Gestational immune activation disrupts hypothalamic neurocircuits of maternal care behavior.

Immune activation is one of the most common complications during pregnancy, predominantly evoked by viral infections. Nevertheless, how immune activation affects mother-offspring relationships postpartum remains unknown. Here, by using the polyinosinic-polycytidylic acid (Poly I:C) model of gestational infection we show that viral-like immune activation at mid-gestation persistently changes hypothalamic neurocircuit parameters in mouse dams and, consequently, is adverse to parenting behavior. Poly I:C-exposed dams favor non-pup-directed exploratory behavior at the expense of pup retrieval. These behavioral deficits are underlain by dendrite pruning and lesser immediate early gene activation in Galanin (Gal)+ neurons with dam-specific transcriptional signatures that reside in the medial preoptic area (mPOA). Reduced activation of an exclusively inhibitory contingent of these distal-projecting Gal+ neurons allows for increased feed-forward inhibition onto putative dopaminergic neurons in the ventral tegmental area (VTA) in Poly I:C-exposed dams. Notably, destabilized VTA output specifically accompanies post-pup retrieval epochs. We suggest that gestational immunogenic insults bias both threat processing and reward perception, manifesting as disfavored infant caregiving.

Orchestration of Dopamine Neuron Population Activity in the Ventral Tegmental Area by Caffeine: Comparison With Amphetamine.

BACKGROUND: Among psychostimulants, the dopamine transporter ligands amphetamine and cocaine display the highest addictive potential; the adenosine receptor antagonist caffeine is most widely consumed but less addictive. Psychostimulant actions of amphetamine were correlated with its ability to orchestrate ventral tegmental dopamine neuron activity with contrasting shifts in firing after single vs repeated administration. Whether caffeine might impinge on dopamine neuron activity has remained elusive. METHODS: Population activity of ventral tegmental area dopamine neurons was determined by single-unit extracellular recordings and set in relation to mouse behavior in locomotion and conditioned place preference experiments, respectively. RESULTS: A single dose of caffeine reduced population activity as did amphetamine and the selective adenosine A2A antagonist KW-6002, but not the A1 antagonist DPCPX. Repeated administration of KW-6002 or amphetamine led to drug-conditioned place preference and to unaltered or even enhanced population activity. Recurrent injection of caffeine or DPCPX, in contrast, failed to cause conditioned place preference and persistently reduced population activity. Subsequent to repetitive drug administration, re-exposure to amphetamine or KW-6002, but not to caffeine or DPCPX, was able to reduce population activity. CONCLUSIONS: Behavioral sensitization to amphetamine is attributed to persistent activation of ventral tegmental area dopamine neurons via the ventral hippocampus. Accordingly, a switch from acute A2A receptor-mediated reduction of dopamine neuron population activity to enduring A1 receptor-mediated suppression is correlated with tolerance rather than sensitization in response to repeated caffeine intake.

Secretagogin marks amygdaloid PKCδ interneurons and modulates NMDA receptor availability.

The perception of and response to danger is critical for an individual's survival and is encoded by subcortical neurocircuits. The amygdaloid complex is the primary neuronal site that initiates bodily reactions upon external threat with local-circuit interneurons scaling output to effector pathways. Here, we categorize central amygdala neurons that express secretagogin (Scgn), a Ca2+-sensor protein, as a subset of protein kinase Cδ (PKCδ)+ interneurons, likely "off cells." Chemogenetic inactivation of Scgn+/PKCδ+ cells augmented conditioned response to perceived danger in vivo. While Ca2+-sensor proteins are typically implicated in shaping neurotransmitter release presynaptically, Scgn instead localized to postsynaptic compartments. Characterizing its role in the postsynapse, we found that Scgn regulates the cell-surface availability of NMDA receptor 2B subunits (GluN2B) with its genetic deletion leading to reduced cell membrane delivery of GluN2B, at least in vitro. Conclusively, we describe a select cell population, which gates danger avoidance behavior with secretagogin being both a selective marker and regulatory protein in their excitatory postsynaptic machinery.

