Effect of loxapine on peripheral dopamine-like and serotonin receptors in patients with schizophrenia.
OBJECTIVE
To investigate the effect of loxapine on peripheral dopamine D2-like and serotonin receptor binding and on psychotic symptoms.


METHODS
Patients (n = 24) meeting the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, for schizophrenia were selected from an outpatient clinic (age range 18-70 yr).


METHODS
Patients were given loxapine (dose determined by a physician) for a period of 12 weeks. There were clinic visits at before treatment began and at 6 weeks and 12 weeks of treatment. Scores on a variety of efficacy and safety scales were recorded at each visit, and blood was drawn for receptor assays.


RESULTS
Patients showed significant improvement on most psychiatric assessment scales after 6 and 12 weeks of treatment with loxapine, and both lymphocyte D2-like and 5-HTL2A platelet receptor binding were down-regulated after 6 and 12 weeks. The degree of receptor down-regulation was not significantly correlated with improvements in psychotic symptoms, however.


CONCLUSIONS
Loxapine down-regulated both lymphocyte D2-like and platelet 5-HT2A receptors to the same extent, suggesting that both receptors are involved in the mechanism of action of loxapine in patients with schizophrenia.
Singh
Amarendra N
AN
Department of Psychiatry, Queen's University, Kingston, Ont. singha@post.queensu.ca
Barlas
Cia
C
Saeedi
Huma
H
Mishra
Ram K
RK
D000328:Adult; D014150:Antipsychotic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D018492:Dopamine Antagonists / Q000009:adverse effects / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008152:Loxapine / Q000009:adverse effects / Q000627:therapeutic use*; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism; D008238:Lysergic Acid Diethylamide / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D011869:Radioligand Assay; D044402:Receptor, Serotonin, 5-HT2A; D017448:Receptors, Dopamine D2 / Q000187:drug effects* / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012559:Schizophrenia / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D012565:Schizophrenic Psychology; D016896:Treatment Outcome
D014150:Antipsychotic Agents; D018492:Dopamine Antagonists; D044402:Receptor, Serotonin, 5-HT2A; D017448:Receptors, Dopamine D2; D011985:Receptors, Serotonin; D008238:Lysergic Acid Diethylamide; D008152:Loxapine