[Glutamate--a transmitter in the tensionfield between toxin and trophine]

Glutamate is the most important excitatory transmitter in the central nervous system. A tremendous complexity in the actions of this excitatory transmitter was found and an equally great complexity in the molecular structures of the receptors activated by glutamate. The glutamate receptor system influences nearly all other neurotransmitter systems. Glutamate also plays a central role in important processes of the central nervous system like the long-term potentiation in the hippocampus and the central sensitization for pain stimuli in the spinal cord, which is predominantly mediated by NMDA-receptors. But there are actions of glutamate beyond its function as an excitatory transmitter. Glutamate also has a trophic influence on neurons--depending upon the developmental stage. The excitotoxicity of glutamate mediated by NMDA-receptors is the common ultimate mechanism of acute and chronic nerve cell death and plays an important role in many acute neurologic diseases. The modulation of the glutamate system for example by antagonist of the glutamate-receptors might be a possible way in therapy of many different diseases of the central nervous system.

[Excitatory neurotransmission in alcoholism]

Glutamate is the neurotransmitter at the majority of excitatory synapses in the mammalian CNS. It has been proposed that neurotoxicity linked to chronic alcoholism is mediated primarily by activation of glutamate N-methyl-D-aspartate (NMDA) receptors. Since ethanol stabilizes the membrane potential of NMDA receptors a persistent attenuation of glutamatergic neurotransmission occurs in chronic alcoholism resulting in a compensatory up-regulation of NMDA receptors. Thus, delayed neurotoxicity can be triggered by rebound activation of NMDA receptor-mediated neurotransmission during the withdrawal state. Besides glutamate, homocysteine and excitatory amino acids (EAA) have been shown to act as endogenous agonists at the NMDA receptor and increase excitatory postsynaptic potentials. There is evidence that chronic alcoholism is associated with a derangement in this sulfur amino acid metabolism. These findings indicate the role of hyperhomocysteinemia for withdrawal symptoms, the withdrawal state, and alcoholism-associated brain atrophy. The role of alcoholism-associated hyperhomocysteinemia in respect to NMDA-receptor mediated neurotoxicity and excitotoxicity is discussed.

Apolipoprotein E epsilon 4 is associated with hippocampal volume reduction in females with alcoholism

There is evidence that a higher incidence of diverse neurodegenerative diseases is associated with the apolipoprotein E epsilon4 allele (ApoE4). Most recently it has been found that the ApoE4 allele is specifically related to an accelerated hippocampal atrophy in patients with Alzheimer's disease. Therefore, the aim of the present study was to investigate the association between ApoE4 genotypes and brain hippocampal volume reduction in alcoholics by using volumetric high-resolution MR imaging. In the present study, female alcoholics with the ApoE4 genotype were found to have significantly smaller hippocampal volumes than those not carrying an epsilon4 allele (ANOVA, p < 0.05), whereas no differences in hippocampal volume were seen in male alcoholics. Since hippocampal volume reduction is lately discussed to be proportional to brain atrophy, we propose that the alcohol-related brain atrophy in patients suffering from chronic alcoholism, is more pronounced in female carriers of the apoE epsilon4 allele. These findings indicate a genetic disposition for alcohol related brain atrophy in female carrying the ApoE4 genotype, which may also explain why female alcoholics are more susceptible to alcohol-induced brain damage.

[Homocysteine and dementia]

Homocysteine is a vascular risk factor including cerebral macroangiopathy and microangiopathy. Furthermore, there might also be an association with cognitive disorders including vascular dementia and Alzheimer's disease. Hyperhomocysteinemia linked with cognitive impairment might be an indirect marker for low concentrations of vitamin B 12, vitamin B 6 or folate, resulting from low intake or from an impaired transport of the vitamins to the brain. Another possibility is a direct harmful effect of homocysteine to cognition via vascular and neurotoxic pathophysiologic mechanisms. Because hyperhomocysteinemia is a potentially reversible risk factor and can be identified early, it should be investigated by prospective intervention studies whether lowering homocysteine levels by vitamin supplementation could reduce incidence and progression of cognitive disorders.

