Atosiban

Record the receptor panel actually measured. Absence of a result for another receptor does not establish absence of activity.

In cellular models expressing the human oxytocin receptor, atosiban antagonized Gq coupling while acting as an agonist in Gi-mediated signaling. This functional discrimination does not make it a universal agonist or antagonist of every response attributed to the receptor.

A 2005 study combined G-protein activation assays with cell-growth observations. Atosiban was associated with reduced growth in vitro in HEK293 and MDCK cells with an introduced receptor and in DU145 cells with endogenous expression. This local result does not by itself describe an endocrine response or a human application.

Later research used biosensors to distinguish individual members of the Gi/o family. Atosiban was among the ligands capable of separating responses across G-protein subtypes in cellular models. Calling this only Gi signaling loses resolution provided by the method and can conceal differences between apparently similar analogues.

The cited studies also examined internalization and beta-arrestin recruitment. For the selective ligands described, G-protein signaling was not accompanied by all those responses in vitro. The comparison separates initial activation, receptor regulation and later cellular outcomes without assuming an obligatory sequence shared by every ligand.