1. Behavioral Genetics Laboratory; Department of Biobehavioral Sciences; The University of Connecticut; Storrs CT 06268 U.S.A.
2. Department of Psychiatry; School of Medicine; Southern Illinois University; Springfield IL 62708 U.S.A.
3. Istituto di Farmacologia, IV Cattedra; Facolta di Medicina; Universita di Milano; Via Vanvitelli 32 20129 Milan Italy