Since discovery of endogenous morphine (endorphin) from the brain tissue of pig, this substance has been recognized as a new neurotransmitter candidate. In psychiatric field, several researchers have reported considerable relation between -endorphin activity and schizophrenia, whereas definite relationship has not yet been -established due to contradictory findings of research.
The author performed this study to investigate possible change of plasma endorphin level- in chronic schizophrenic patients and to clarify possible influence of antipsychotic drug on the level.
Twenty five chronic schizophrenic patients and 9 normal controls were randomly selected for the study and the patients were devided into two groups; drug-free, group and haloperidol group. The drug-free group consisted of 11 cases switched by placebo for 14 days prior to blood sampling. And the haloperidol group consisted of 14 cases to whom 10-15mg of haloperidol were medicated orally of 14 days. Five -ml. of blood was sampled at 9 : 00,9 : 30 a.m. on the 15 th day in a fasting state and plasma level of j3-endorphin-like substance was measured by radioimmunoassay -procedure.
Criterion of increased level of the substance was determined to be 25 pg/ml according to the fact that the lowest measurable level in this procedure was 20 pg/ -ml and the levels of the substance were below the lowest level in 88% of normal ,sample. The cases of increased /3-endorphin-like substance could be found to be 5 among 11 cases (45.5%) in drug-free group, 3 among 14 cases (21.4%) in haloperidol group, and none among 9 cases in control group (0.05> 05>p>0.025).
This finding presumably suggests that plasma endorphin level increases in chronic schizophrenics and dopamine antagonist, haloperidol possibly suppresses endorphin level. The previous researchers confirmed increased activity of endorphin in acute schizophrenics but contradictory findings in chronic cases. The findings of normal -endorphin activity in chronic schizophrenics could be explained from the fact that previous antipsychotic medication could give influence on the endorphin activity.
Finally, possible mechanisms of action of endorphin in relation to schizophrenic manifestation were discussed with experimental findings and hypotheses of the previous researchers.
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