[Polymorphism of brain derived neurotrophic factor and recovery of functions after ischemic stroke]. / Polymorphismus des "brain derived neurotrophic factor" und Erholung nach Schlaganfall.

BACKGROUND: After ischemic stroke, many factors influence the restitution of functions. In particular they include the patient age, the initial stroke severity and the presence of cognitive and neuropsychological deficits. In this study we investigated whether a polymorphism in the gene encoding for brain derived neurotrophic factor (BDNF) influences improvements of motor functions and everyday activities. METHODS: Patients with subacute ischemic stroke (n = 67) were examined at the beginning of an inpatient neurological rehabilitation, after 4 weeks of treatment and after 6 months. The Barthel index (BI) and the Rivermead motor assessment (RMA) were used to measure motor functions and everyday activities. Patients were allocated to three groups (valine [Val]/valine, val/methionine [Met] and Met/Met) depending on the BDNF polymorphism at codon 66. RESULTS: The 3 groups (Val/Val, n = 34 patients, Val/Met, n = 26 and Met/Met, n = 7) showed significant improvements in BI and RMA after 4 weeks and after 6 months as compared to the preceding measurements. The BI and RMA were positively correlated. The three groups did not differ with respect to the extent of improvement. CONCLUSION: After ischemic stroke, motor functions and everyday activities improved continuously over a period of at least 6 months. The BDNF polymorphism did not influence this development.

Prefrontal dopamine and the dynamic control of human long-term memory.

Dopaminergic projections to the prefrontal cortex support higher-order cognitive functions, and are critically involved in many psychiatric disorders that involve memory deficits, including schizophrenia. The role of prefrontal dopamine in long-term memory, however, is still unclear. We used an imaging genetics approach to examine the hypothesis that dopamine availability in the prefrontal cortex selectively affects the ability to suppress interfering memories. Human participants were scanned via functional magnetic resonance imaging while practicing retrieval of previously studied target information in the face of interference from previously studied non-target information. This retrieval practice (RP) rendered the non-target information less retrievable on a later final test-a phenomenon known as retrieval-induced forgetting (RIF). In total, 54 participants were genotyped for the catechol-O-methyltransferase (COMT) Val(108/158)Met polymorphism. The COMT Val(108/158)Met genotype showed a selective and linear gene-dose effect on RIF, with the Met allele, which leads to higher prefrontal dopamine availability, being associated with greater RIF. Mirroring the behavioral pattern, the functional magnetic resonance imaging data revealed that Met allele carriers, compared with Val allele carriers, showed a greater response reduction in inhibitory control areas of the right inferior frontal cortex during RP, suggesting that they more efficiently reduced interference. These data support the hypothesis that the cortical dopaminergic system is centrally involved in the dynamic control of human long-term memory, supporting efficient remembering via the adaptive suppression of interfering memories.

Semi-automated analysis of NMDA-mediated toxicity in digitised colour images from rat hippocampus.

The evaluation of neuronal cell survival after, for example, mechanical, hypoxic or drug-mediated injury requires the analysis of a high number of histological specimens. Since this is a time-consuming occupation, we have developed a semi-automated analysis routine for the determination of the distribution of live and dead cells. After digitalization of the histological preparations, 8-bit colour bitmaps were assessed using a compiled image-analysis programme of the software package Khoros. In the current study a detailed example of the application of this image-processing approach is described for the investigation of the cell survival after intraventricular application of N-methyl-D-aspartate (NMDA). The samples were prepared as fuchsin acid/toluidine blue stained hippocampal thin slices. The calculated areas of the live and dead cells were highly correlated with manual counts of live and dead cells in the 100 samples examined in this study. Twenty-four hours following NMDA-treatment animals (n = 5) were found to have significantly fewer live and more dead hippocampal cells than the saline-treated animals (n = 5), using either automated or manual examination techniques. The automated technique also revealed that NMDA treatment resulted in a reduction in the density of live cell distribution.