Got milk? Maternal immune activation during the mid-lactational period affects nutritional milk quality and adolescent offspring sensory processing in male and female rats.

Previous studies have underscored the importance of breastfeeding and parental care on offspring development and behavior. However, their contribution as dynamic variables in animal models of early life stress are often overlooked. In the present study, we investigated how lipopolysaccharide (LPS)-induced maternal immune activation (MIA) on postnatal day (P)10 affects maternal care, milk, and offspring development. MIA was associated with elevated milk corticosterone concentrations on P10, which recovered by P11. In contrast, both milk triglyceride and percent creamatocrit values demonstrated a prolonged decrease following inflammatory challenge. Adolescent MIA offspring were heavier, which is often suggestive of poor early life nutrition. While MIA did not decrease maternal care quality, there was a significant compensatory increase in maternal licking and grooming the day following inflammatory challenge. However, this did not protect against disrupted neonatal huddling or later-life alterations in sensorimotor gating, conditioned fear, mechanical allodynia, or reductions in hippocampal parvalbumin expression in MIA offspring. MIA-associated changes in brain and behavior were likely driven by differences in milk nutritional values and not by direct exposure to LPS or inflammatory molecules as neither LPS binding protein nor interleukin-6 milk levels differed between groups. These findings reflected comparable microbiome and transcriptomic patterns at the genome-wide level. Animal models of early life stress can impact both parents and their offspring. One mechanism that can mediate the effects of such stressors is changes to maternal lactation quality which our data show can confer multifaceted and compounding effects on offspring physiology and behavior.

Epigenetic intersection of BDNF Val66Met genotype with premenstrual dysphoric disorder transcriptome in a cross-species model of estradiol add-back.

Premenstrual dysphoric disorder (PMDD) affects over 5% of women, with symptoms similar to anxiety and major depression, and is associated with differential sensitivity to circulating ovarian hormones. Little is known about the genetic and epigenetic factors that increase the risk to develop PMDD. We report that 17ß-estradiol (E2) affects the behavior and the epigenome in a mouse model carrying a single-nucleotide polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met), in a way that recapitulates the hallmarks of PMDD. Ovariectomized mice heterozygous for the BDNF Met allele (Het-Met) and their matched wild-type (WT) mice were administered estradiol or vehicle in drinking water for 6 weeks. Using the open field and the splash test, we show that E2 add-back induces anxiety-like and depression-like behavior in Het-Met mice, but not in WT mice. RNA-seq of the ventral hippocampus (vHpc) highlights that E2-dependent gene expression is markedly different between WT mice and Het-Met mice. Through a comparative whole-genome RNA-seq analysis between mouse vHpc and lymphoblastoid cell line cultures from control women and women with PMDD, we discovered common epigenetic biomarkers that transcend species and cell types. Those genes include epigenetic modifiers of the ESC/E(Z) complex, an effector of response to ovarian steroids. Although the BDNF Met genotype intersects the behavioral and transcriptional traits of women with PMDD, we suggest that these similarities speak to the epigenetic factors by which ovarian steroids produce negative behavioral effects.

Evidence for an imbalance between tau O-GlcNAcylation and phosphorylation in the hippocampus of a mouse model of Alzheimer's disease.

Intracellular accumulation of hyperphosphorylated tau protein is linked to neuronal degeneration in Alzheimer's disease (AD). Mounting evidence suggests that tau phosphorylation and O-N-acetylglucosamine glycosylation (O-GlcNAcylation) are mutually exclusive post-translational modifications. O-GlcNAcylation depends on 3-5% of intracellular glucose that enters the hexosamine biosynthetic pathway. To our knowledge, the existence of an imbalance between tau phosphorylation and O-GlcNAcylation has not been reported in animal models of AD, as yet. Here, we used triple transgenic (3xTg-AD) mice at 12 months, an age at which hyperphosphorylated tau is already detected and associated with cognitive decline. In these mice, we showed that tau was hyperphosphorylated on both Ser396 and Thr205 in the hippocampus, and to a lower extent and exclusively on Thr205 in the frontal cortex. Tau O-GlcNAcylation, assessed in tau immunoprecipitates, was substantially reduced in the hippocampus of 3xTg-AD mice, with no changes in the frontal cortex or in the cerebellum. No changes in the expression of the three major enzymes involved in O-GlcNAcylation, i.e., glutamine fructose-6-phosphate amidotransferase, O-linked ß-N-acetylglucosamine transferase, and O-GlcNAc hydrolase were found in the hippocampus of 3xTg-AD mice. These data demonstrate that an imbalance between tau phosphorylation and O-GlcNAcylation exists in AD mice, and strengthens the hypothesis that O-GlcNAcylation might be targeted by disease modifying drugs in AD.

