Difficulties in comparing catecholamine-related enzymes from the brains of schizophrenics and controls.

The catecholamine-forming and metabolizing enzyme tyrosine hydroxylase, dopa decarboxylase, dopamine-beta-hydroxylase, phenylethanolamine N-methyltransferase, and catecholamine-O-methyltransferase, as well as the endogenous inhibitor of dopamine-beta-hydroxylase were compared in the brains of schizophrenics and controls. While there were no statistically significant differences in the enzyme or inhibitor activity between groups, tbre was a decided trend toward a decreased enzyme activity in the brains of the schizophrenics. From another set of control brains it was found that changes in human enzyme activity following death are variable and may be dependent on how the brains were handled. Thus, it is unclear whether the apparent differences between schizophrenics and controls were present when they were alive or occurred after death.