VEGF Treatment Ameliorates Depression-Like Behavior in Adult Offspring After Maternal Immune Activation.

Maternal immune activation (MIA) during pregnancy impacts offspring neurodevelopmental trajectories and induces lifelong consequences, including emotional and cognitive alterations. Using the polyinosinic:polycytidilic acid (PIC) MIA model we have previously demonstrated enhanced depression-like behavior in adult MIA offspring, which was associated with reduced expression of the vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) in the hippocampus. Since VEGF mediates the effects of various antidepressant agents, we here set out to explore whether VEGF administration could rescue the depression-like behavioral deficits in MIA offspring. To test our hypothesis, control and MIA offspring were intracerebroventricularly (i.c.v.) infused with either VEGF or vehicle solution and depression-related behavior was assessed in the sucrose preference test (SPT) and the tail suspension test (TST). As a surrogate of VEGF activity, the phosphorylation of the extracellular signal-regulated kinase (ERK) in hippocampus was quantified. We found that VEGF treatment reduced depression-related behavioral despair in the TST in MIA offspring but had no effect on anhedonia-like behavior in the SPT. While VEGF administration induced the phosphorylation of ERK in the hippocampus of control offspring, this effect was blunted in the MIA offspring. We conclude that VEGF administration, at the dosage tested, beneficially affects some aspects of the depression-like phenotype in the adult MIA offspring, inviting further studies using different dosage regimes to further explore the therapeutic potential of VEGF treatment in MIA-related changes in brain function and behavior.

Maternal immune activation during pregnancy impacts on brain structure and function in the adult offspring.

Gestational infection constitutes a risk factor for the occurrence of psychiatric disorders in the offspring. Activation of the maternal immune system (MIA) with subsequent impact on the development of the fetal brain is considered to form the neurobiological basis for aberrant neural wiring and the psychiatric manifestations later in offspring life. The examination of validated animal models constitutes a premier resource for the investigation of the neural underpinnings. Here we used a mouse model of MIA based upon systemic treatment of pregnant mice with Poly(I:C) (polyriboinosinic-polyribocytidilic acid), for the unbiased and comprehensive analysis of the impact of MIA on adult offspring brain activity, morphometry, connectivity and function by a magnetic resonance imaging (MRI) approach. Overall lower neural activity, smaller brain regions and less effective fiber structure were observed for Poly(I:C) offspring compared to the control group. The corpus callosum was significantly smaller and presented with a disruption in myelin/ fiber structure in the MIA progeny. Subsequent resting-state functional MRI experiments demonstrated a paralleling dysfunctional interhemispheric connectivity. Additionally, while the overall flow of information was intact, cortico-limbic connectivity was hampered and limbic circuits revealed hyperconnectivity in Poly(I:C) offspring. Our study sheds new light on the impact of maternal infection during pregnancy on the offspring brain and identifies aberrant resting-state functional connectivity patterns as possible correlates of the behavioral phenotype with relevance for psychiatric disorders.

Life-long impairment of glucose homeostasis upon prenatal exposure to psychostimulants.

Maternal drug abuse during pregnancy is a rapidly escalating societal problem. Psychostimulants, including amphetamine, cocaine, and methamphetamine, are amongst the illicit drugs most commonly consumed by pregnant women. Neuropharmacology concepts posit that psychostimulants affect monoamine signaling in the nervous system by their affinities to neurotransmitter reuptake and vesicular transporters to heighten neurotransmitter availability extracellularly. Exacerbated dopamine signaling is particularly considered as a key determinant of psychostimulant action. Much less is known about possible adverse effects of these drugs on peripheral organs, and if in utero exposure induces lifelong pathologies. Here, we addressed this question by combining human RNA-seq data with cellular and mouse models of neuroendocrine development. We show that episodic maternal exposure to psychostimulants during pregnancy coincident with the intrauterine specification of pancreatic ß cells permanently impairs their ability of insulin production, leading to glucose intolerance in adult female but not male offspring. We link psychostimulant action specifically to serotonin signaling and implicate the sex-specific epigenetic reprogramming of serotonin-related gene regulatory networks upstream from the transcription factor Pet1/Fev as determinants of reduced insulin production.

