1. Department of Biochemistry and Human Physiology, University of Cagliari, Cittadella Universitaria, S. Prov.le Monserrato-Sestu Km 0.7, 09042 Monserrato (CA), Italy
2. CNR Center for Receptor Chemistry and Institute of Chemistry and Clinical Chemistry, Catholic University, Largo Francesco Vito 1, 00168 Roma, Italy