Comparative bioavailability studies with a new mixed-micelles solution of diazepam utilizing radioreceptor assay, psychometry and EEG brain mapping

Directing Amphiphilic Self-Assembly: From Microstructure Control to Interfacial Engineering

The self-assembly of small molecules into complex nanoscale structures is driven by the interplay of various noncovalent interactions. It has now become evident that by maneuvering this intermolecular interaction the geometry and interfacial properties of several nanoscale objects can be tamed. In particular, diverse structures such as spheres, rods, worms, ribbons, and vesicles can be produced by tuning the packing of molecules in the aggregate. Stimuli-sensitive assemblies that can reversibly associate or dissociate in response to environmental changes have been fabricated as model systems for the self-regulated drug delivery vehicle. Surface passivation of inorganic materials can be achieved by the selective organization of molecules at the interface. Such surface functionalization of inorganic materials by organic counterparts provides kinetic stability in biological media and permits the selective binding of active ingredients. Advances made in the area of molecular self-assembly and factors governing such association processes have made it possible to control the interfacial properties and microstructure of nanoscale materials.

Touch Accelerates Visual Awareness

To efficiently interact with the external environment, our nervous system combines information arising from different sensory modalities. Recent evidence suggests that cross-modal interactions can be automatic and even unconscious, reflecting the ecological relevance of cross-modal processing. Here, we use continuous flash suppression (CFS) to directly investigate whether haptic signals can interact with visual signals outside of visual awareness. We measured suppression durations of visual gratings rendered invisible by CFS either during visual stimulation alone or during visuo-haptic stimulation. We found that active exploration of a haptic grating congruent in orientation with the suppressed visual grating reduced suppression durations both compared with visual-only stimulation and to incongruent visuo-haptic stimulation. We also found that the facilitatory effect of touch on visual suppression disappeared when the visual and haptic gratings were mismatched in either spatial frequency or orientation. Together, these results demonstrate that congruent touch can accelerate the rise to consciousness of a suppressed visual stimulus and that this unconscious cross-modal interaction depends on visuo-haptic congruency. Furthermore, since CFS suppression is thought to occur early in visual cortical processing, our data reinforce the evidence suggesting that visuo-haptic interactions can occur at the earliest stages of cortical processing.

Short-term monocular deprivation alters early components of visual evoked potentials

KEY POINTS

Short-term monocular deprivation in adult humans produces a perceptual boost of the deprived eye reflecting homeostatic plasticity. Visual evoked potentials (VEPs) to transient stimuli change after 150 min of monocular deprivation in adult humans. The amplitude of the C1 component of the VEP at a latency of about 100 ms increases for the deprived eye and decreases for the non-deprived eye after deprivation, the two effects being highly negatively correlated. Similarly, the evoked alpha rhythm increases after deprivation for the deprived eye and decreases for the non-deprived eye. The data demonstrate that primary visual cortex excitability is altered by a short period of monocular deprivation, reflecting homeostatic plasticity.

ABSTRACT

Very little is known about plasticity in the adult visual cortex. In recent years psychophysical studies have shown that short-term monocular deprivation alters visual perception in adult humans. Specifically, after 150 min of monocular deprivation the deprived eye strongly dominates the dynamics of binocular rivalry, reflecting homeostatic plasticity. Here we investigate the neural mechanisms underlying this form of short-term visual cortical plasticity by measuring visual evoked potentials (VEPs) on the scalp of adult humans during monocular stimulation before and after 150 min of monocular deprivation. We found that monocular deprivation had opposite effects on the amplitude of the earliest component of the VEP (C1) for the deprived and non-deprived eye stimulation. C1 amplitude increased (+66%) for the deprived eye, while it decreased (-29%) for the non-deprived eye. Source localization analysis confirmed that the C1 originates in the primary visual cortex. We further report that following monocular deprivation, the amplitude of the peak of the evoked alpha spectrum increased on average by 23% for the deprived eye and decreased on average by 10% for the non-deprived eye, indicating a change in cortical excitability. These results indicate that a brief period of monocular deprivation alters interocular balance in the primary visual cortex of adult humans by both boosting the activity of the deprived eye and reducing the activity of the non-deprived eye. This indicates a high level of residual homeostatic plasticity in the adult human primary visual cortex, probably mediated by a change in cortical excitability.