Hedonic sensitivity to natural rewards is affected by prenatal stress in a sex-dependent manner.

Palatable food is a strong activator of the reward circuitry and may cause addictive behavior leading to eating disorders. How early life events and sex interact in shaping hedonic sensitivity to palatable food is largely unknown. We used prenatally restraint stressed (PRS) rats, which show abnormalities in the reward system and anxious/depressive-like behavior. Some of the hallmarks of PRS rats are known to be sex-dependent. We report that PRS enhanced and reduced milk chocolate-induced conditioned place preference in males and females, respectively. Male PRS rats also show increases in plasma dihydrotestosterone (DHT) levels and dopamine (DA) levels in the nucleus accumbens (NAc), and reductions in 5-hydroxytryptamine (5-HT) levels in the NAc and prefrontal cortex (PFC). In male rats, systemic treatment with the DHT-lowering drug finasteride reduced both milk chocolate preference and NAc DA levels. Female PRS rats showed lower plasma estradiol (E2 ) levels and lower DA levels in the NAc, and 5-HT levels in the NAc and PFC. E2 supplementation reversed the reduction in milk chocolate preference and PFC 5-HT levels. In the hypothalamus, PRS increased ERα and ERß estrogen receptor and CARTP (cocaine-and-amphetamine receptor transcript peptide) mRNA levels in males, and 5-HT2C receptor mRNA levels in females. Changes were corrected by treatments with finasteride and E2 , respectively. These new findings show that early life stress has a profound impact on hedonic sensitivity to high-palatable food via long-lasting changes in gonadal hormones. This paves the way to the development of hormonal strategies aimed at correcting abnormalities in the response to natural rewards.

Stress Response and Perinatal Reprogramming: Unraveling (Mal)adaptive Strategies.

Environmental stressors induce coping strategies in the majority of individuals. The stress response, involving the activation of the hypothalamic-pituitary-adrenocortical axis and the consequent release of corticosteroid hormones, is indeed aimed at promoting metabolic, functional, and behavioral adaptations. However, behavioral stress is also associated with fast and long-lasting neurochemical, structural, and behavioral changes, leading to long-term remodeling of glutamate transmission, and increased susceptibility to neuropsychiatric disorders. Of note, early-life events, both in utero and during the early postnatal life, trigger reprogramming of the stress response, which is often associated with loss of stress resilience and ensuing neurobehavioral (mal)adaptations. Indeed, adverse experiences in early life are known to induce long-term stress-related neuropsychiatric disorders in vulnerable individuals. Here, we discuss recent findings about stress remodeling of excitatory neurotransmission and brain morphology in animal models of behavioral stress. These changes are likely driven by epigenetic factors that lie at the core of the stress-response reprogramming in individuals with a history of perinatal stress. We propose that reprogramming mechanisms may underlie the reorganization of excitatory neurotransmission in the short- and long-term response to stressful stimuli.

The effects of antidepressant treatment in prenatally stressed rats support the glutamatergic hypothesis of stress-related disorders.

Abnormalities of synaptic transmission in the hippocampus represent an integral part of the altered programming triggered by early life stress, which enhances the vulnerability to stress-related disorders in the adult life. Rats exposed to prenatal restraint stress (PRS) develop enduring biochemical and behavioral changes characteristic of an anxious/depressive-like phenotype. Most neurochemical abnormalities in PRS rats are found in the ventral hippocampus, a region that encodes memories related to stress and emotions. We have recently demonstrated a causal link between the reduction of glutamate release in the ventral hippocampus and anxiety-like behavior in PRS rats. To confer pharmacological validity to the glutamatergic hypothesis of stress-related disorders, we examined whether chronic treatment with two antidepressants with different mechanisms of action could correct the defect in glutamate release and associated behavioral abnormalities in PRS rats. Adult unstressed or PRS rats were treated daily with either agomelatine (40 mg/kg, i.p.) or fluoxetine (5 mg/kg, i.p.) for 21 d. Both treatments reversed the reduction in depolarization-evoked glutamate release and in the expression of synaptic vesicle-associated proteins in the ventral hippocampus of PRS rats. Antidepressant treatment also corrected abnormalities in anxiety-/depression-like behavior and social memory performance in PRS rats. The effect on glutamate release was strongly correlated with the improvement of anxiety-like behavior and social memory. These data offer the pharmacological demonstration that glutamatergic hypofunction in the ventral hippocampus lies at the core of the pathological phenotype caused by early life stress and represents an attractive pharmacological target for novel therapeutic strategies.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research.

