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Updated: Aug 16, 2026

Characterization of G Protein-coupled Receptors by a Fluorescence-based Calcium Mobilization Assay
Published on: July 28, 2014
Could dual G-protein coupling explain [D-Met2]FMRFamide's mixed action in vivo?
1Drug Discovery, R. W. Johnson Pharmaceutical Research Institute, Spring House, PA 19477, USA.
Abstract:
In vitro studies have demonstrated that FMRFamide-related peptide receptors can be coupled to different G-proteins, mediating opposite stimulatory and inhibitory effects. The present study tested whether this duality might extend to effects in vivo. Antinociception in mice of ICV [D-Met2]FMRFamide, which produced agonist [ED50 = 36.3 micrograms (61.6 nmol)] and antagonist [ID50 = 0.72 microgram (1.22 nmol)] actions, was attenuated by 24-h pretreatment with ICV pertussis toxin (ID50 = 0.55 microgram) or cholera toxin (ID50 = 0.09 microgram), suggesting that [D-Met2]FMRFamide in vivo effects might also be explained by dual Gi/Gs, coupling.
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