Prof. Dr. Irmgard Dietzel-Meyer, Molecular Neurochemistry, Faculty of Chemistry and Biochemistry
Neurons respond to stimuli with cell-type specific firing patterns, governed by characteristic distributions of voltage-activated ion channels. One of our research goals is to elucidate to what extent the firing pattern of a cell can still be modulated by external factors after the developmental decision to a particular neural subtype has been made. As an example of clinical relevance we have found that deficiency of thyroid hormone in the postnatal period, which causes irreversible mental retardation, induces a downregulation of voltage-activated Na+- currents in hippocampal (Potthoff and Dietzel, 1997) and cortical neurons, concomitant with a decrease in action potential upstroke velocity and firing frequency (Hoffmann and Dietzel, 2004). We are presently elucidating the molecular mechanisms by which thyroid hormone affects Na+- current regulation in neurons (Niederkinkhaus et al., 2007) as well as the regulation of Na+/K+-ATPases and the mechanisms responsible for the different effects of thyroid hormone on postnatal and mature brain.
To study effects of the molecular environment on the shapes of single living cells we have developed a scanning ion condutance microscope (SICM), which can presently monitor cell volume and local membrane surface changes with a resolution of less than 500 nm (Happel et al., 2003; Mann et al., 2006). We have recently applied this method to characterize influences of cytotoxic cytokines on oligodendrocyte precursor cell maturation (Mann et al., 2007). Since survival and differentiation of oligodendrocyte precursors can be compromised by perinatal infections thus leading to motor impairments we are currently studying the molecular mechanisms of cell damage, mostly concerning changes in ion currents, and possible strategies for protection of these myelin forming cells in the central nervous system.