Hyperhomocysteinemia as a new risk factor for brain shrinkage in patients with alcoholism

Chronic alcohol consumption can induce brain atrophy, whereby the exact mechanism of brain damage in alcoholics remains unknown. There is evidence that chronic alcoholism is associated with hyperhomocysteinemia. Homocysteine is an excitatory amino acid which markedly enhances the vulnerability of neuronal cells to excitotoxic and oxidative injury in vitro and in vivo. The present volumetric magnetic resonance imaging study included 52 chronic alcoholics and 30 non-drinking healthy controls. Patients were active drinkers and had an established diagnosis of alcohol dependence. We investigated the influence of different variables on the hippocampal volume of patients suffering from chronic alcoholism. We observed that pathological raised levels of plasma homocysteine showed the most significant correlation to hippocampal volume reduction (P<0.001, multiple regression analysis). Raised plasma levels of homocysteine are associated with hippocampal (brain) atrophy in alcoholism.

Lack of association between hippocampal volume reduction and first-onset alcohol withdrawal seizure. A volumetric MRI study

AIMS AND METHODS

Magnetic resonance imaging (MRI) of the hippocampus has been extensively studied in both neurological and psychiatric disorders. Furthermore, hippocampal volume reductions on MRI have been reported in patients with chronic alcoholism. The present volumetric MRI study was undertaken to determine whether an association exists between hippocampal volume reduction and first-onset alcohol withdrawal seizure. Until recently, no data as to whether hippocampal volume reductions in alcoholics might serve as a predictor of withdrawal seizures were available.

RESULTS

We found the average hippocampal volumes measured by high resolution MRI to be significantly reduced in 52 alcoholics compared with 30 healthy controls. Besides a decrease of hippocampal volume in patients with chronic alcoholism, we could not find any significant correlation between the occurrence of seizures during alcohol withdrawal and the amount of hippocampal volume reduction in these patients.

CONCLUSIONS

Thus, the alcoholism-related atrophy within the hippocampal formation in patients suffering from chronic alcoholism does not seem to be the source of convulsive activity in these patients. Neither does the amount of atrophy allow the occurrence of first-onset withdrawal seizures to be predicted.

Homocysteine and risk of open-angle glaucoma

Homocysteine levels and the frequency of heterozygous methylenetetrahydrofolate reductase (MTHFR) C677T mutation are increased in open-angle glaucoma. Since homocysteine can induce vascular injury, alterations in extracellular matrix remodelling, and neuronal cell death, these findings may have important implications for understanding glaucomatous optic neuropathy.

Spontaneous, slow and fast magnetoencephalographic activity in patients with schizophrenia

A 2* 37 channel biomagnetic system (Magnes II) was used to record spontaneous magnetic activity for the frequency ranges 2-6 Hz and 12.5-30 Hz in 30 patients with schizophrenia (23 men and 17 women) and 30 healthy volunteers in both hemispheres during a resting condition. The dipole localization was calculated by the dipole density plot (DDP) method, which is a spatial averaging in order to decrease the influence of the nonfocal activity. The quantified DDP results were superimposed to T2-weighted MR-images of each patient's head as isocontour lines. To superimpose the MEG results to 3-D MRI data, the scanned head data set was fitted to the reconstructed MRI head shape using a surface fit programme developed by our department. The absolute dipole values were correlated with the psychopathological findings and the cumulative neuroleptic dosage for each patient. The group of patients with schizophrenia differed overall from the healthy subjects in the elevation of absolute dipole values measured in both hemispheres. For the region of slow dipole activity (2-6 Hz), a high correlation was found between the intensity of dipole concentration and productive psychotic symptoms (PANSS, P1-P7). Dipole localization (for both frequency ranges) showed a concentration effect (DCE) in the temporoparietal region in patients with schizophrenia.

Separation anxiety and actual separation experiences during childhood in patients with panic disorder

OBJECTIVE

The association between separation anxiety in childhood and actual separation experiences during childhood has not yet been investigated in patients with panic disorder.

METHODS

In 115 patients with panic disorder with or without agoraphobia and in 124 control subjects without a history of psychiatric illness, we assessed separation anxiety during childhood, retrospectively, using DSM-IV and ICD-10 criteria and the Separation Anxiety Symptom Inventory (SASI). In addition, actual separation experiences from age 0 to 15 years were assessed, retrospectively.

