Postmortem measurements of neuropeptides in human brain

Met-enkephalin concentrations in caudate nuclei are decreased in chronic paranoid schizophrenic patients; met-enkephalin concentrations in caudate nuclei are increased in opiate abusers; and substance P concentrations in caudate nuclei are increased in some patients with psychoses other than schizophrenia. The significance of these findings remains to be determined. Although drugs may account for these findings, especially in opiate abusers, they do not appear to be responsible for the other findings. With regard to substance P concentrations, further studies with patients with affective psychoses should be considered. Regardless, the postmortem approach for testing hypotheses that neuropeptides are involved in mental illness appears to be a promising one.