Mobility behaviour and driving status of patients with mental disorders - an exploratory study.

BACKGROUND: Driving is an important activity of daily life and an integral part of mobility. However, impact of mental illness on road mobility is widely unexplored. METHOD: Driving status in 1497 psychiatric inpatients (PPs) and a clinical control group of 313 neurological inpatients (NPs) was investigated using a brief questionnaire. RESULTS: 67% of PPs (89% NPs) reported to have a valid driver's licence and 77% of them (92% NPs) reported to regularly use their cars. Within driver's license holders, patients with organic mental disorder (32%), substance dependence (37%) and psychotic disorder (40%) had the lowest proportion of current drivers. Higher educational qualification (odds ratio [OR] from 2.978 to 17.036) and being married/partnered (OR 3.049) or divorced (OR 4.840) significantly advanced the probability of possession of a driving license. Predictive factors for driving cessation were being female, an older age, drawing a pension and having an organic mental disease or schizophrenic disorder. CONCLUSION: Mental disease has a negative impact on driving status and this is especially true for illnesses frequently being accompanied by distinct cognitive impairments. Factors predicting road mobility elucidate the strong relationship with psychosocial status indicating that recovery of driving competence should be an integral goal of treatment strategies.

Monitoring CSF proteome alterations in amyotrophic lateral sclerosis: obstacles and perspectives in translating a novel marker panel to the clinic.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a fatal disorder of the motor neuron system with poor prognosis and marginal therapeutic options. Current clinical diagnostic criteria are based on electrophysiological examination and exclusion of other ALS-mimicking conditions. Neuroprotective treatments are, however, most promising in early disease stages. Identification of disease-specific CSF biomarkers and associated biochemical pathways is therefore most relevant to monitor disease progression, response to neuroprotective agents and to enable early inclusion of patients into clinical trials. METHODS AND FINDINGS: CSF from 35 patients with ALS diagnosed according to the revised El Escorial criteria and 23 age-matched controls was processed using paramagnetic bead chromatography for protein isolation and subsequently analyzed by MALDI-TOF mass spectrometry. CSF protein profiles were integrated into a Random Forest model constructed from 153 mass peaks. After reducing this peak set to the top 25%, a classifier was built which enabled prediction of ALS with high accuracy, sensitivity and specificity. Further analysis of the identified peptides resulted in a panel of five highly sensitive ALS biomarkers. Upregulation of secreted phosphoprotein 1 in ALS-CSF samples was confirmed by univariate analysis of ELISA and mass spectrometry data. Further quantitative validation of the five biomarkers was achieved in an 80-plex Multiple Reaction Monitoring mass spectrometry assay. CONCLUSIONS: ALS classification based on the CSF biomarker panel proposed in this study could become a valuable predictive tool for early clinical risk stratification. Of the numerous CSF proteins identified, many have putative roles in ALS-related metabolic processes, particularly in chromogranin-mediated secretion signaling pathways. While a stand-alone clinical application of this classifier will only be possible after further validation and a multicenter trial, it could be readily used to complement current ALS diagnostics and might also provide new insights into the pathomechanisms of this disease in the future.

[Diagnosis and treatment of amyotrophic lateral sclerosis]. / Paresen-Muskelatrophien-Spastik: Denken Sie an die amyotrophe Lateralsklerose.

Like Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease in which a very defined population of neurons selectively degenerates. Muscular atrophy and central paresis develop in ALS patients relatively quickly--usually within months to a few years. Bulbar symptoms such as swallowing disorders and dysarthria are frequently observed in the beginning. The disease progresses steadily and without remission. The average length of survival after diagnosis is two to three years. The diagnosis is made on the basis of a characteristic group of symptoms and confirmed or substantiated through additional clinical neurological tests. Currently, the cause of the disease cannot be treated. Treatment concentrates primarily on symptomatic measures and providing supportive devices.

Correlation between distal motor latency and compound muscle action potential in amyotrophic lateral sclerosis.

