Several years ago it was observed that iproniazid (nicotinic isopropylhydrazide) used in the treatment of tuberculous patients produced a euphoria in those who were depressed. This chance observation opened a whole realm of study. Iproniazid is now recognized not only as an antibiotic but as one of a large class of psychostimulant or psychoenergizers. These drugs, together with the tranquilizers, have had vast effects on psychiatry. Other and later serendipitous observations have given iproniazid and similar agents a role in diseases more commonly recognized as organic.
Many of the psychostimulants act as inhibitors of the enzyme monoamine oxidase (MAO), and it is this general property which is the subject of the present volume. Epinephrine, norepinephrine, histamine, dopamine, and serotonin are examples of biologically active monoamines normally oxidized by MAO. Increased rabbit brain stem concentrations of serotonin and norepinephrine result from treatment with even a single dose of iproniazid. If epinephrine