RESULTS

A total of 22.6% of the patients and 4.8% of the control subjects fulfilled both DSM-IV and ICD-10 criteria for childhood separation anxiety (chi 2 = 11.8; P < 0.0001). Further, 57.4% of the patients and 37.9% of the control subjects reported actual separation experiences during their childhood (chi 2 = 9.09, P < 0.003). Separation anxiety and actual separation experiences, however, were independent of each other.

CONCLUSION

These results suggest that separation anxiety during childhood is not a consequence of actual traumatic separation experiences in panic disorder patients.

Clozapine-associated elevation of plasma cholinesterase

OBJECTIVE

The goal of this study was to identify adverse effects of the atypical neuroleptic clozapine on liver function and lipid metabolism.

METHODS

Data which included serum levels of clozapine and its hepatic metabolite N-desmethyl clozapine were collected from medical records of patients treated with clozapine and controls.

RESULTS

We identified a clozapine-associated marked elevation of plasma cholinesterase (ChE) with unchanged levels of AST, ALT or g-GT. ChE was correlated to the serum level of clozapine and even closer to N-desmethyl clozapine. For the total patient group we observed significant correlations of ChE with the body-mass index and body weight. However, clozapine-treated patients and controls did not differ with regard to body-mass index, triglycerides, and cholesterol.

CONCLUSION

We report for the first time a clozapine-associated and dose-dependent elevation of plasma ChE, which may be related to clozapine-associated effects on hepatic lipid metabolism or ChE enzyme induction.

[Glutamatergic neurotransmission in schizophrenics]

Glutamate is the most abundant amino acid in the brain, where it plays an important role as a well-established major excitatory neurotransmitter in the central nervous system. It has been suggested that reduced glutamate neurotransmission may be involved in the pathophysiology of schizophrenia. The glutamate hypothesis of schizophrenia postulates alterations in the glutamatergic system as an important neurobiochemical event in the pathophysiology of this group of psychotic disorders. An altered glutamate release from synaptosomes including a hypofunction of different glutamate receptors (i.e. NMDA receptors) from different brain areas have previously been reported. Furthermore, partial agonists at the glycine co-agonist site of the NMDA receptor might be a new approach in the treatment of schizophrenic symptoms but further studies are necessary to clarify the role and efficacy of these substances in schizophrenia. Changes in the glutamatergic cortico-striatal connections in schizophrenia could precipitate a potential perceptive overstimulation of the neocortex from thalamic input and an inhibiting influence of the striatum on the thalamus would modulate the information input of the cortex, thereby possibly counteracting the disturbed information processing which is relatively characteristic for schizophrenic psychoses.

Moderate alcohol consumption in social drinkers raises plasma homocysteine levels: a contradiction to the 'French Paradox'?

Evidence from observational studies suggests that elevated levels of homocysteine are associated with an increased risk of cardiovascular diseases. We assessed whether moderate alcohol intake in healthy social drinkers, suggested to be cardioprotective according to the 'French paradox', influences the cardiovascular risk factor homocysteine. A total of 60 normal nourished subjects who had no evidence of vascular disease or other risk factors for hyperhomocysteinaemia were assigned to receive mineral water or 30 g of alcohol per day (as beer, red wine or spirits) for a period of 6 weeks. Homocysteine levels of social drinkers, independent of which beverage was consumed, increased during the observation. We postulate that elevated levels of homocysteine in social drinkers with regular moderate alcohol intake are at risk of developing cardiovascular diseases, which contradicts the suggested cardioprotection of alcohol according to the 'French paradox'.

Fixation-off sensitivity in an adult with symptomatic occipital epilepsy

An adult patient had EEG occipital spike fixation-off sensitivity and spontaneous occipital seizures due to perinatal asphyxia with bioccipital hemorrhage. EEG abnormalities consisted of repetitive posterior spikes that occurred when the eyes were closed and other conditions of fixation-off. Magnetic resonance imaging (MRI) documented severe posterior lesions with wallerian degeneration of the optic radiation. Electron capture detector single-photon emission computed tomography (ECD-SPECT) during the state of fixation-off showed regional hyperperfusion in the right posterior regions. We suggest that partial denervation of the primary visual cortex in this patient resulted in an increased cortical excitability and that the inhibitory effect of central vision and fixation leads to a suppression of spontaneous epileptic activity. This unusual symptomatic case may serve as a model for the pathophysiology in the more often reported cases of idiopathic benign epilepsy syndrome of childhood.