Lmo3 deficiency in the mouse is associated with alterations in mood-related behaviors and a depression-biased amygdala transcriptome.

The highly conserved transcription factor LIM-only 3 (Lmo3) is involved in important neurodevelopmental processes in several brain areas including the amygdala, a central hub for the generation and regulation of emotions. Accordingly, a role for Lmo3 in the behavioral responses to ethanol and in the display of anxiety-like behavior in mice has been demonstrated while the potential involvement of Lmo3 in the control of mood-related behavior has not yet been explored. Using a mouse model of Lmo3 depletion (Lmo3z), we here report that genetic Lmo3 deficiency is associated with altered performance in behavioral paradigms assessing anxiety-like and depression-like traits and additionally accompanied by impairments in learned fear. Importantly, long-term potentiation (LTP) in the basolateral amygdala (BLA), a proposed cellular correlate of fear learning, is impaired in Lmo3z mice. RNA-Seq analysis of BLA tissue and gene set enrichment analysis (GSEA) of differentially expressed genes in Lmo3z mice reveals a significant overlap between genes overexpressed in Lmo3z mice and those enriched in the amygdala of a cohort of patients suffering from major depressive disorder. Consequently, we propose that Lmo3 may play a role in the regulation of gene networks that are relevant to the regulation of emotions. Future work may aid to further explore the role of Lmo3 in the pathophysiology of affective disorders and its genetic foundations.

Influence of poly(I:C) variability on thermoregulation, immune responses and pregnancy outcomes in mouse models of maternal immune activation.

Maternal immune activation (MIA) models that are based on administration of the viral mimetic, poly(I:C), are widely used as experimental tools to study neuronal and behavioral dysfunctions in relation to immune-mediated neurodevelopmental disorders and mental illnesses. Evidence from investigations in non-pregnant rodents suggests that different poly(I:C) products can vary in terms of their immunogenicity, even if they are obtained from the same vendor. The present study aimed at extending these findings to pregnant mice, while also controlling various poly(I:C) products for potential contamination with lipopolysaccharide (LPS). We found significant variability between different batches of poly(I:C) potassium salt obtained from the same vendor (Sigma-Aldrich) in terms of the relative amount of dsRNA fragments in the high molecular weight range (1000-6000 nucleotides long) and with regards to their effects on maternal thermoregulation and immune responses in maternal plasma, placenta and fetal brain. Batches of poly(I:C) potassium salt containing larger amounts of high molecular weight fragments induced more extensive effects on thermoregulation and immune responses compared to batches with minimal amounts of high molecular weight fragments. Consistent with these findings, poly(I:C) enriched for high molecular weight dsRNA (HMW) caused larger maternal and placental immune responses compared to low molecular weight (LMW) poly(I:C). These variable effects were unrelated to possible LPS contamination. Finally, we found marked variability between different batches of the poly(I:C) potassium salt in terms of their effects on spontaneous abortion rates. This batch-to-batch variability was confirmed by three independent research groups using distinct poly(I:C) administration protocols in mice. Taken together, the present data confirm that different poly(I:C) products can induce varying immune responses and can differentially affect maternal physiology and pregnancy outcomes. It is therefore pivotal that researchers working with poly(I:C)-based MIA models ascertain and consider the precise molecular composition and immunogenicity of the product in use. We recommend the establishment of reference databases that combine phenotype data with empirically acquired quality information, which can aid the design, implementation and interpretation of poly(I:C)-based MIA models.

A role for miR-132 in learned safety.