OBJECTIVES: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder, characterized by a selective progressive degeneration of the motor system. Electromyography is essential for the diagnosis of ALS. The measurement of motor conduction of peripheral nerves is of major importance to recognize other possible causes of progressive muscle wasting. However, there are also pathologic changes in nerve conduction studies in ALS patients. METHODS: In this study we analysed the values of distal motor latency (DML), compound muscle action potential (CMAP) and motor nerve conduction velocity (MNCV) in 95 patients with definite ALS. RESULTS: We found slight slowing of MNCV and moderate to strong reduction of CMAP and a prolongation of DML. We found no significant correlation between MNCV and CMAP. DISCUSSION: The main finding of the present work was the negative correlation between DML and CMAP. It is interpreted as a very distal axonal damage as the main reason for prolongation of DML in ALS patients.

GABA(A)-receptor mRNA expression in the prefrontal and temporal cortex of ALS patients.

There is evidence that excitotoxic cell death is involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). Electrophysiological and histological studies support the pathophysiological concept of an impaired inhibitory, namely GABAergic, control of the motoneurons in the cerebral cortex of ALS patients. Recently, pathological, neuropsychological and functional imaging data have challenged the view that ALS is a disorder restricted to the motor system. The aim of our study was to investigate the expression of the most abundant GABA(A)-receptor subunit mRNAs and the GABA synthesizing enzyme glutamic acid decarboxylase (GAD) in the prefrontal, temporal, occipital and cerebellar cortex of ALS patients compared to tissue of control persons. We performed in situ hybridization histochemistry (ISH) on human post-mortem cortex sections of ALS patients (n=5) and age-matched controls with no history of neurological disease (n=5). In the prefrontal and temporal cortex of ALS patients, we detected significantly reduced mRNA expression of the alpha1-subunit, while the GABA synthesizing enzyme glutamic acid decarboxylase (GAD) was significantly upregulated in these regions. In the occipital and cerebellar cortex, we did not see disease-specific differences of the mRNA expression of the investigated subunits.

A mutation in the GABA(A) receptor alpha(1)-subunit is associated with absence epilepsy.

OBJECTIVE: To detect mutations in GABRA1 in idiopathic generalized epilepsy. METHODS: GABRA1 was sequenced in 98 unrelated idiopathic generalized epilepsy patients. Patch clamping and confocal imaging was performed in transfected mammalian cells. RESULTS: We identified the first GABRA1 mutation in a patient with childhood absence epilepsy. Functional studies showed no detectable GABA-evoked currents for the mutant, truncated receptor, which was not integrated into the surface membrane. INTERPRETATION: We conclude that this de novo mutation can contribute to the cause of "sporadic" childhood absence epilepsy by a loss of function and haploinsufficiency of the GABA(A) receptor alpha(1)-subunit, and that GABRA1 mutations rarely are associated with idiopathic generalized epilepsy.

Selective and nonselective benzodiazepine agonists have different effects on motor cortex excitability.

Transcranial magnetic stimulation (TMS) is a useful method to study pharmacological effects on motor cortex excitability. Zolpidem is a selective agonist of the benzodiazepine receptor subtype BZ1 and has a distinct pharmacological profile compared to diazepam. To study the different effects of these two drugs on the cortical inhibitory system, TMS was performed before and after administration of a single oral dose of zolpidem (10 mg) and diazepam (5 mg) in six healthy volunteers. TMS tests included the determination of resting and active motor threshold (MT) and measurements of the amplitudes of motor evoked potentials, intracortical facilitation (ICF), short-latency intracortical inhibition (SICI), and long-latency intracortical inhibition (LICI), and determination of the cortical silent period (CSP). Both drugs were without effect on the active or resting MT and decreased the ICF. Prolongation of the CSP and enhancement of LICI only in the presence of zolpidem point to a specific BZ1-related mechanism underlying the long-lasting component of cortical inhibition. This selective modulation of the CSP and the LICI points to a specific role of BZ1 receptors in the control of inhibitory neuronal loops within the primary motor cortex.

Molecular analysis of the interaction of the pyrazine derivatives RPR119990 and RPR117824 with human AMPA-type glutamate receptor channels.