Risk assessment of alcohol withdrawal seizures with a Kohonen feature map

Recently, it has been suggested that alcohol-induced hyperhomocysteinaemia in patients suffering from chronic alcoholism might be a risk factor for alcohol withdrawal seizures. In the present follow-up study 12 patients with chronic alcoholism who suffered from withdrawal seizures had significantly higher levels of homocysteine (Hcy) on admission (71.43 +/- 25.84 mol/l) than patients (n = 37) who did not develop seizures (32.60 +/- 24.87 mol/l; U = 37.50, p = 0.0003). Using a logistic regression analysis, withdrawal seizures were best predicted by a high Hcy level on admission (p < 0.01; odds ratio 2.07). Based on these findings we developed an artificial neural network system (Kohonen feature map, KFM) for an improved prediction of the risk of alcohol withdrawal seizures. Forty-nine patients with chronic alcoholism (12 with alcohol withdrawal seizures and 37 without seizures) were randomized into a training set and a test set. Best results for sensitivity of the KFM was 83.3% (five of six seizure patients were predicted correctly) with a specificity of 94.4% (one false positive prediction of 19 patients). We conclude that in patients with alcohol-induced hyperhomocysteinaemia the KFM is a useful tool to predict alcohol withdrawal seizures.

Homocysteine and alcoholism

Chronic alcohol consumption can induce alterations in the function and morphology of most if not all brain systems and structures. However, the exact mechanism of brain damage in alcoholics remains unknown. Partial recovery of brain function with abstinence suggests that a proportion of the deficits must be functional in origin (i.e. plastic changes of nerve cells) while neuronal loss from selected brain regions indicates permanent and irreversible damage. There is growing evidence that chronic alcoholism is associated with a derangement in the sulfur amino acid metabolism. Recently, it has been shown that excitatory amino acid (EAA) neurotransmitters and homocysteine levels are elevated in patients who underwent withdrawal from alcohol. Furthermore, it has been found that homocysteine induces neuronal cell damage by stimulating NMDA receptors as well as by producing free radicals. Homocysteine neurotoxicity via overstimulation of N-methyl-D-aspartate receptors may contribute to the pathogenesis of both brain shrinkage and withdrawal seizures linked to alcoholism.

Molecular biology of Alzheimer's dementia and its clinical relevance to early diagnosis and new therapeutic strategies

Over the past few years, molecular biological research has considerably deepened our understanding of the pathophysiological basis of Alzheimer's dementia (AD). Although different genetic origins of the disease have been identified, all of the findings point to a common terminal sequence in familial AD. This consists of an increased production of beta-amyloid peptides from beta-amyloid precursor protein. For the cases of sporadic AD, which far outweigh the number of cases of familial AD, an impaired catabolism of the beta-amyloid peptides may also be pathophysiologically decisive according to the latest findings. Research into the molecular level of AD makes it possible to identify points of attack for rational drug treatment of the disease, while molecular markers of AD are increasingly being used as a part of early and differential neurochemical diagnostics.

[New antidepressant drugs. What side effects and interactions are to be expected?]

The new antidepressants, selective serotonin reuptake inhibitors (SSRI), selective serotonin noradrenalin reuptake inhibitors (SSNRI) and selective noradrenalin reuptake inhibitors (SNRI) have few clinically relevant side effects. Overall, the new antidepressants are better tolerated and cause fewer side effects than the classical tricyclic antidepressants (TCA). They have virtually no anticholinergic effects, a low level of toxicity, and produce no psychomotoric or cognitive impairment. Both the frequency and severity of gastrointestinal and CNS side effects, as well as tremor, are low. The results of the drug safety program (AMSP) confirm the good tolerability and low clinical side effects of these new substances.