Regional differences in oxytocin and vasopressin 1a receptor functionality in mouse embryonic brain development

There is mounting evidence that the oxytocin (Oxt) and vasopressin (Avp) systems contribute to early brain development. Work from transgenic mouse models as well as pharmacological manipulation of the Oxt and Avp systems suggests that signaling through the Oxt receptor (Oxtr) and the Avp 1a receptor (Avpr1a) during embryonic brain development affects behavior in adulthood. Unfortunately, at this time, very little is known or understood about where in the brain Oxtr and Avpr1a occurs during embryonic development or what the downstream consequences may be. To help provide some answers, Oxtr- and Avpr1a-stimulated G-protein coupled receptor binding assays were performed using guanosine 5'-(γ-thio)triphosphate, a non-hydrolyzable analog of guanosine triphosphate, to determine the functionality of the Oxtr and Avpr1a in both sexes at embryonic day (E) 14.5, E16.5, and E18.5. Based on previous work, we hypothesized that the Oxtr and Avpr1a would be functional in both sexes by E16.5 and activated by Oxt and Avp, respectively. The data suggest that while the Oxtr and Avpr1a are functional in both sexes starting at E16.5, where in the brain they are functional is not fully aligned with where there is known receptor binding. For the Oxtr, at E16.5, functional binding was observed in the ventricular and subventricular zones of the cortical and septal neuroepithelium and the amygdalar area, this shifted by E18.5 with functional binding observed only in the ventricular and subventricular septal neuroepithelium and the amygdalar area, with no functional binding observed in the ventricular and subventricular cortical neuroepithelium. For the Avpr1a, at E16.5, functional binding was only observed in the ventral hypothalamic area but by E18.5 functional binding was observed across numerous brain regions. Taken together, these data suggest that Oxtr and Avpr1a signaling is positioned to have site-specific effects on mouse brain development starting at E16.5.