Department of Psychiatry (Hess, Hutchinson, Gould), Department of Neurobiology (Gould), and Department of Pharmacology (Gould), University of Maryland School of Medicine, Baltimore; Experimental Therapeutics and Pathophysiology Branch, NIMH, Bethesda, Md. (Greenstein, Zarate); Baltimore Veterans Affairs Medical Center, Veterans Affairs Maryland Health Care System, Baltimore (Gould).