[Neurochemical early and differential diagnostics for Alzheimer's disease]. / Demenz-Fahndung im Labor. Die Liquoranalyse erkennt Alzheimer schon sehr früh.

Current medication procedures for Alzheimer's dementia (AD) such as inhibitors of acetyl cholinesterase or Memantine and future therapeutic approaches demand improved early diagnostics. However, the differentiation between early cognitive impairments due to primary progressive demential conditions and cognitive deficits in geriatric or depressive people is a great clinical challenge. The detection of biochemical markers such as beta-amyloid peptide and tau proteins in the cerebrospinal fluid can lead to improved diagnostics of the early stages and premonitory symptoms of AD. As a result, future preventive drug treatment strategies can be employed early and selectively.

Highly conserved and disease-specific patterns of carboxyterminally truncated Abeta peptides 1-37/38/39 in addition to 1-40/42 in Alzheimer's disease and in patients with chronic neuroinflammation.

Human lumbar CSF patterns of Abeta peptides were analysed by urea-based beta-amyloid sodium dodecyl sulphate polyacrylamide gel electrophoresis with western immunoblot (Abeta-SDS-PAGE/immunoblot). A highly conserved pattern of carboxyterminally truncated Abeta1-37/38/39 was found in addition to Abeta1-40 and Abeta1-42. Remarkably, Abeta1-38 was present at a higher concentration than Abeta1-42, being the second prominent Abeta peptide species in CSF. Patients with Alzheimer's disease (AD, n = 12) and patients with chronic inflammatory CNS disease (CID, n = 10) were differentiated by unique CSF Abeta peptide patterns from patients with other neuropsychiatric diseases (OND, n = 37). This became evident only when we investigated the amount of Abeta peptides relative to their total Abeta peptide concentration (Abeta1-x%, fractional Abeta peptide pattern), which may reflect disease-specific gamma-secretase activities. Remarkably, patients with AD and CID shared elevated Abeta1-38% values, whereas otherwise the patterns were distinct, allowing separation of AD from CID or OND patients without overlap. The presence of one or two ApoE epsilon4 alleles resulted in an overall reduction of CSF Abeta peptides, which was pronounced for Abeta1-42. The severity of dementia was significantly correlated to the fractional Abeta peptide pattern but not to the absolute Abeta peptide concentrations.

[Neuronal potassium channel opening with flupirtine]. / Neuronale Kaliumkanalöffnung durch Flupirtin.

The spectrum of action of flupirtine includes analgesic, muscle-relaxant and neuroprotective properties. The substance's mechanism of action has yet to be fully explained. Over the past few years, however, evidence has accumulated that flupirtine interacts with the glutamatergic N-Methyl-D-Aspartate (NMDA) receptor. Although it was not possible to demonstrate a direct effect on the NMDA receptor, all of the findings pointed to an indirect influence on the NMDA receptor in the sense of a functional NMDA antagonism. It was thus postulated that a site of action "up- or downstream" of the NMDA receptor is influenced. Such a site of action proved to be the G-protein-activated inwardly rectifying K+ channels (GIRK), the opening of which leads to a stabilization of the resting membrane potential of neuronal cells and thus causes an indirect inhibition of the NMDA receptor. At therapeutically relevant concentrations, flupirtine is a neuronal potassium channel opener. This mechanism may explain the spectrum of action of flupirtine. Selective neuronal potassium channel opening (SNEPCO) thus proves to be a new principle of action, making flupirtine the prototype of a new substance class with analgesic, muscle-relaxant and neuroprotective properties. The experimental basis for this working hypothesis and the resulting model concepts are presented from the perspective of a four-stage approach.

Flupirtine shows functional NMDA receptor antagonism by enhancing Mg2+ block via activation of voltage independent potassium channels. Rapid communication.

The spectrum of action of flupirtine includes analgesia, muscle relaxation and neuroprotection. N-methyl-D-aspartate (NMDA) receptor antagonism has been discussed as a possible mechanism of action of this compound with little direct evidence. The objective of the present study was to develop a plausible model to explain flupirtine's spectrum of action. A four-stage strategy was selected for this purpose: Firstly, the serum concentration of flupirtine under therapeutic conditions was determined on the basis of the current literature. The second stage involved assessing the known in-vitro effects in light of the therapeutic active concentration. Using whole cell patch clamp recordings from cultured rat superior colliculus neurones interactions between flupirtine and NMDA receptors were assessed. Only very high concentrations of flupirtine antagonized inward currents to NMDA (200 microM) at -70 mV with an lC50 against steady-state responses of 182.1+/-12.1 microM. The effects of flupirtine were voltage-independent and not associated with receptor desensitization making actions within the NMDA receptor channel or at the glycine modulatory site unlikely. NMDA receptor antagonism probably has little relevance for the clinical efficacy of flupirtine as the concentrations needed were far higher than those achieved in clinical practice. However, the activation of a G-protein-regulated inwardly rectifying K+ channel was identified as an interesting molecular target site of flupirtine. In the next stage, the central nervous spectrum of action of experimental K+ channel openers (PCO) was considered. As far as they have been studied, experimental K+ channel openers display a spectrum of action comparable to that of flupirtine. In the final stage, a global model was developed in which flupirtine stabilizes the resting membrane potential by activating inwardly rectifying K+ channels, thus indirectly inhibiting the activation of NMDA receptors. The model presented here reconciles the known functional NMDA receptor antagonism of flupirtine with the activation of K+ channels that occurs at therapeutic concentrations, thus providing an understanding of flupirtine's spectrum of action. This makes flupirtine the prototype of a clinically applicable substance group with analgesic, muscle-relaxant and neuroprotective properties.

High-dose delay of the immune response. Effect of actinomycin D on continuation of the immune response in vitro.

The continuation of the primary and secondary antibody response to human serum albumin (HSA), induced in vivo, was followed in explanted chicken spleen fragments. The effect of actinomycin D (AMD) on the in vitro response was studied in spleens from chickens injected with various doses of HSA and removed at differing intervals after injection. The antibody response of "early spleen" cultures was AMD-sensitive, while cultures of spleens removed later were AMD-resistant. It was suggested that this shift represented the development of cells with in vivo preformed RNA involved in specific immunoglobulin synthesis. With increasing doses of HSA, the AMD-sensitive phase was prolonged, suggesting the delay of mRNA formation or some other AMD-inhibitable process in vivo. With large doses of HSA, the immune response in vitro was decreased, starting after a 1-2 day delay and not occurring in the presence of AMD. Massive doses of HSA completely inhibited the continuation of the response in vitro by spleen fragments removed between the 2nd and 5th day after injection. The results point to the controlling role of antigen dose in determining the onset of macromolecular synthesis during immunocyte maturation.