Neuronal network pharmacodynamics of GABAergic modulation in the human cortex determined using pharmaco-magnetoencephalography

Neuronal network oscillations are a unifying phenomenon in neuroscience research, with comparable measurements across scales and species. Cortical oscillations are of central importance in the characterization of neuronal network function in health and disease and are influential in effective drug development. Whilst animal in vitro and in vivo electrophysiology is able to characterize pharmacologically induced modulations in neuronal activity, present human counterparts have spatial and temporal limitations. Consequently, the potential applications for a human equivalent are extensive. Here, we demonstrate a novel implementation of contemporary neuroimaging methods called pharmaco‐magnetoencephalography. This approach determines the spatial profile of neuronal network oscillatory power change across the cortex following drug administration and reconstructs the time course of these modulations at focal regions of interest. As a proof of concept, we characterize the nonspecific GABAergic modulator diazepam, which has a broad range of therapeutic applications. We demonstrate that diazepam variously modulates θ (4–7 Hz), α (7–14 Hz), β (15–25 Hz), and γ (30–80 Hz) frequency oscillations in specific regions of the cortex, with a pharmacodynamic profile consistent with that of drug uptake. We examine the relevance of these results with regard to the spatial and temporal observations from other modalities and the various therapeutic consequences of diazepam and discuss the potential applications of such an approach in terms of drug development and translational neuroscience. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.

EEG topography and tomography (LORETA) in the classification and evaluation of the pharmacodynamics of psychotropic drugs

By multi-lead computer-assisted quantitative analyses of human scalp-recorded electroencephalogram (QEEG) in combination with certain statistical procedures (quantitative pharmaco-EEG) and mapping techniques (pharmaco-EEG mapping or topography), it is possible to classify psychotropic substances and objectively evaluate their bioavailability at the target organ, the human brain. Specifically, one may determine at an early stage of drug development whether a drug is effective on the central nervous system (CNS) compared with placebo, what its clinical efficacy will be like, at which dosage it acts, when it acts and the equipotent dosages of different galenic formulations. Pharmaco-EEG maps of neuroleptics, antidepressants, tranquilizers, hypnotics, psychostimulants and nootropics/cognition-enhancing drugs will be described. Methodological problems, as well as the relationships between acute and chronic drug effects, alterations in normal subjects and patients, CNS effects and therapeutic efficacy will be discussed. Imaging of drug effects on the regional brain electrical activity of healthy subjects by means of EEG tomography such as low-resolution electromagnetic tomography (LORETA) has been used for identifying brain areas predominantly involved in psychopharmacological action. This will be shown for the representative drugs of the four main psychopharmacological classes, such as 3 mg haloperidol for neuroleptics, 20 mg citalopram for antidepressants, 2 mg lorazepam for tranquilizers and 20 mg methylphenidate for psychostimulants. LORETA demonstrates that these psychopharmacological classes affect brain structures differently. By considering these differences between psychotropic drugs and placebo in normal subjects, as well as between mental disorder patients and normal controls, it may be possible to choose the optimum drug for a specific patient according to a key-lock principle, since the drug should normalize the deviant brain function. Thus, pharmaco-EEG topography and tomography are valuable methods in human neuropsychopharmacology, clinical psychiatry and neurology.

PEG-based micelles as carriers of contrast agents for different imaging modalities

The review deals with the fast growing field of diagnostic micelles. The need and requirements for microparticulate contrast agents are discussed. Brief analysis of the micellization process and micelle properties shows that micelles made of amphiphilic co-polymers seem to be the most attractive for practical application. These micelles can be prepared from the variety of co-polymers including hydrophilic polymers grafted on one terminus with lipid residues. Polymeric micelles are considered loaded or modified with various contrast reporter moieties for gamma-scintigraphy, magnetic resonance imaging (MRI), and computed tomography (CT). Their in vitro and in vivo properties are discussed and the results of the initial animal experiments are presented. Mixed micelles were prepared from diacyllipid-polyethylene glycol (PEG) conjugates and polymeric amphiphilic chelates, containing entrapped metals, such as 111-In or Gd, and used for the experimental gamma- and MR imaging of various components of lymphatic system in rabbits. The method is also described to prepare polymeric iodine-containing PEG-based micelles which may act as a long-circulating blood pool imaging agent for CT. Experimental CT-imaging performed in mice and rabbits demonstrated high potential of a micellar contrast agent.

