Selective and Potent Agonists and Antagonists for Investigating the Role of Mouse Oxytocin Receptors

Abstract

The neuropeptides oxytocin (OT) and vasopressin (AVP) have been shown to play a central role in social behaviors; as a consequence, they have been recognized as potential drugs to treat neurodevelopmental and psychiatric disorders characterized by impaired social interactions. However, despite the basic and preclinical relevance of mouse strains carrying genetic alterations in the OT/AVP systems to basic and preclinical translational neuroscience, the pharmacological profile of mouse OT/AVP receptor subtypes has not been fully characterized. To fill in this gap, we have characterized a number of OT and AVP agonists and antagonists at three murine OT/AVP receptors expressed in the nervous system as follows: the oxytocin (mOTR) and vasopressin V1a (mV1aR) and V1b (mV1bR) subtypes. These three receptors were transiently expressed in vitro for binding and intracellular signaling assays, and then a homology model of the mOTR structure was constructed to investigate how its molecular features compare with human and rat OTR orthologs. Our data indicate that the selectivity profile of the natural ligands, OT and AVP, is conserved in humans, rats, and mice. Furthermore, we found that the synthetic peptide [Thr 4 Gly 7 ]OT (TGOT) is remarkably selective for the mOTR and, like the endogenous OT ligand, activates G q and G i and recruits b-arrestins. Finally, we report three antagonists that exhibit remarkably high affinities and selectivities at mOTRs. These highly selective pharmacological tools will contribute to the investigation of the specific physiologic and pathologic roles of mOTR for the development of selective OT-based therapeutics.

Endogenous oxytocin inhibits hypothalamic corticotrophin‐releasing hormone neurones following acute hypernatraemia

“…As a first step towards testing that hypothesis, we again repeated experiments in slices obtained from animals injected with hypertonic saline, as presented in Figure 1D,E (red data plots), with two important changes. First, we used a more potent and selective oxytocin receptor antagonist, L‐368,899‐hydrochloride (L‐368) (1 μmol L −1 ) in place of Oxtr‐A . Second, in a subset of experiments, we replaced the GTP in the internal solution with 300 μmol L −1 GDP‐β‐S, a non‐hydrolysable analog of GDP that competitively inhibits G‐protein activation.…”

Developmental effects of vasotocin and nonapeptide receptors on early social attachment and affiliative behavior in the zebra finch

“…These dosages were based on those used in intracerebroventricular infusions in adults in Goodson et al, 2004 and scaled by 1/5, based on the changes in brain volume between adults versus juveniles (Ikebuchi et al, 2012). Both AVT and MC are predicted to act at multiple receptor subtypes in the zebra finch brain, including the VT4 (V1aR), VT3 (OT-like), and V2 receptors (Busnelli et al, 2013; Kruszynski et al, 1980; Leung et al, 2009; Manning et al, 2012). …”

Assembling the Puzzle: Pathways of Oxytocin Signaling in the Brain

“…Such quantity was calculated to correspond to a local concentration in the extracellular fluid of 1000 pg/mL (10) or, upon conversion in a nmol/L value, 1 nmol/L. Strikingly, the binding affinity of the OTRs for OT is around 1 nmol/L in all mammalian species (60,61). This means that at a concentration of 1 nmol/L, a considerable fraction of the receptors present at the cell surface is occupied and activated and will undergo internalization and desensitization.…”