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Low platelet MAO activity in chronic schizophrenics: a long-term effect of neuroleptic treatment?
Abstract:
Platelet MAO activity was determined, using 14C-tryptamine and 14C-beta-phenylethylamine as substrates, in two groups of schizophrenic patients and a normal control population. The first patient group consisted of 75 schizophrenics who had been medication-free for 2 weeks and had not been exposed to neuroleptic drugs for at least 2 months before the off-drug period. The second patient group comprised 55 schizophrenics who were on treatment with haloperidol for at least 2 months. The enzyme activity was found to be significantly decreased in both drug-free (using only tryptamine as substrate, P less than 0.05) and haloperidol-treated (P less than 0.001) chronic schizophrenics as compared with normal controls, and to be significantly lower (P less than 0.05) in haloperidol-treated than in off-drug chronic schizophrenics. An in vitro study confirmed the lowering effect of haloperidol on MAO activity. It is suggested that low platelet MAO values observed in chronic schizophrenics might be in part an effect of neuroleptic treatment.
Insights
Platelet monoamine oxidase (MAO) activity is reduced in chronic schizophrenic patients. Haloperidol treatment further decreases MAO activity, suggesting neuroleptic medication contributes to lower enzyme levels in schizophrenia.
Area of Science:
- Neuroscience
- Biochemistry
- Psychiatry
Background:
- Platelet monoamine oxidase (MAO) activity has been investigated as a potential biomarker in schizophrenia.
- Previous studies suggest alterations in MAO activity in psychiatric disorders, but findings in schizophrenia are varied.
Purpose of the Study:
- To investigate platelet MAO activity in medication-free and haloperidol-treated chronic schizophrenic patients compared to healthy controls.
- To determine the in vitro effect of haloperidol on MAO activity.
Main Methods:
- Platelet MAO activity was measured using 14C-tryptamine and 14C-beta-phenylethylamine as substrates.
- Study included 75 medication-free schizophrenics, 55 haloperidol-treated schizophrenics, and a normal control group.
- In vitro experiments assessed haloperidol's direct impact on MAO activity.
Main Results:
- Significantly decreased platelet MAO activity was observed in both medication-free (P < 0.05) and haloperidol-treated (P < 0.001) schizophrenics compared to controls.
- Haloperidol-treated patients exhibited significantly lower MAO activity than medication-free patients (P < 0.05).
- In vitro studies confirmed haloperidol reduces MAO activity.
Conclusions:
- Reduced platelet MAO activity is present in chronic schizophrenia, irrespective of recent medication.
- Haloperidol treatment appears to further lower MAO activity in schizophrenic patients.
- Low platelet MAO levels in chronic schizophrenia may be partly attributed to neuroleptic treatment effects.