Antagonizing glutamatergic neurotransmission by blockade of AMPA-type glutamate receptors is a promising pharmacological strategy in the treatment of neurodegenerative diseases. We investigated the interaction of two new pyrazine derivatives (RPR119990 and RPR117824) with recombinant AMPA-type glutamate receptors. Recombinant homooligomeric GluR1flop, GluR2flip, GluR2flop, GluR6, non-desensitizing GluR2 L504Y channels and heterooligomeric GluR1/2 channels were expressed in HEK293 cells. AMPA-type channels were competitively inhibited by RPR119990 or RPR117824 with an IC(50) around 10 nM, at GluR6 channels the dose-response relation of the inhibition was shifted to higher concentrations. Non-desensitizing GluR2 L504Y channels were used to further characterize the inhibition. After equilibration with the agonist a marked dose-dependent current decay upon coapplication of glutamate and RPR119990 and a dose-independent time course of recovery from block was observed. The extents of current inhibition as well as the time constant of current decay upon addition of the blocker to the test solution were dependent on agonist concentration, pointing to a competitive inhibition. Quantitative analysis of the experimental data using computerized simulations are compatible with a competitive block mechanism and provides hints to binding sites at unliganded and liganded closed states of the receptor.

Dopaminergic properties and function after grafting of attached neural precursor cultures.

Generation of dopaminergic (DA) neurons from multipotent embryonic progenitors represents a promising therapeutical strategy for Parkinson's disease (PD). Aim of the present study was the establishment of enhanced cell culture conditions, which optimize the use of midbrain progenitor cells in animal models of PD. In addition, the progenitor cells were characterized during expansion and differentiation according to morphological and electrophysiological criteria and compared to primary tissue. Here, we report that CNS precursors can be expanded in vitro up to 40-fold and afterwards be efficiently differentiated into DA neurons. After 4-5 days under differentiation conditions, more than 70% of the neurons were TH+, equivalent to 30% of the total cell population. Calcium imaging revealed the presence of calcium-permeable AMPA receptors in the differentiated precursors which are capable to contribute to many developmental processes. The overall survival rate, degree of reinnervation and the behavioral performance after transplantation of 4 days in-vitro-differentiated cells were similar to results after direct grafting of E14 ventral mesencephalic cells, whereas after shorter or longer differentiation periods, respectively, less effects were achieved. Compared to the amount of in-vitro-generated DA neurons, the survival rate was only 0.8%, indicating that these cells are very vulnerable. Our results suggest that expanded and differentiated DA precursors from attached cultures can survive microtransplantation and integrate within the striatum in terms of behavioral recovery. However, there is only a short time window during in vitro differentiation, in which enough cells are already differentiated towards a DA phenotype and simultaneously not too mature for implantation. However, additional factors and/or genetical manipulation of these expanded progenitors will be required to increase their in vivo survival in order to improve both the ethical and the technical outlook for the use of fetal tissue in clinical transplantation.

Molecular analysis of the A322D mutation in the GABA receptor alpha-subunit causing juvenile myoclonic epilepsy.

Juvenile myoclonic epilepsy (JME) belongs to the most common forms of hereditary epilepsy, the idiopathic generalized epilepsies. Although the mode of inheritance is usually complex, mutations in single genes have been shown to cause the disease in some families with autosomal dominant inheritance. The first mutation in a multigeneration JME family has been recently found in the alpha1-subunit of the GABAA receptor (GABRA1), predicting the single amino acid substitution A322D. We further characterized the functional consequences of this mutation by coexpressing alpha1-, beta2- and gamma2-subunits in human embryonic kidney (HEK293) cells. By using an ultrafast application system, mutant receptors have shown reduced macroscopic current amplitudes at saturating GABA concentrations and a highly reduced affinity to GABA compared to the wild-type (WT). Dose-response curves for current amplitudes, activation kinetics, and GABA-dependent desensitization parameters showed a parallel shift towards 30- to 40-fold higher GABA concentrations. Both deactivation and resensitization kinetics were considerably accelerated in mutant channels. In addition, mutant receptors labelled with enhanced green fluorescent protein (EGFP) were not integrated in the cell membrane, in contrast to WT receptors. Therefore, the A322D mutation leads to a severe loss-of-function of the human GABAA receptor by several mechanisms, including reduced surface expression, reduced GABA-sensitivity, and accelerated deactivation. These molecular defects could decrease and shorten the resulting inhibitory postsynaptic currents (IPSCs) in vivo, which can induce a hyperexcitability of the postsynaptic membrane and explain the occurrence of epileptic seizures.

