Related Experiment Video
Updated: Aug 14, 2026

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
Published on: February 20, 2018
Influence of calmodulin antagonist (stelazine) on agonist-induced calcium mobilization and platelet activation
1Department of Laboratory Medicine and Pathology, University of Minnesota Health Sciences Center, Minneapolis 55455.
Abstract:
Phenothiazines at high concentrations inhibit platelet aggregation and the secretion of granule contents. In this study we have evaluated the influence of stelazine on platelet function at low concentrations. Stelazine alone had no influence on resting calcium levels in platelets but facilitated agonist-induced elevation of cytosolic calcium. Platelets combined with low concentrations of stelazine (10 microM) and stimulated with subthreshold concentrations of thrombin (0.05 mu/ml) aggregated irreversibly and released significant quantities of ATP. Results of these studies suggest a new role for the calmodulin antagonist stelazine in platelet activation.
Related Concept Videos
Drugs that Stabilize Microtubules
Amplifying Signals via Second Messengers
Feedback Regulation of Calcium Concentration
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Intracellular Signaling Affects Focal Adhesions
Some...
Ligand-Gated Ion Channel Receptor: Gating Mechanism

