Jan Loock

Functional screening of traditional antidepressants with primary cortical neuronal networks grown on multielectrode neurochips

We optimized the novel technique of multielectrode neurochip recordings for the rapid and efficient screening of neuroactivity. Changes in the spontaneous activity of cultured networks of primary cortical neurons were quantified to evaluate the action of drugs on the firing dynamics of complex network activity. The multiparametric assessment of electrical activity changes caused by psychoactive herbal extracts from Hypericum, Passiflora and Valeriana, and various combinations thereof revealed a receptor‐specific and concentration‐dependent inhibition of the firing patterns. The spike and burst rates showed significant substance‐dependent effects and significant differences in potency. The effects of specific receptor blockades on the inhibitory responses provided evidence that the herbal extracts act on gamma‐amino butyric acid (GABA) and serotonin (5‐HT) receptors, which are recognized targets of pharmacological antidepressant treatment. A biphasic effect, serotonergic stimulation of activity at low concentrations that is overridden by GABAergic inhibition at higher concentrations, is apparent with Hypericum alone and the triple combination of the extracts. The more potent neuroactivity of the triple combination compared to Hypericum alone and the additive effect of Passiflora and Valeriana suggest a synergy between constituent herbal extracts. The extracts and their combinations affected the set of derived activity parameters in a concomitant manner suggesting that all three constituent extracts and their combinations have largely similar modes of action. This study also demonstrates the sensitivity, selectivity and robustness of neurochip recordings for high content screening of complex mixtures of neuroactive substances and for providing multiparametric information on neuronal activity changes to assess the therapeutic potential of psychoactive substances.

Improvement of impaired albumin binding capacity in acute‐on‐chronic liver failure by albumin dialysis

Extracorporeal albumin dialysis (ECAD) enables the elimination of albumin bound substances and is used as artificial liver support system. Albumin binding function for the benzodiazepine binding site specific marker Dansylsarcosine was estimated in plasma samples of 22 patients with cirrhosis and hyperbilirubinaemia (ECAD: n = 12; control: n = 10) during a period of 30 days in a randomized controlled clinical ECAD trial. Albumin Binding Capacity (ABiC) at baseline was reduced to 31.8% (median; range 24%‐74%) and correlated to the severity of liver disease. Within two weeks a significant improvement of ABiC and a reduction of the albumin bound markers bilirubin and bile acids were observed in the ECAD group. During single treatments a significant decrease of albumin bound substances (bilirubin and bile acids) as well as an increase in ABiC was observed. In the control group, baseline ABiC was significantly lower in patients who died during study period (34.2% vs. 41.7%; P < 0.028), whereas no significant differences were observed for CHILD, coagulation factors, albumin, bile acids nor bilirubin. At baseline 13 patients had a severely impaired ABiC (<40%), improvement of ABiC was more frequent in the ECAD group (5/6) than in the SMT group (2/7). Reduced albumin binding function is present in decompensated liver failure and is related to severity and 30 day survival. ABiC can be improved by ECAD. The beneficial effect of this treatment may be related to the improvement of albumin binding function more than to the elimination of specific substances. Characterization of albumin function by the ABiC test may help to evaluate different liver support systems and other therapeutic measures. Liver Transpl 14:1333–1339,2008.