Structure and design of polymeric surfactant-based drug delivery systems

The review concentrates on the use of polymeric micelles as pharmaceutical carriers. Micellization of biologically active substances is a general phenomenon that increases the bioavailability of lipophilic drugs and nutrients. Currently used low-molecular-weight pharmaceutical surfactants have low toxicity and high solubilization power towards poorly soluble pharmaceuticals. However, micelles made of such surfactants usually have relatively high critical micelle concentration (CMC) and are unstable upon strong dilution (for example, with the blood volume upon intravenous administration). On the other hand, amphiphilic block co-polymers are also known to form spherical micelles in solution. These micelles have very high solubilization capacity and rather low CMC value that makes them very stable in vivo. Amphiphilic block co-polymers suitable for micelle preparation are described and various types of polymeric micelles are considered as well as mechanisms of their formation, factors influencing their stability and disintegration, their loading capacity towards various poorly soluble pharmaceuticals, and their therapeutic potential. The basic mechanisms underlying micelle longevity and steric protection in vivo are considered with a special emphasis on long circulating drug delivery systems. Advantages and disadvantages of micelles when compared with other drug delivery systems are considered. New polymer-lipid amphiphilic compounds such as diacyillipid-polyethylene glycol, are described and discussed. These compounds are very attractive from a practical point of view, since they easily micellize yielding extremely stable micelles with very high loading capacity. Micelle passive accumulation in the areas with leaky vasculature (tumors, infarct zones) is discussed as an important physiology-based mechanism of drug delivery into certain target zones. Targeted polymeric micelles prepared by using thermo- or pH-sensitive components or by attaching specific targeted moieties (such as antibodies) to their outer surface are described as well as their preparation and some in vivo properties. The fast growing field of diagnostic micelles is analyzed. Polymeric micelles are considered loaded with various agents for gamma, magnetic resonance, and computed tomography imaging. Their in vitro and in vivo properties are discussed and the results of the initial animal experiments are presented.

Nonorganic insomnia in panic Disorder: comparative sleep laboratory studies with normal controls and placebo-controlled trials with alprazolam

Objective and subjective sleep and awakening quality was investigated in 11 drug-free patients (4 females, 7 males) aged 30-55 (mean: 44+/-9) years with nonorganic insomnia (F 51.0) related to panic disorder (F 41.0) as compared with 11 age- and sex-matched normal controls aged 30-58 (mean: 44+/-9) years, utilising polysomnography (PSG) and psychometry. PSG demonstrated decreased sleep efficiency (primary target variable), total sleep time (TST) and S2 as well as increased middle and late insomnia, S1, S3+S4, snoring and PLM in patients. There were no intergroup differences in REM variables. Subjective sleep quality deteriorated, as did drive and fine motor activity in the morning, while concentration increased. Blood pressure in the evening and morning and pulse rate in the evening were elevated. These differences as compared with normals were distinct from those observed in other sleep disorders. In a subsequent acute, placebo-controlled cross-over design study, patients received alprazolam 0.5 mg (Xanor((R));) and placebo. As compared with placebo, alprazolam induced an increase in sleep efficiency (primary target variable), TST and S2, a decrease in wakefulness during the total sleep period, S3+S4 and the oxygen desaturation and PLM indices, and improved subjective sleep quality, somatic complaints, drive, affectivity and drowsiness in the morning. There were no changes in REM variables. Thus, alprazolam induced changes that were opposite to the differences observed between patients and controls before treatment, thereby normalizing sleep and awakening quality. As observed in insomnia related to GAD and subsequent benzodiazepine therapy, the present study also points to a key-lock principle in the treatment of insomnia caused by anxiety disorders and neurophysiologically visualizes processes at the receptor level (e.g. benzodiazepine agonists versus inverse agonists). Copyright 2000 John Wiley & Sons, Ltd.

Effects of intravenous diazepam pretreatment on lactate-induced panic

The psychological and physiological effects of acute low-potency benzodiazepine administration on lactate-induced panic were examined in 10 patients with panic disorder (PD). The patients, who had panicked during a standard sodium-lactate infusion, underwent a repeat infusion modified by pretreatment with intravenous diazepam (5 mg). Acute Panic Inventory (API) scores preceding the second lactate infusion, which were associated with diazepam pretreatment, were significantly reduced in compared with those measured before the first lactate infusion. However, the second visit "fear of doom" item of the API was significantly reduced relative to the same time point of the first visit 35 min before lactate infusion, when diazepam had not yet been administered. Thus, the reduction of prelactate anxiety preceding the second infusion appeared to reflect both pharmacological and nonpharmacological contributions. The diazepam pretreatment condition was associated with a significantly increased infusion duration and a significant attenuation of rate of API symptom increase in response to lactate. Despite significant attenuation of lactate infusion effects associated with the diazepam pretreatment condition, 7 of 10 patients experienced a second panic attack. This pilot study suggests that diazepam pretreatment is associated with a marked reduction of symptomatic response during a second lactate infusion, although the magnitude of attenuation observed was insufficient to block lactate-induced panic in a majority of lactate-vulnerable PD patients.