3,4-Methylenedioxymethamphetamine (ecstasy) activates skeletal muscle nicotinic acetylcholine receptors.

Adverse 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) effects are usually ascribed to neurotransmitter release in the central nervous system. Since clinical features such as fasciculations, muscle cramps, rapidly progressing hyperthermia, hyperkalemia, and rhabdomyolysis point to the skeletal muscle as additional target, we studied the effects of MDMA on native and cultured skeletal muscle. We addressed the question whether malignant hyperthermia (MH)-susceptible (MHS) muscle is predisposed to adverse MDMA reactions. Force measurements on muscle strips showed that 100 microM MDMA, a concentration close to that determined in some MDMA users, regularly enhanced the sensitivity of skeletal muscle to caffeine-induced contractures but did not cause contractures on its own. The left-shift of the dose-response curve induced by MDMA was greater in normal than in MHS muscle. Furthermore, MDMA did not release Ca(2+) from isolated sarcoplasmic reticulum vesicles. These findings do not support the view of an MH-triggering effect on muscle. However, MDMA induced Ca(2+) transients in myotubes and increased their acidification rate. Surprisingly, alpha-bungarotoxin, a specific antagonist of the nicotinic acetylcholine receptor (nAChR), abolished these MDMA effects. The nAChR agonistic action of MDMA was confirmed by patch-clamp measurements of ion currents on human embryonic kidney cells expressing nAChR. We conclude that the neuromuscular junction is a target of MDMA and that an activation of nAChR contributes to the muscle-related symptoms of MDMA users. The drug may be of particular risk in individuals with abundant extrajunctional nAChR such as in generalized denervation or muscle regeneration processes and may act on central nAChR.

Structural features of phenol derivatives determining potency for activation of chloride currents via alpha(1) homomeric and alpha(1)beta heteromeric glycine receptors.

Phenol derivatives constitute a family of neuroactive compounds. The aim of our study was to identify structural features that determine their modulatory effects at glycine receptors. We investigated the effects of four methylated phenol derivatives and two halogenated analogues on chloride inward currents via rat alpha(1) and alpha(1)beta glycine receptors, heterologously expressed in HEK 293. All compounds potentiated the effect of a submaximal glycine concentration in both alpha(1) homomeric and alpha(1)beta glycine receptors. While the degree of maximum potentiation of the glycine 10 microM effect in alpha(1)beta receptors was not different between the compounds, the halogenated compounds achieved half-maximum potentiating effects in the low microM range -- at more than 20-fold lower concentrations compared with their nonhalogenated analogues (P<0.0001). The coactivating effect was over-ridden by inhibitory effects at concentrations >300 microM in the halogenated compounds. Neither the number nor the position of the methyl groups significantly affected the EC(50) for coactivation. Only the bimethylated compounds 2,6 and 3,5 dimethylphenol (at concentrations >1000 microM) directly activated both alpha(1) and alpha(1)beta receptors up to 30% of the maximum response evoked by 1000 microM glycine. These results show that halogenation in the para position is a crucial structural feature for the potency of a phenolic compound to positively modulate glycine receptor function, while direct activation is only seen with high concentrations of compounds that carry at least two methyl groups. The presence of the beta subunit is not required for both effects.

Preferred mexiletine block of human sodium channels with IVS4 mutations and its pH-dependence.