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Single-cell long-read sequencing-based mapping reveals specialized splicing patterns in developing and adult mouse and human brain.

RNA isoforms influence cell identity and function. However, a comprehensive brain isoform map was lacking. We analyze single-cell RNA isoforms across brain regions, cell subtypes, developmental time points and species. For 72% of genes, full-length isoform expression varies along one or more axes. Splicing, transcription start and polyadenylation sites vary strongly between cell types, influence protein architecture and associate with disease-linked variation. Additionally, neurotransmitter transport and synapse turnover genes harbor cell-type variability across anatomical regions. Regulation of cell-type-specific splicing is pronounced in the postnatal day 21-to-postnatal day 28 adolescent transition. Developmental isoform regulation is stronger than regional regulation for the same cell type. Cell-type-specific isoform regulation in mice is mostly maintained in the human hippocampus, allowing extrapolation to the human brain. Conversely, the human brain harbors additional cell-type specificity, suggesting gain-of-function isoforms. Together, this detailed single-cell atlas of full-length isoform regulation across development, anatomical regions and species reveals an unappreciated degree of isoform variability across multiple axes.

Anxiety-like behavior of prenatally stressed rats is associated with a selective reduction of glutamate release in the ventral hippocampus.

Abnormalities of synaptic transmission and plasticity in the hippocampus represent an integral part of the altered programming triggered by early life stress. Prenatally restraint stressed (PRS) rats develop long-lasting biochemical and behavioral changes, which are the expression of an anxious/depressive-like phenotype. We report here that PRS rats showed a selective impairment of depolarization- or kainate-stimulated glutamate and [(3)H]d-aspartate release in the ventral hippocampus, a region encoding memories related to stress and emotions. GABA release was unaffected in PRS rats. As a consequence of reduced glutamate release, PRS rats were also highly resistant to kainate-induced seizures. Abnormalities of glutamate release were associated with large reductions in the levels of synaptic vesicle-related proteins, such as VAMP (synaptobrevin), syntaxin-1, synaptophysin, synapsin Ia/b and IIa, munc-18, and Rab3A in the ventral hippocampus of PRS rats. Anxiety-like behavior in male PRS (and control) rats was inversely related to the extent of depolarization-evoked glutamate release in the ventral hippocampus. A causal relationship between anxiety-like behavior and reduction in glutamate release was demonstrated using a mixture of the mGlu2/3 receptor antagonist, LY341495, and the GABA(B) receptor antagonist, CGP52432, which was shown to amplify depolarization-evoked [(3)H]d-aspartate release in the ventral hippocampus. Bilateral microinfusion of CGP52432 plus LY341495 in the ventral hippocampus abolished anxiety-like behavior in PRS rats. These findings indicate that an impairment of glutamate release in the ventral hippocampus is a key component of the neuroplastic program induced by PRS, and that strategies aimed at enhancing glutamate release in the ventral hippocampus correct the "anxious phenotype" caused by early life stress.

Early life stress causes refractoriness to haloperidol-induced catalepsy.

The use of classic antipsychotic drugs is limited by the occurrence of extrapyramidal motor symptoms, which are caused by dopamine (DA) receptor blockade in the neostriatum. We examined the impact of early-life stress on haloperidol-induced catalepsy using the rat model of prenatal restraint stress (PRS). Adult "PRS rats," i.e., the offspring of mothers exposed to restraint stress during pregnancy, were resistant to catalepsy induced by haloperidol (0.5-5 mg/kg i.p.) or raclopride (2 mg/kg s.c.). Resistance to catalepsy in PRS rats did not depend on reductions in blood or striatal levels, as compared with unstressed control rats. PRS rats also showed a greater behavioral response to the DA receptor agonist, apomorphine, suggesting that PRS causes enduring neuroplastic changes in the basal ganglia motor circuit. To examine the activity of this circuit, we performed a stereological counting of c-Fos(+) neurons in the external and internal globus pallidus, subthalamic nucleus, and ventral motor thalamic nuclei. Remarkably, the number of c-Fos(+) neurons in ventral motor thalamic nuclei was higher in PRS rats than in unstressed controls, both under basal conditions and in response to single or repeated injections with haloperidol. Ventral motor thalamic nuclei contain exclusively excitatory projection neurons that convey the basal ganglia motor programming to the cerebral cortex. Hence, an increased activity of ventral motor thalamic nuclei nicely explains the refractoriness of PRS rats to haloperidol-induced catalepsy. Our data raise the interesting possibility that early-life stress is protective against extrapyramidal motor effects of antipsychotic drugs in the adult life.

