1. Assembling the Puzzle: Pathways of Oxytocin Signaling in the Brain
Valery Grinevich, H. Sophie Knobloch-Bollmann, Marina Eliava, Marta Busnelli, Bice Chini 
Biological Psychiatry 
Volume 79, Issue 3, Pages (February 2016)
DOI: /j.biopsych
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions

2. Figure 1
Schemas of pathways of oxytocin (OT) delivery in evolution and ontogenesis. Left panel represents transformation in the vertebrate evolution of magnocellular nuclei from preoptic nucleus (basal vertebrates) to paraventricular, supraoptic, and accessory nuclei (advanced vertebrates). In parallel, individual magnocellular neurons change morphology and interposition within the wall of the third ventricle. Along evolution, magnocellular neurons form collaterals, which project to extrahypothalamic regions concomitantly with classic projections to the posterior pituitary. Right panel demonstrates ontogenesis of the magnocellular OT system in rodents, which has common features with evolution: magnocellular neurons originate from the one source (the wall of the diamond-shaped third ventricle), migrate in a lateroventral direction, forming a polycentric OT system. Individual neurons undergo the process of maturation and specialization from bipolar neurons in newborns to multipolar neurons carrying rich dendritic trees and bifurcating axons. AN, accessory nuclei; E9 and E12.5, embryonic days 9 and 12.5; NH, neurohypophysis; OCh, optic chiasm; P1 and P21, postnatal days 1 and 21; PON, preoptic nucleus; PP, posterior pituitary lobe; PVN, paraventricular nucleus; SON, supraoptic nucleus; 3V, third ventricle.
Biological Psychiatry  , DOI: ( /j.biopsych )
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions

3. Figure 2
Three-dimensional reconstruction of projections of three individual oxytocin (OT) neurons using light-sheet microscopy. The cleared rat brain (female) contains virally mediated Venus labeling unilaterally in OT neurons of the paraventricular nucleus (PVN). (A) Depicted is a horizontal light sheet at the level of the PVN in the ventral brain showing the unilateral Venus labeling of OT neurons. Anterior (a) and posterior (p) are indicated. (B) Magnocellular OT cells at the edge of the caudal PVN were chosen for tracing of single cells in horizontal view by focusing along z. Color code of tracing skeletons indicate fibers emanating from different cell somata (g, green; b, blue; r, red cell). Somata indicated by circles. (C) Fibers of three neurons were traced until the Venus signal became too faint to follow further. The tracing revealed four to five fibers emanating from the soma (g = 4; b = 4; r = 5 main fibers) and if further branched, bifurcate one to four times along the fiber (g = 8/0; b = 3/2; r = 1 total # of subbranches/4 unbranched fibers). Venus fluorescence was recorded from the uncut translucent brain on a custom-built light-sheet microscope controlled by custom acquisition software based on Labview 8.6 (91); mosaic tiles were stitched with a plugin written for ImageJ/Fiji (86) and axons were traced with Knossos software (87) in cooperation with Dr. Günter Giese, Max Planck Institute for Medical Research, Heidelberg, Germany. Scale bars represent 1 µm (A) and 350 μm (C). Somata indicated by circles. cp, cerebral peduncle; d, dorsal; H, hippocampus; SNR, substantia nigra, reticular part; 3V, third ventricle; v, ventral.
Biological Psychiatry  , DOI: ( /j.biopsych )
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions

4. Figure 3
Potential evolutionary trajectories of the nonapeptide system in vertebrates. Parallel evolution of ligands and receptor genes is based on comparative analysis of chromosomal location and sequence information (20). The differentiation of the magnocellular system is based on the analysis of neuropeptide expression and neuroanatomical morphology in the brain of basal and advanced vertebrates (6). AVP, vasopressin; MS, mesotocin; MYA, million years ago; OT, oxytocin; VT, vasotocin.
Biological Psychiatry  , DOI: ( /j.biopsych )
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions

