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Dopamine receptor responsivity in schizophrenic patients before and after switch from haloperidol to risperidone
M Markianos1, J Hatzimanolis, L Lykouras
1Athens University Medical School, Psychiatric Clinic, Eginition Hospital, Greece. markian@otenet.gr
Psychiatry Research
|January 26, 2000
Summary
The haloperidol (HAL) test measures dopamine receptor activity in schizophrenia patients. Risperidone treatment significantly improved symptoms but abolished HAL test prolactin (PRL) responses, indicating altered D2 receptor function.
Area of Science:
- Neuroscience
- Pharmacology
- Psychiatry
Background:
- Plasma prolactin (PRL) increases after haloperidol (HAL) administration reflect D2 dopamine receptor responsivity.
- This HAL test may indicate neuroleptic D2 receptor occupancy in schizophrenic patients.
Purpose of the Study:
- To investigate D2 dopamine receptor responsivity using the HAL test in schizophrenic patients during haloperidol and risperidone treatment.
- To assess the impact of risperidone on prolactin levels and psychiatric symptoms.
Main Methods:
- 12 male schizophrenic patients received haloperidol, followed by risperidone.
- The haloperidol (HAL) test was administered during both treatment phases.
- Brief Psychiatric Rating Scale (BPRS) scores were evaluated.
Main Results:
- Risperidone treatment reduced BPRS total scores by 38% and subscale scores for positive, negative, and general symptoms.
- Moderate PRL responses to the HAL test occurred during haloperidol treatment.
- No PRL responses to the HAL test were observed during risperidone treatment, with a significant increase in baseline PRL.
Conclusions:
- Risperidone effectively treats schizophrenia symptoms.
- Risperidone significantly elevates baseline prolactin levels and blocks the PRL response to the HAL test.
- This effect suggests a complex interaction with D2 dopamine receptors, potentially beyond simple blockade.