Differential fate between oxytocin and vasopressin cells in the developing mouse brain

Abstract

Oxytocin (OXT) and arginine vasopressin (AVP), two neuropeptides involved in socio-emotional behaviors have been anatomically defined in the adult brain. Yet their spatial organization during postnatal development is not clearly defined. We built a developmental atlas using 3D imaging of cleared immunolabeled tissue over four early postnatal (P) stages, from birth (P0, P3, P7, P14) to young adulthood (≥P56). Our atlas-based mapping revealed that the number of OXT neurons doubles according to unique temporal dynamics in selective hypothalamic regions, namely, the periventricular and paraventricular nuclei, and in a novel location we named the antero-lateral preoptic. In the paraventricular nucleus, single-cell densities and fluorescence analysis demonstrated selective expansion of OXT cells in the antero-ventral division, whereas the postero-dorsal division contained cells present at birth. No changes were observed for AVP neurons. Our findings show the coexisting of innate and plastic OXT/AVP brain circuits probably triggered by environmental adaptation of the social brain.

Keywords: Developmental biology; Neuroscience; Optical imaging.

Graphical abstract

Figure 1

OXT and AVP cell expression in the developing and adult mice brains (A) Three-dimensional visualization of brain OXT (pseudo-colored gold dots) and AVP (pseudo-colored purple dots) neurons at birth (P0; left panel) and in adulthood (P ≥56). Representative flat images show volumetric (x-y-z-) positions of the immunoreactive cell bodies, pictured as dots using the Imaris tool spot detection module, in the coronal plane. Images are obtained from 817 tiff images (thickness of 1,634 μm). (B and C) (B) Brain OXT-Ir and (C) AVP-Ir cell number across development P0; P3, P7; P14 and P ≥56; n = 4–6 mice per age; ∗∗∗∗P < 0.0001 between the P3 and P ≥56 groups, ∗∗∗∗P <0.0001 between the P3 and P7 groups; ∗∗P < 0.01 between the P7 and P14 groups using one-way analysis of variance (ANOVA followed by Tukey's multiple-comparison test). Data are presented as mean ± SEM.

Figure 2

Spatiotemporal organization of OXT and AVP cells in the developing and adult hypothalamus (A) Representative maps of the hypothalamic OXT-Ir cells, represented as gold dots, and aligned into the Allen Brain atlas. Annotated regions are displayed as light gray volumes, at birth (P0; left panel) and in adulthood (P ≥56); coronal plane. At birth, the 3D cellular maps (n = 3 animals) were fitted in the adult reference space (n = 6 animals) for direct comparison. (B) Detailed quantitative analysis of the OXT-Ir in the PVN, PvPO, ALPO, MPN, SON, and TU across ages, denote unique sensitive periods of development for each brain region. n = 4–6 mice per age; ∗P <0.05; ∗∗P <0.01; ∗∗∗P <0.001 between groups using one-way analysis of variance (ANOVA followed by Tukey's multiple-comparison test). Data are presented as mean ± SEM; ns, comparisons not significant (p >0.05). (C) Representative maps of the hypothalamic AVP-Ir cells, represented as purple dots, and aligned into the Allen Brain atlas. (D) Detailed quantitative analysis of the AVP-Ir in the PVN, SON, MPN, and TU across ages. Scale bars, 100 μm. Regions and fibers: PVN, paraventricular nucleus; PvPO, periventricular preoptic nucleus; ALPO, antero-lateral preoptic nucleus; SON, supraoptic nucleus; MPN, medial preoptic nucleus, which includes accessory magnocellular nuclei, such as the anterior hypothalamic area, circular nucleus, and preoptic area; TU, tuberal nucleus; ADP, antero-dorsal preoptic nucleus; PS, para-striatal nucleus; PD, postero-dorsal preoptic nucleus; and aco, anterior commissure; fx, fornix. Anatomical axes: D, dorsal; V, ventral; A, anterior; P, posterior.

Figure 3

Immunofluorescence labeling of OXT cells in the ALPO Images of the OXT immunofluorescence labeling in the ALPO and PVN nuclei at birth (P0; left column) and in adulthood (P >56; middle column) are shown in coronal (top), sagittal (middle), and horizontal (bottom) planes. 3D mapping of the ALPO nucleus: corresponding registered OXT cell volumes (light gold) are shown. Scale bars, 100 μm. Regions and fibers: ALPO, antero-lateral preoptic nucleus; PVN, paraventricular nucleus; ADP, antero-dorsal preoptic nucleus; PS, para-striatal nucleus; and aco, anterior commissure; fx, fornix.

Figure 4

OXT cell expansion and AVP reorganization cells in the paraventricular nucleus (A) Double immunofluorescence labeling of OXT- (gold) and AVP-Ir cells (magenta) in the PVN, at birth (PO; left) and in adulthood (P56; right). Coronal (top), horizontal (middle), and sagittal (bottom) planes are displayed. Scale bars, 100 μm. (B) 3D plotting and flat mapping summarizing average Cartesian coordinates (in μm) of the OXT (gold dots) and AVP (magenta dots) neurons for each age group (n = 3 mice at P0, P3, P7, P14; n = 6 mice at P ≥56). Coronal (top), horizontal (middle), and sagittal (bottom) views illustrate the specific spatiotemporal arrangements of OXT- and AVP-PVN networks. (C) 3D representation of the molecular volume occupied by OXT cells (yellow dots in yellow volume) and AVP cells (magenta dots in magenta volume) across development. The ratio between OXT and AVP volume occupancy, expressed as percentage of the total PVN is included on the side for each age group.

Figure 5

Developmental changes of OXT cells along the antero-posterior axis of the paraventricular nucleus (A) Cell-based density distribution of OXT cells in the PVN across development. Sub-areas of high (yellow-orange; >100 cells/μm³), intermediate (green; 60–100 cells//μm³), and low (blue; <60 cells/μm³) densities are displayed in coronal (top) and sagittal (bottom) planes. (B) 3D modeling illustrating the antero-posterior clustering within the OXT cell population in the PVN across development. (C) Cell quantification of OXT-Ir cells located in the anterior and posterior clusters. (D) 3D representation of the animal-based z-transformed fluorescence intensity level for each OXT cell in the anterior (gray volume) and posterior (blue) clusters across development. (E) Group analysis of the mean relative fluorescence in the anterior and posterior clusters.