1. Peptide Neurochemistry, LCBRA, National Institute of Environmental Health Sciences, P.O. Box 12233, Mail Drop C3-04, Research Triangle Park, North Carolina 27709, Naval Research Laboratory, Washington, D.C., Faculty of Pharmaceutical Science and Biotechnology Center, University of Ferrara, I-44100 Ferrara, Italy, and Department of Toxicology, University of Cagliary, I09126 Cagliary, Italy