Learned safety is a fear inhibitory mechanism, which regulates fear responses, promotes episodes of safety and generates positive affective states. Despite its potential as experimental model for several psychiatric illnesses, including post-traumatic stress disorder and depression, the molecular mechanisms of learned safety remain poorly understood, We here investigated the molecular mediators of learned safety, focusing on the characterization of miRNA expression in the basolateral amygdala (BLA). Comparing levels of 22 miRNAs in learned safety and learned fear trained mice, six safety-related miRNAs, including three members of the miR-132/-212 family, were identified. A gain-of-function approach based upon in-vivo transfection of a specific miRNA mimic, and miR-132/212 knock-out mice as loss-of-function tool were used in order to determine the relevance of miR-132 for learned safety at the behavioral and the neuronal functional levels. Using a designated bioinformatic approach, PTEN and GAT1 were identified as potential novel miR-132 target genes and further experimentally validated. We here firstly provide evidence for a regulation of amygdala miRNA expression in learned safety and propose miR-132 as signature molecule to be considered in future preclinical and translational approaches testing the transdiagnostic relevance of learned safety as intermediate phenotype in fear and stress-related disorders.

Enhanced synaptic plasticity and spatial memory in female but not male FLRT2-haplodeficient mice.

The Fibronectin Leucine-Rich Transmembrane protein 2 (FLRT2) has been implicated in several hormone -and sex-dependent physiological and pathological processes (including chondrogenesis, menarche and breast cancer); is known to regulate developmental synapses formation, and is expressed in the hippocampus, a brain structure central for learning and memory. However, the role of FLRT2 in the adult hippocampus and its relevance in sex-dependent brain functions remains unknown. We here used adult single-allele FLRT2 knockout (FLRT2+/-) mice and behavioral, electrophysiological, and molecular/biological assays to examine the effects of FLRT2 haplodeficiency on synaptic plasticity and hippocampus-dependent learning and memory. Female and male FLRT2+/- mice presented morphological features (including body masses, brain shapes/weights, and brain macroscopic cytoarchitectonic organization), indistinguishable from their wild type counterparts. However, in vivo examinations unveiled enhanced hippocampus-dependent spatial memory recall in female FLRT2+/- animals, concomitant with augmented hippocampal synaptic plasticity and decreased levels of the glutamate transporter EAAT2 and beta estrogen receptors. In contrast, male FLRT2+/- animals exhibited deficient memory recall and decreased alpha estrogen receptor levels. These observations propose that FLRT2 can regulate memory functions in the adulthood in a sex-specific manner and might thus contribute to further research on the mechanisms linking sexual dimorphism and cognition.

Maternal immune activation transgenerationally modulates maternal care and offspring depression-like behavior.

Gestational infection is increasingly being recognized for its involvement as causative mechanism in severe developmental brain abnormalities and its contribution to the pathogenesis of psychopathologies later in life. First observations in the widely accepted maternal immune activation (MIA) model based upon the systemic administration of the viral mimetic Polyinosinic:polycytidylic acid (poly(I:C)) have recently suggested a transmission of behavioral and transcriptional traits across generations. Although maternal care behavior (MCB) is known as essential mediator of the transgenerational effects of environmental challenges on offspring brain function and behavior, the possible propagation of alterations of MCB resulting from MIA to following generations has not yet been examined. Here we show that poly(I:C) stimulation at embryonic day 12.5 (E12.5) leads to aberrant MCB and that this effect is transmitted to the female F1 offspring. The transgenerational effects on MCB are paralleled by enhanced depression-like behavior in the second generation F2 offspring with contributions of both maternal and paternal heritages. Examination of offspring hippocampal expression of genes known as targets of MCB and relevant for ensuing non-genetic transmission of altered brain function and behavior revealed transgenerationally conserved and modified expressional patterns in the F1 and F2 generation. Collectively these data firstly demonstrate the transgenerational transmission of the impact of gestational immune activation on the reproductive care behavior of the mother. Behavioral and molecular characteristics of first and second generation offspring suggest transgenerationally imprinted consequences of gestational infection on psychopathological traits related to mood disorders which remain to be examined in future cross-fostering experiments.