Further studies on the endogenous inhibitor of monoamine oxidase in schizophrenic plasma

Platelet-free plasma from schizophrenic patients satisfying research diagnostic criteria for chronic schizophrenia was obtained and mixed with platelet-rich plasma from normal controls. Decreases in control platelet monoamine oxidase activity were observed, with some control platelets apparently much more sensitive than others to the inhibitory activity of the chronic schizophrenic plasma. Experimental conditions and selection from sensitive control individuals seem crucial in demonstrating the presence of endogenous inhibitors in schizophrenics' plasma.