vivo rat model.

MATERIALS AND METHODS

Adult male Wistar rats were anesthetized for electrode implantation on the frontal and parietal skulls. EEG signals were recorded for 180 min following intraperitoneal injection of diazepam (10 mg/kg) or during continuous inhalation of lavender EO (200 μL) or distilled water (control). Fast Fourier transform was used for the analyses of EEG power spectra and sleep-wake parameters.

RESULTS

During a 30-60 min period, diazepam and lavender EO significantly increased frontal powers of 0.78-45.31 and 7.03-18.36 Hz, respectively. Both treatments also increased parietal powers with lower magnitudes of significant change. Significant increases in some frequency ranges remained until a 60-90 min period. Sleep-wake analyses also revealed that diazepam significantly reduced time spent in wake, increased time spent in non-rapid eye movement (NREM), increased episode duration of NREM, decreased numbers of wake episode and decreased rapid eye movement (REM) sleep latency. On the other hand, lavender EO only significantly decreased wake episodes and latency to REM sleep. Lavender EO inhalation reduced numbers of wake episode but maintain normal time spent in wake, NREM and REM sleeps.

CONCLUSIONS

These findings might suggest beneficial and distinct anxiolytic-like effects of lavender EO for sleep enhancing purposes.

Dose-effect study of Gelsemium sempervirens in high dilutions on anxiety-related responses in mice

INTRODUCTION

This study was designed to investigate the putative anxiolytic-like activity of ultra-low doses of Gelsemium sempervirens (G. sempervirens), produced according to the homeopathic pharmacopeia.

METHODS

Five different centesimal (C) dilutions of G. sempervirens (4C, 5C, 7C, 9C and 30C), the drug buspirone (5 mg/kg) and solvent vehicle were delivered intraperitoneally to groups of ICR-CD1 mice over a period of 9 days. The behavioral effects were assessed in the open-field (OF) and light-dark (LD) tests in blind and randomized fashion.

RESULTS

Most G. sempervirens dilutions did not affect the total distance traveled in the OF (only the 5C had an almost significant stimulatory effect on this parameter), indicating that the medicine caused no sedation effects or unspecific changes in locomotor activity. In the same test, buspirone induced a slight but statistically significant decrease in locomotion. G. sempervirens showed little stimulatory activity on the time spent and distance traveled in the central zone of the OF, but this effect was not statistically significant. In the LD test, G. sempervirens increased the % time spent in the light compartment, an indicator of anxiolytic-like activity, with a statistically significant effect using the 5C, 9C and 30C dilutions. These effects were comparable to those of buspirone. The number of transitions between the compartments of the LD test markedly increased with G. sempervirens 5C, 9C and 30C dilutions.

CONCLUSION

The overall pattern of results provides evidence that G. sempervirens acts on the emotional reactivity of mice, and that its anxiolytic-like effects are apparent, with a non-linear relationship, even at high dilutions.

Diazepam-treated female rats: flumazenil- and PK 11195-induced withdrawal in the hippocampus CA1

Six female rats had a loading dose of 180 mg of diazepam (DZ) contained in two Silastic capsules implanted in their backs. Thereafter, a single 90-mg capsule was implanted weekly for 4 weeks prior to weekly microinjections of 1 microl of flumazenil (6.25, 12.5, or 25 microg) and PK 11195 (3.125, 6.25, or 12.5 microg) or vehicle into the CA1. Three control rats had empty capsules implanted but received only the high dose of flumazenil after 5 weeks. The time of DZ exposure spanned 8 weeks. Mean steady-state plasma levels of DZ were 1.06 +/- 0.11, and the mean total (DZ + metabolites) was 2.46 microg/ml +/- 0.37. Flumazenil elicited a dose-related precipitated withdrawal score (PAS) in DZ-treated rats (but not in controls) characterized by dose-related increases in convulsive (twitches and jerks), motor and autonomic signs, dose-related increases in the percent of total power in the low frequency (1-4 Hz), and decreases in the high-frequency (18-26 Hz) bands of the EEG recorded from the dentate and the amygdala. PK 11195 produced a dose-related increase in the 4-12 Hz band of the EEG recorded from the CA1, whereas the PAS was mild and not dose-related. However, the 6.25 and 12.5-microg doses elicited a significant PAS that tended to increase with dose. These data indicate that chronic DZ produces dependence, and that in the CA1 it involves the participation of central and possibly peripheral benzodiazepine (BZ) receptors located within this structure.

Abnormal peripheral benzodiazepine receptor density associated with generalized social phobia

BACKGROUND

Peripheral benzodiazepine receptors (PBRs) are involved in regulating stress responses. Abnormally low numbers of platelet PBRs have been found in patients with panic disorder, posttraumatic stress disorder, and generalized anxiety disorder, but not in patients with obsessive-compulsive disorder (OCD) or major depressive disorder (MDD). The purpose of this study was to evaluate the PBR density on platelets from patients with generalized social phobia (GSP).

METHODS

The density (Bmax) and dissociation constant (Kd) of platelet PBRs was determined for 53 medication-free patients with GSP and an equal number of control subjects (NC).

RESULTS

The GSP group was found to have a significantly lower PBR Bmax than the NC group (GSP = 2764 +/- 1242 vs. NC = 4327 +/- 1850 fmol/mg protein, df = 1,100, F = 22.7, p = .00001).

CONCLUSIONS

GSP shares this PBR abnormality with some other anxiety disorders but not with OCD or MDD. PBRs may play a role in the pathophysiology of some anxiety disorders.

Carbamazepine normalizes the altered behavioral and neurochemical response to stress in benzodiazepine-withdrawn rats

Rats chronically treated with diazepam (2 mg/kg per day, i.p.) for 21 days were tested 96 h after the last injection in both the forced swim test (inescapable stress) and in an active avoidance test (escapable stress). The influence of carbamazepine (7.5 mg/kg, i.p.) administered 25 min prior to each behavioral task was investigated. Withdrawn animals showed a reduced time spent in immobility in the forced swim test and an enhanced latency to escape in the active avoidance test. Both behavioral effects were normalized by a single carbamazepine administration. An additional experiment was performed to investigate the effect of a forced swim experience on cortical chloride uptake following GABA (gamma-aminobutyric acid) stimulation 96 h after diazepam withdrawal, and the influence of a single administration of carbamazepine on these effects. An increased chloride uptake was observed in vehicle-treated rats but not in diazepam-withdrawn animals following the swimming experience. Carbamazepine pretreatment enhanced chloride uptake after diazepam withdrawal but did not modify chloride flux in stressed or unstressed vehicle-treated rats. These results support the hypothesis that diazepam withdrawal affects the ability to develop adaptive responses to stress and that carbamazepine can normalize such an alteration.