Perspective on equitable translational studies and clinical support for an unbiased inclusion of the LGBTQIA2S+community.

Research regarding the mental health of the Lesbian, Gay, Bisexual, Transgender, Queer, Intersex, Asexual, 2 Spirit (LGBTQIA2S+) community has been historically biased by individual and structural homophobia, biphobia, and transphobia, resulting in research that does not represent the best quality science. Furthermore, much of this research does not serve the best interests or priorities of LGBTQIA2S + communities, despite significant mental health disparities and great need for quality mental health research and treatments in these populations. Here, we will highlight how bias has resulted in missed opportunities for advancing understanding of mental health within LGBTQIA2S + communities. We cite up-to-date research on mental health disparities facing the LGBTQIA2S + community and targeted treatment strategies, as well as guidance from health care professionals. Importantly, research is discussed from both preclinical and clinical perspectives, providing common language and research priorities from a translational perspective. Given the rising tide of anti-transgender sentiment among certain political factions, we further emphasize and discuss the impact of historical and present day ciscentrism and structural transphobia in transgender mental health research, from both clinical and translational perspectives, with suggestions for future directions to improve the quality of this field. Finally, we address current best practices for treatment of mental health issues in this community. This approach provides an opportunity to dispel myths regarding the LGBTQIA2S + community as well as inform the scientific community of best practices to work with this community in an equitable manner. Thus, our approach ties preclinical and clinical research within the LGBTQIA2S + community.

An allostatic epigenetic memory on chromatin footprints after double-hit acute stress.

Stress induces allostatic responses, whose limits depend on genetic background and the nature of the challenges. Allostatic load reflects the cumulation of these reponses over the course of life. Acute stress is usually associated with adaptive responses, although, depending on the intensity of the stress and individual differences , some may experience maladaptive coping that persists through life and may influence subsequent responses to stressful events, as is the case of post-traumatic stress disorder. We investigated the behavioral traits and epigenetic signatures in a double-hit mouse model of acute stress in which heterotypic stressors (acute swim stress and acute restraint stress) were applied within a 7-day interval period. The ventral hippocampus was isolated to study the footprints of chromatin accessibility driven by exposure to double-hit stress. Using ATAC sequencing to determine regions of open chromatin, we showed that depending on the number of acute stressors, several gene sets related to development, immune function, cell starvation, translation, the cytoskeleton, and DNA modification were reprogrammed in both males and females. Chromatin accessibility for transcription factor binding sites showed that stress altered the accessibility for androgen, glucocorticoid, and mineralocorticoid receptor binding sites (AREs/GREs) at the genome-wide level, with double-hit stressed mice displaying a profile unique from either single hit of acute stress. The investigation of AREs/GREs adjacent to gene coding regions revealed several stress-related genes, including Fkbp5, Zbtb16, and Ddc, whose chromatin accessibility was affected by prior exposure to stress. These data demonstrate that acute stress is not truly acute because it induces allostatic signatures that persist in the epigenome and may manifest when a second challenge hits later in life.

Milking It for All It's Worth: The Effects of Environmental Enrichment on Maternal Nurturance, Lactation Quality, and Offspring Social Behavior.

Breastfeeding confers robust benefits to offspring development in terms of growth, immunity, and neurophysiology. Similarly, improving environmental complexity, i.e., environmental enrichment (EE), contributes developmental advantages to both humans and laboratory animal models. However, the impact of environmental context on maternal care and milk quality has not been thoroughly evaluated, nor are the biological underpinnings of EE on offspring development understood. Here, Sprague Dawley rats were housed and bred in either EE or standard-housed (SD) conditions. EE dams gave birth to a larger number of pups, and litters were standardized and cross-fostered across groups on postnatal day (P)1. Maternal milk samples were then collected on P1 (transitional milk phase) and P10 (mature milk phase) for analysis. While EE dams spent less time nursing, postnatal enrichment exposure was associated with heavier offspring bodyweights. Milk from EE mothers had increased triglyceride levels, a greater microbiome diversity, and a significantly higher abundance of bacterial families related to bodyweight and energy metabolism. These differences reflected comparable transcriptomic changes at the genome-wide level. In addition to changes in lactational quality, we observed elevated levels of cannabinoid receptor 1 in the hypothalamus of EE dams, and sex-dependent and time-dependent effects of EE on offspring social behavior. Together, these results underscore the multidimensional impact of the combined neonatal and maternal environments on offspring development and maternal health. Moreover, they highlight potential deficiencies in the use of "gold standard" laboratory housing in the attempt to design translationally relevant animal models in biomedical research.