The effects of extracellular pH (6.2, 7.4 and 8.2) and 0.1 mM mexiletine, a channel blocker of the lidocaine type, are studied on two mutations of the fourth voltage sensor of the Nav1.4 sodium channel, R1448H/C. The fast inactivated channel state to which mexiletine preferentially binds is destabilized by the mutations. By contrast to the expected low response of R1448H/C carriers, mexiletine is particularly effective in preventing exercise-induced stiffness and paralysis from which these patients suffer. Our measurements performed in the whole-cell mode on stably transfected HEK cells show for the first time that the mutations strikingly accelerate closed-state inactivation and, as steady-state fast inactivation is shifted to more negative potentials, stabilize the fast inactivated channel state in the potential range around the resting potential. At pH 7.4 and 8.2, the phasic mexiletine block is larger for R1448C (55%) and R1448H (47%) than for wild-type channels (31%) due to slowed recovery from block (tau is approximately 520 ms for R1448C versus 270 ms for wild-type at pH 7.4) although the recovery from inactivation is slightly faster for the mutants (tau is approximately 1.9 ms for R1448C versus 3.8 ms for wild-type at pH 7.4). At pH 6.2, recovery from block is relatively fast (tau is approximately 35 ms for R1448H/C and 14 ms for wild-type) and thus shows no use-dependence. We conclude that enhanced closed-state inactivation expands the concept of a mutation-induced uncoupling of channel inactivation from activation to a new potential range and that the higher mexiletine efficacy in R1448H/C carriers compared to other myotonic patients offers a pharmacogenetic strategy for mutation-specific treatment.

Two mechanisms of action of the adamantane derivative IEM-1460 at human AMPA-type glutamate receptors.

1. Antagonizing glutamatergic neurotransmission by blockade of AMPA-type glutamate receptors (GluR) is a promising pharmacological strategy for neuroprotection in neurodegenerative diseases and acute treatment of stroke. 2. We investigated the interaction of the adamantane derivative IEM-1460 with human wild-type and mutant AMPA-type GluR channels. Different recombinant homooligomeric human AMPA-type GluR channels and a rat nondesensitizing mutant GluR (GluR2 L504Y) channel were expressed in HEK293 cells and investigated using the patch-clamp technique in combination with ultrafast agonist application. 3. When IEM-1460 was coapplied with glutamate, an open channel block mechanism was observed at slow desensitizing GluR2 flip (>/=0.1 mM IEM-1460) and nondesensitizing GluR2 L504Y channels (>/=1 microM IEM-1460). 4. A competitive block of AMPA-type channels was observed with IC(50) values for the dose block curves of 0.1 mM IEM-1460 at human unmutated and 10 microM IEM-1460 at mutant GluR channels. 5. Nondesensitizing GluR2 L504Y channels were used to further characterize the block mechanism. After equilibration with the agonist, a current decay upon coapplication of glutamate and IEM-1460 was observed. The recovery from block was independent of the glutamate and IEM-1460 concentration. The extent of current inhibition as well as the time constant of current decay upon addition of the blocker to the test solution were dependent on agonist concentration; this strongly points to an additional competitive-like block mechanism of IEM-1460 at human AMPA-type GluR channels. 6. The data were interpreted in the frame of a molecular scheme with two binding sites of IEM-1460 at the receptor, one at the unliganded resting and the other at the fully liganded open state of the channels.

Interaction of topiramate with glycine receptor channels.

Glycine receptor channels are pentameric ligand-gated ion channels that respond to the application of inhibitory neurotransmitters by opening of a chloride-selective central pore. Topiramate (TPM) is a broad-spectrum antiepileptic drug used as add-on or monotherapy for focal seizures. In the present study the interaction of TPM with glycine receptor channels was studied on outside-out patches from HEK293 cells expressing alpha1beta glycine receptor channels. The patch clamp techniques combined with ultra fast solution exchange enabled us to investigate the kinetics of receptor channels in presence of TPM. Our study showed no agonistic or potentiating effect for TPM on glycine receptor channels. However, in presence of 1 mM glycine + 1 mM TPM, the desensitization got faster and the peak current amplitude decreased. After the end of glycine + TPM pulses, off-currents occurred, suggestive for a specific channel block mechanism.

Effects of propofol on recombinant AMPA receptor channels.

The interaction of the anaesthetic propofol with recombinant human AMPA-type glutamate receptor channels was investigated by a patch-clamp study using fast agonist application techniques. Despite the marked effects of propofol on inhibitory synaptic transmission and voltage gated sodium channels, there is also evidence for a specific pharmacological action on AMPA receptors. In our study, we observed a deceleration of AMPA receptor channel desensitization in the prolonged presence of glutamate and propofol that is likely to account for the enhancement of ion currents through AMPA receptor channels observed in previous studies. While there was an increase in the rate and extent of desensitization at glutamate receptor 1, glutamate receptor 2, and glutamate receptor 3 AMPA receptors, no affection of current rise time, peak current amplitude, and deactivation properties was observed. Thus, our findings point to an isolated interaction with processes that control desensitization of AMPA receptor channels rather than indicating an interaction with channel opening and closing processes due to agonist binding and unbinding. The pharmacological effect described resembles in part that of compounds like cyclothiazide and aniracetam which are known to interact with channel desensitization.

