Altered gene expression and spine density in nucleus accumbens of adolescent and adult male mice exposed to emotional and physical stress.

Stressful early life experiences are implicated in lifelong health. However, little is known about the consequences of emotional stress (ES) or physical stress (PS) on neurobiology. Therefore, the following set of experiments was designed to assess changes in transcription and translation of key proteins within the nucleus accumbens (NAc). Male adolescent (postnatal day 35) or adult (8-week-old) mice were exposed to ES or PS using a witness social defeat paradigm. Then, 24 h after the last stress session, we measured levels of specific mRNAs and proteins within the NAc. Spine density was also assessed in separate groups of mice. Exposure to ES or PS disrupted extracellular signal-related kinase 2 (ERK2), reduced transcription of ΔFosB and had no effect on cAMP response element-binding protein (CREB) mRNA. Western blots revealed that exposure to ES or PS decreased ERK2 phosphorylation in adolescents, whereas the same stress regimen increased ERK2 phosphorylation in adults. Exposure to ES or PS had no effect on ΔFosB or CREB phosphorylation. ES and PS increased spine density in the NAc of adolescent exposed mice, but only exposure to PS increased spine density in adults. Together, these findings demonstrate that exposure to ES or PS is a potent stressor in adolescent and adult mice and can disturb the integrity of the NAc by altering transcription and translation of important signaling molecules in an age-dependent manner. Furthermore, exposure to ES and PS induces substantial synaptic plasticity of the NAc.

AVPR1A distribution in the whole C57BL/6J mouse neonate.

The neuropeptide arginine vasopressin (AVP) plays significant roles in maintaining homeostasis and regulating social behavior. In vaginally delivered neonates, a surge of AVP is released into the bloodstream at levels exceeding release during life-threatening conditions such as hemorrhagic shock. It is currently unknown where the potential sites of action are in the neonate for these robust levels of circulating AVP at birth. The purpose of this study is to identify the location of AVP receptor 1a (AVPR1A) sites as potential peripheral targets of AVP in the neonatal mouse. RT-qPCR analysis of a sampling of tissues from the head demonstrated the presence of Avpr1a mRNA, suggesting local peripheral translation. Using competitive autoradiography in wildtype (WT) and AVPR1A knockout (KO) postnatal day 0 (P0) male and female mice on a C57BL/6J background, specific AVPR1A ligand binding was observed in the neonatal mouse periphery in sensory tissues of the head (eyes, ears, various oronasal regions), bone, spinal cord, adrenal cortex, and the uro-anogenital region in the neonatal AVPR1A WT mouse, as it was significantly reduced or absent in the control samples (AVPR1A KO and competition). AVPR1A throughout the neonatal periphery suggest roles for AVP in modulating peripheral physiology and development of the neonate.

Oxytocin Receptor Binding Sites in the Periphery of the Neonatal Prairie Vole.

The oxytocin receptor (OXTR) has been observed in the periphery of neonatal C57BL/6J mice (Mus musculus), including facial regions and the anogenital area. In those studies, ligand specificity was confirmed with a congenital OXTR knockout mouse as well as competitive binding techniques. The aim of this study was to determine if OXTR is present in the same peripheral sites in the neonatal prairie vole (Microtus ochrogaster) for cross-species comparisons. Receptor autoradiography was performed on 20 µm sagittal sections of whole postnatal day 0 (P0) male and female prairie voles using the 125iodinated-ornithine vasotocin ([125I]-OVTA) radioligand. A competition binding assay was used to assess the selectivity of [125I]-OVTA for peripheral OXTR. Radioactive ligand (0.05 nM [125I]-OVTA) was competed against concentrations of 0 and 1000 nM excess unlabeled oxytocin (OXT). Previously identified regions of significant OXTR ligand binding in the mouse were analyzed for comparison: rostral and lateral periodontium, olfactory epithelium, ciliary bodies of the eye, whisker pads, adrenal gland, and anogenital area. We also evaluated the liver and scapular brown adipose tissue, which displayed strong but non-specific signal on film in mice. While there were some areas that showed conserved OXTR ligand binding in the prairie vole (e.g., ciliary body of the eye and the anogenital area), areas showing OXTR ligand binding in the neonatal prairie vole were not identical to OXTR ligand binding in the periphery of the C57BL/6J neonatal mouse. Further, some of the regions measured in the prairie vole suggest sex differences in OXTR ligand binding. Collectively, as is well-established in the central nervous system, these data indicate that patterns of OXTR ligand binding in the infant periphery are species-specific.

Oxytocin receptor binding sites in the periphery of the neonatal mouse.

Oxytocin (OXT) is a pleiotropic regulator of physiology and behavior. An emerging body of evidence demonstrates a role for OXT in the transition to postnatal life of the infant. To identify potential sites of OXT action via the OXT receptor (OXTR) in the newborn mouse, we performed receptor autoradiography on 20 µm sagittal sections of whole postnatal day 0 male and female mice on a C57BL/6J background using the 125iodinated ornithine vasotocin analog ([125I]-OVTA) radioligand. A competitive binding assay on both wild-type (WT) and OXTR knockout (OXTR KO) tissue was used to assess the selectivity of [125I]-OVTA for neonatal OXTR. Radioactive ligand (0.05 nM [125I]-OVTA) was competed against concentrations of 0 nM, 10 nM, and 1000 nM excess unlabeled OXT. Autoradiographs demonstrated the high selectivity of the radioligand for infant peripheral OXTR. Specific ligand binding activity for OXTR was observed in the oronasal cavity, the eye, whisker pads, adrenal gland, and anogenital region in the neonatal OXTR WT mouse, but was absent in neonatal OXTR KO. Nonspecific binding was observed in areas with a high lipid content such as the scapular brown adipose tissue and the liver: in these regions, binding was present in both OXTR WT and KO mice, and could not be competed away with OXT in either WT or KO mice. Collectively, these data confirm novel OXT targets in the periphery of the neonate. These peripheral OXTR sites, coupled with the immaturity of the neonate's own OXT system, suggest a role for exogenous OXT in modulating peripheral physiology and development.