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.

[Orofaciodigital syndrome--a new variant? Psychiatric, neurologic and neuroradiological findings]

Oral-facial-digital (OFD) syndromes are a heterogeneous group of inherited syndromes that have in common anomalies of the face (median cleft lip), the tongue (bifid or lobulated tongue with harmartomas), and the digits (brachydactyly, polydactyly, syndactyly). Due to more or less subtle clinical features, at least seven causally different entities can be identified: 1) OFDS I; 2) OFDS II (Mohr syndrome); 3) OFDS III; 4) OFDS with tibial anomalies (OFDS IV); 5) OFDS V (Thurston syndrome); 6) OFDS VI (Váradi syndrome); and 7) OFDS VII (Whelan syndrome). The neuro-psychiatric clinical observations and MRI findings of a 40 year old woman with a OFD syndrome are described. The observed findings (leukoaraiosis, epilepsy, major depression) in combination with a proven OFD syndrome possibly reflect a new type of OFD syndrome.

[Neuronal potassium channel opening with flupirtine]

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.

[Death caused by stomach rupture due to overinflation during oxygen administration via stomach tube]

Soon after transfer from an intensive care unit to a normal ward within a hospital a 59-year-old female patient died. The investigation revealed that oxygen was insufflated accidentally through a nasogastric tube into the stomach and the intestinum. Autopsy showed a distended abdomen and odorless free gas streaming out of the opened abdomen. In the gastric wall, a 12 cm long rupture and 5 more incomplete ruptures were found. A most possible mechanism of gastric rupture due to overstretching by insufflated gas is presented. Criminal responsibility was excluded as the cause of the death could not be stated without reasonable doubt. The problem of selecting patients for intensive care to the disadvantage of others who also might profit from this special treatment is discussed.

[Drowning by aspiration of oral saline administration]

A fatal case of salt water ingestion of a 35-year old drug addict is presented. Resuscitation by emergency doctor after first-aid was not successful. Autopsy revealed the classical signs of drowning. In the sphenoid sinus sodium-chloride could be detected. The diagnosis and differential diagnosis of drowning is discussed.