1. From Institute of Physiology (R.S., U.K., G.L.), University Rostock, Germany; Institute of Physiology (I.W., D.S., J.R.S.), University Hamburg, Germany; Institute of Anatomy (N.U.), RG Neuroembryology, University Rostock, Germany; Institute of Anatomy (R.W.V.), Charite, Humboldt-University, Berlin, Germany; Institute of Biophysics (H.G.), Bulgarian Academy of Sciences, Sofia, Bulgaria.