Frequency domain source localization shows state-dependent diazepam effects in 47-channel EEG

The topic of this study was to evaluate state-dependent effects of diazepam on the frequency characteristics of 47-channel spontaneous EEG maps. A novel method, the FFT-Dipole-Approximation (Lehmann and Michel, 1990), was used to study effects on the strength and the topography of the maps in the different frequency bands. Map topography was characterized by the 3-dimensional location of the equivalent dipole source and map strength was defined as the spatial standard deviation (the Global Field Power) of the maps of each frequency point. The Global Field Power can be considered as a measure of the amount of energy produced by the system, while the source location gives an estimate of the center of gravity of all sources in the brain that were active at a certain frequency. State-dependency was studied by evaluating the drug effects before and after a continuous performance task of 25 min duration. Clear interactions between drug (diazepam vs. placebo) and time after drug intake (before and after the task) were found, especially in the inferior-superior location of the dipole sources. It supports the hypothesis that diazepam, like other drugs, has different effects on brain functions depending on the momentary functional state of the brain. In addition to the drug effects, clearly different source locations and Global Field Power were found for the different frequency bands, replicating earlier reports (Michel et al., 1992).

Pharmacokinetic and -dynamic studies with a new anxiolytic, suriclone, utilizing EEG mapping and psychometry

1. In a double-blind, placebo-controlled, cross-over study, acute pharmacokinetic, neurophysiological and psychotropic effects of suriclone, a new cyclopyrrolone derivative, were investigated and compared with alprazolam. 2. Fifteen normal young volunteers received randomized oral single doses of placebo, 0.1, 0.2 and 0.4 mg suriclone as well as 1 mg alprazolam as reference compound. Investigations were carried out before and 1, 2, 4, 6 and 8 h after drug administration. 3. Pharmacokinetic investigations by radioimmunoassay showed a dose-dependent fast rise of plasma concentrations with a peak at 1 h and a rapid decline thereafter. Both the Cmax and the AUC values exhibited a linear relationship to dose. 4. EEG brain mapping demonstrated significant CNS effects of both compounds, characteristic for tranquillizers (increase of beta, decrease of alpha and increase of delta activity; attenuation of total power and acceleration of the centroid, i.e. centre of gravity frequency). When compared with alprazolam, suriclone exerted less sedative effects. 5. Time-efficacy calculations showed the pharmacodynamic peak effect of suriclone from the 2nd to the 4th hour, and of alprazolam in the 1st hour. Dose-efficacy calculations showed that the most pronounced CNS changes occurred after 1 mg alprazolam, followed by 0.4, 0.2 and 0.1 mg suriclone. 6. Psychometric investigations demonstrated no significant effects after the two lower doses of suriclone, while 0.4 mg and 1 mg alprazolam induced a decrement both in noopsychic and thymopsychic variables seen after higher doses of anxiolytic sedatives. Psychophysiology (critical flicker fusion, pupillometry, and skin conductance measures) pulse rate, systolic and diastolic blood pressure remained unchanged. 7. Psychophysiology (critical flicker fusion, pupillometry and skin conductance measures) showed differential dose-dependent effects. Pulse rate, systolic and diastolic blood pressure remained unchanged. Anxiolytic-characteristic side-effects (tiredness, drowsiness, etc.) occurred predominantly after the highest doses 0.4 mg suriclone and 1 mg alprazolam.

[Effects of cyclandelate on the CNS--a double-blind, placebo-controlled study of healthy subjects]

The effect of cyclandelate (Natil) on the CNS was tested in a double-blind, placebo-controlled pilot study on 48 healthy males using a single oral dosage of 1200 mg. The EEG was evaluated quantitatively by spectral analysis before and one hour as well as two and a half hours after drug or placebo administration under resting conditions and while performing a test of mental arithmetic. Under resting conditions the power in the alpha 2 frequency band of the signals from the frontal and central recordings was increased in the cyclandelate group in comparison to the placebo group. This effect was still observed two and a half hours after drug intake. Under the condition of mental arithmetic no drug related effect was observed in the EEG. The cyclandelate induced increase of spectral power in the alpha 2 frequency band under resting conditions demonstrates a general effect of cyclandelate on the CNS. The results are discussed with respect to the known age related decrease of spectral power in the alpha frequency band. The established effect of cyclandelate in young healthy subjects calls for a study with chronic treatment in elderly subjects or patients with cognitive deficits.

Inhibition of amphotericin B (Fungizone) toxicity to cells by egg lecithin-glycocholic acid mixed micelles

Mixed micelles prepared from egg lecithin and the sodium salt of glycocholic acid markedly inhibited amphotericin B toxicity to mammalian cells without significantly affecting the antifungal effects of the drug.