1 Department of Biochemistry and Molecular Biology, Faculty of Chemical Sciences, University of Salamanca, 37007 Salamanca, Spain.
2 Group GIR-BMD (Bases Moleculares del Desarrollo), University of Salamanca, 37007 Salamanca, Spain.
3 Laboratory of Neuroanatomy of the Peptidergic Systems, Institute of Neurosciences of Castilla y León (INCYL), University of Salamanca, 37007 Salamanca, Spain.