The authors found higher in vitro 14C-tryptamine half-lives in the blood
of 10 drug-free chronic schizophrenic patients than in the blood of 13
mentally normal control subjects. This finding was negatively correlated
for both groups with platelet MAO activity. Repeated determinations of in
vitro 14C-tryptamine half-lives over a period of 5 months were positively
correlated for the patients, although some blood samples showed
statistically significant variability.