Rat embryonic motoneurons in long-term co-culture with Schwann cells--a system to investigate motoneuron diseases on a cellular level in vitro.

Investigations of motoneuron diseases on a cellular and molecular level require long-term cultivation of primary cells. Here we present a new culture system in which matured motoneurons interact with their physiological partners like interneurons, astroglia and peripheral glia cells. This enables motoneuron-maturation for up to 3 weeks, while motoneurons consistently reached large diameters of their somata of 30-45 microm, occasionally more than 80 microm. Dissociated rat embryonic ventral spinal cord cells were enriched for motoneurons by density gradient centrifugation and seeded on a non-confluent mono-layer of highly enriched neonatal rat Schwann cells. Immunocytochemical visualization of neuron specific betaIII-tubulin in all neurons and of motoneuron specific non-phosphorylated neurofilament H/M, respectively, revealed that after 3 days in vitro >70% of all neurons were motoneurons. After 20 days in vitro, a motoneuron fraction of 12% was maintained. Motoneurons were susceptible to transient transfection with green fluorescent protein cDNA when liposomal transfection and an enhancer substance were combined. Synaptic connections enabled formation of spontaneously active neuronal networks which provide a culture model to study glutamate excitotoxicity and calcium deregulation on a molecular level. Both mechanisms are implied in the pathophysiology of amyotrophic lateral sclerosis, a neurodegenerative motoneuron disorder.

Desensitization and resensitization are independently regulated in human recombinant GluR subunit coassemblies.

AMPA-type glutamate receptor (GluR) channels are the most abundant excitatory transmitter receptors of the central nervous system. Four subunits with different posttranscriptional modifications and flip/flop splice variants are known. In vivo they occur as tetrameric heteromeric receptors. In the present study we analyzed the time course of desensitization (tau(D)) and resensitization (tau(rec)) kinetics of different homomeric (coassembly of splice or editing variants of one subunit) and heteromeric (coassembly of different subunits) GluR channels. We found that tau(D) had intermediate values depending on the amount of cDNA of the respective subunit at all heteromeric and homomeric GluR channels tested. The same holds true for tau(rec) except GluR2 flip channels were coexpressed with GluR1 channels. In this case, tau(rec) had values close to that of fast resensitizing GluR2 flip channels, even in the case of an abundance of GluR1 cDNA.

Amyotrophic lateral sclerosis: new developments in diagnostic markers.

There is an intensive search for diagnostic markers in amyotrophic lateral sclerosis (ALS). Protein analysis (proteomics) of the cerebrospinal fluid (CSF) appears particularly promising using mass spectrometry and 2-D gel electrophoresis to detect low and high molecular weight proteins, respectively. It is open whether protein changes specific for ALS will be found. This also holds true for inflammatory proteins such as the cytokine monocyte chemoattractant protein-1 which has been detected in CSF in ALS and for other cytokines such as interleukin-1beta. Increases of the protein Nogo A and B in muscle tissue and decreases of the growth factor vascular endothelial growth factor in blood may also be useful for monitoring the course of ALS. Clinical neurophysiology provides markers for upper and lower motor neuron damage. A very sensitive method to detect early upper motor neuron involvement is the transcranial magnetic stimulation modification 'triple stimulation technique' which can show significant changes in patients without clinical upper motor neuron signs. The loss of lower motor neurons can be closely monitored by MUNE techniques (motor unit number estimate). In modern imaging, the MRI technique DTI (diffusion tensor imaging) has the greatest diagnostic potential for ALS. It can separate between normal and ALS in group comparisons and may be improved to be diagnostic in individual patients. Voxel-based morphometry can reliably demonstrate regional cortical atrophy in motor areas and beyond although it is not appropriate for use in individual patients.