Calcium mobilization in platelets from schizophrenic and healthy subjects. Regulation by lithium and neuroleptics

Area of Science:

• Neuroscience
• Biochemistry
• Pharmacology

Background:

• Intracellular calcium (Ca2+) signaling is crucial for platelet function.
• Dysregulation of calcium homeostasis has been implicated in psychiatric disorders.

Purpose of the Study:

• To investigate the effects of thrombin, neuroleptics (chlorpromazine, haloperidol), and lithium on intracellular calcium concentrations ([Ca2+]i) in human platelets.
• To compare platelet calcium responses between healthy volunteers and schizophrenic patients on neuroleptic medication.

Main Methods:

• Measurement of intracellular free calcium concentrations ([Ca2+]i) in platelets using spectrofluorometry.
• Dose-response studies with thrombin, chlorpromazine, haloperidol, and lithium.
• Assessment of drug interactions and additive effects on calcium mobilization.
• Comparison of platelet responses between healthy controls and schizophrenic patients.

Main Results:

• Thrombin, chlorpromazine, and haloperidol dose-dependently increased [Ca2+]i, suggesting a common calcium pool, likely the dense tubular system.
• Lithium also increased [Ca2+]i but acted on a separate pool, with additive effects when combined with the other drugs.
• Platelets from schizophrenic patients exhibited a significantly reduced response to thrombin compared to healthy volunteers.

Conclusions:

• Neuroleptics and lithium differentially modulate platelet calcium signaling pathways.
• Schizophrenia may be associated with altered platelet calcium handling, potentially due to the disease itself or chronic neuroleptic treatment.
• Further research is needed to elucidate the underlying mechanisms and clinical implications of these findings.