MAO inhibitory side effects of neuroleptics and platelet serotonin content in schizophrenic patients.

In order to study the putative monoamine oxidase (MAO) inhibitory side effect of neuroleptics and simultaneous changes in platelet serotonin content both MAO-B activity and serotonin (5-HT) content in platelets of 30 healthy volunteers and 50 schizophrenic patients treated with neuroleptics were investigated. Our results have shown significantly lower MAO-B activity (15.26 +/- 6.81 S.D. vs. 8.63 +/- 3.82 mmol/hour/10(9) platelets) and higher platelet 5-HT content (906.19 +/- 285.33 vs. 1,727.85 +/- 947.40 ng/10(9) platelets) in the schizophrenic group. Platelet MAO-B activity was considerably lower in paranoid and residual schizophrenics compared with other patients, however, no difference was found in platelet 5-HT content between different subtypes of schizophrenia. Various neuroleptic treatments did not produce different effects either on platelet serotonin content or platelet MAO-B activity.

Platelet MAO-B activity and serotonin content in patients with dementia: effect of age, medication, and disease.

This study aimed at determining the effect of drug therapy, age and type of dementia on biological markers. Both platelet monoamine oxidase type B (MAO-B) activity and serotonin content of 57 demented patients and 20 control subjects were determined. Platelet MAO-B activity was measured using [14C]tyramine as substrate. Serotonin content was determined by HPLC-EC method. Increased platelet serotonin content and platelet count was found in patients with dementia compared to controls. A positive correlation was experienced between platelet MAO-B activity, platelet serotonin content and age. Platelet MAO-B activity was higher in the haloperidol treated group, compared with patients treated with anxyolitics. The main original finding of the present study is that platelet serotonin content is increased in demented patients with delusions compared to dementia without complications (p = 0.006). It seems, that platelet MAO-B activity is influenced mainly by drug therapy, while serotonin content rather reflects clinical characteristics in dementia.

Platelet rich plasma serotonin content in patients suffering from different psychiatric disorders.

Platelet rich plasma serotonin contents were examined using HPLC-EC method in patients suffering from different anxiety states and compared to age matched healthy controls. We have found significant increase of PRP serotonin level in the group of schizophrenic patients and in patients suffering from dementia compared to controls. PRP serotonin content was significantly lower in heavy drinkers but in patients suffering from panic disorder did not differ significantly from the controls.

Local depletion of monoamines induced with in vivo voltammetry in the cat brain.

A significant depletion of the electroactive monoamines and their metabolites in the vicinity of a carbon fiber microelectrode may be induced by in vivo staircase voltammetry in the brain, even if the duration of the voltammetric scans is relatively short (approximately 5 s). The variation of this depletion was determined in the extracellular fluid of the cat thalamus at different durations of the pauses separating consecutive measurements. Pauses not shorter than 5 min ensured a nearly full relaxation, so that at the beginning of each subsequent scan a virtually undisturbed environment surrounded the electrode. With pauses shorter than 5 min, it is still possible to monitor major changes in the monoamine concentration. Staircase scans separated with 45 s pauses, for example, were suitable to study the increase in monoamine levels after administration of reserpine, and release phenomena stimulated with KCl were monitored with frequently repeated voltammetric pulses. The electrochemically induced depletion, on the other hand, can be used for characterizing the dynamics of mass transport in the studied brain structure. This was demonstrated with staircase voltammetry alternated with pauses of 1-100 s, and with quasi-chronoamperometry. In vivo brain voltammetry is generally used for monitoring extracellular monoamine (including dopamine) levels. These may be significantly altered by the voltammetric measurement itself through depletion in the vicinity of the electrode. This effect can be minimized with appropriate selection of sampling intervals and other parameters of staircase voltammetry. Conversely, depletion and the following relaxation can be used for determining dynamic characteristics of the studied brain structure which would be difficult to obtain otherwise.

Electrochemical calibration of in vivo brain dialysis samplers.

Measurement of state-related changes in the concentration of an endogenous substance using the in vivo dialysis technique requires a definition of the factors which relate the concentration detected in the outflowing perfusate to the concentration actually occurring in the extracellular space in which the sampler is located. In determine these factors, a rapid and highly accurate detector system is required which measures the concentration recovery in the perfusate and the dead space of the entire sampling system. To reduce the limitations of the microdialysis technique, two electrochemical microcells were developed for calibration of dialysis probes by computerized voltammetry. The electrochemically calibrated samplers were implanted into freely moving cats to measure concentration changes of monoamine metabolites in synchrony with sleep stages identified by polygraphy in order to demonstrate the applicability of electrochemical calibration in dialysis methods used in behavioral investigations.