1. Neurobiological Research Laboratories, Fidia Research Laboratories; Via Ponte delia Fabbrica 3/a 35031 Abano Terme Italy
2. Institute of Human Physiology; University of Modena; Via Campi, 287 41100 Modena Italy
3. Institute of Histology; Karolinska Institutet.; P.O.B. 60400 S-104 01 Stockholm Sweden