5. Figure 4
Expression of oxytocin receptors (OTRs) within the mesolimbic social decision-making network (28) in four classes of vertebrates. Autoradiography, in situ hybridization, and immunohistochemistry studies presented in the literature are schematically summarized here; references include for teleosts (88); for songbirds (32,33); for rodents (15,89); and for primates (29,35,37,38). Areas of the mesolimbic social decision making network include: nucleus accumbens (NAcc); ventral pallidum (VP); lateral septum (LS); preoptic area (POA); ventromedial nucleus of hypothalamus (VMH); basolateral amygdala (blAMY); medial amygdala, (meAMY); bed nucleus of the stria terminalis (BNST); anterior hypothalamus (AH); hippocampus (HIP); ventral tegmental area (VTA); periaqueductal gray (PAG); and striatum (Str). Teleost areas of the network (A) include: anterior nucleus tuberal (aNT), lateral pallial (dorsal) part of the telencephalon (Dl); medial pallial (dorsal) part of the telencephalon (Dm); periventricular nucleus of the posterior tuberculum (TPp); central part of subpallial (ventral) telencephalon (Vc); dorsal nucleus of subpallial (ventral) telencephalon (Vd); ventral tuberal nucleus (VnT); supracommissural nucleus of subpallial (ventral) telencephalon (Vs); ventral part of subpallial (ventral) telencephalon (Vv). Other areas involved in social behavior depicted here include: medial septum (MS); high vocal center (HVC); robust nucleus of the arcopallium (RA); and motor nucleus of the XII cranial nerve (XII) in panel (B); olfactory bulb (Ob) and anterior olfactory nucleus (AON) in panel (C); nucleus basalis of Meynert (NBM); superior colliculus (SuC); pedunculopontine tegmental nucleus (PPT); and trapezoid body (TB) in panel (D).
Biological Psychiatry  , DOI: ( /j.biopsych )
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions

6. Figure 5
Oxytocin (OT) axons in the forebrain of lactating rat. Using monoclonal antibodies against mature form of OT generated by the Harlod Gainer team (90) followed by diaminobenzidine-based method of visualization, axons containing OT immune product were detected in previously known places such as the lateral septum (LS), nucleus accumbens core (AcbC), and central nucleus of amygdala (CeA). In addition, OT-immunoreactive axons can be visualized in the hippocampus (CA1), barrel field (S1BF) of the somatosensory cortex, and septohippocampal nucleus (Shi)—structures that are devoid of OT immunosignal in nonlactating rats. The latter suggests that the functional state may activate both synthesis and transport of OT along axons to various forebrain regions.
Biological Psychiatry  , DOI: ( /j.biopsych )
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions

7. Figure 6
Spatial distribution of oxytocin receptors (OTR) and oxytocin (OT) axons in the rat brain. For the OTR topography, the results obtained using autoradiography and in situ hybridization are summarized here and derive from references (34,49–52). Distribution of OT fibers derives from the analysis of studies that used immunohistochemical techniques (48) and that employed viral vector-based techniques in association with soluble fluorescent marker Venus to fill and visualize OT axons (16). There is a basically complete overlap between OTR and OT fibers and an apparent mismatch is limited to four regions that express OTR but do not receive direct OT projections. These regions are the olfactory bulb (Ob), ventral pallidum (VP), medial preoptic area (POA), and ventromedial nucleus of hypothalamus (VMH). AH, anterior hypothalamus; AON, anterior olfactory nucleus; blAMY, basolateral amygdala; BNST, bed nucleus of the stria terminalis; HIP, hippocampus; LS, lateral septum; NAcc, nucleus accumbens; meAMY, medial amygdala; PAG, periaqueductal gray; Str, striatum; VTA, ventral tegmental area.
Biological Psychiatry  , DOI: ( /j.biopsych )
Copyright © 2016 Society of Biological Psychiatry Terms and Conditions