Genomic modules and intramodular network concordance in susceptible and resilient male mice across models of stress.

The multifactorial etiology of stress-related disorders necessitates a constant interrogation of the molecular convergences in preclinical models of stress that use disparate paradigms as stressors spanning from environmental challenges to genetic predisposition to hormonal signaling. Using RNA-sequencing, we investigated the genomic signatures in the ventral hippocampus common to mouse models of stress. Chronic oral corticosterone (CORT) induced increased anxiety- and depression-like behavior in wild-type male mice and male mice heterozygous for the gene coding for brain-derived neurotrophic factor Val66Met, a variant associated with genetic susceptibility to stress. In a separate set of male mice, chronic social defeat stress (CSDS) led to a susceptible or a resilient population, whose proportion was dependent on housing conditions, namely standard housing or enriched environment. Rank-rank-hypergeometric overlap (RRHO), a threshold-free approach that ranks genes by their p value and effect size direction, was used to identify genes from a continuous gradient of significancy that were concordant across groups. In mice treated with CORT and in standard-housed susceptible mice, differentially expressed genes (DEGs) were concordant for gene networks involved in neurotransmission, cytoskeleton function, and vascularization. Weighted gene co-expression analysis generated 54 gene hub modules and revealed two modules in which both CORT and CSDS-induced enrichment in DEGs, whose function was concordant with the RRHO predictions, and correlated with behavioral resilience or susceptibility. These data showed transcriptional concordance across models in which the stress coping depends upon hormonal, environmental, or genetic factors revealing common genomic drivers that embody the multifaceted nature of stress-related disorders.

Corticosterone induces discrete epigenetic signatures in the dorsal and ventral hippocampus that depend upon sex and genotype: focus on methylated Nr3c1 gene.

The genomic effects of circulating glucocorticoids are particularly relevant in cortico-limbic structures, which express a high concentration of steroid hormone receptors. To date, no studies have investigated genomic differences in hippocampal subregions, namely the dorsal (dHPC) and ventral (vHPC) hippocampus, in preclinical models treated with exogenous glucocorticoids. Chronic oral corticosterone (CORT) in mouse is a pharmacological approach that disrupts the activity of the hypothalamic-pituitary-adrenal axis, increases affective behavior, and induces genomic changes after stress in the HPC of wildtype (WT) mice and mice heterozygous for the gene coding for brain-derived neurotrophic factor Val66Met (hMet), a variant associated with genetic susceptibility to stress. Using RNA-sequencing, we investigated the genomic signatures of oral CORT in the dHPC and vHPC of WT and hMet male and female mice, and examined sex and genotype differences in response to oral CORT. Males under CORT showed lower glycemia and increased anxiety- and depression-like behavior compared to females that showed instead opposite affective behavior in response to CORT. Rank-rank-hypergeometric overlap (RRHO) was used to identify genes from a continuous gradient of significancy that were concordant across groups. RRHO showed that CORT-induced differentially expressed genes (DEGs) in WT mice and hMet mice converged in the dHPC of males and females, while in the vHPC, DEGs converged in males and diverged in females. The vHPC showed a higher number of DEGs compared to the dHPC and exhibited sex differences related to glucocorticoid receptor (GR)-binding genes and epigenetic modifiers. Methyl-DNA-immunoprecipitation in the vHPC revealed differential methylation of the exons 1C and 1F of the GR gene (Nr3c1) in hMet females. Together, we report behavioral and endocrinological sex differences in response to CORT, as well as epigenetic signatures that i) differ in the dHPC and vHPC,ii) are distinct in males and females, and iii) implicate differential methylation of Nr3c1 selectively in hMet females.

A spatially resolved brain region- and cell type-specific isoform atlas of the postnatal mouse brain.

Splicing varies across brain regions, but the single-cell resolution of regional variation is unclear. We present a single-cell investigation of differential isoform expression (DIE) between brain regions using single-cell long-read sequencing in mouse hippocampus and prefrontal cortex in 45 cell types at postnatal day 7 ( www.isoformAtlas.com ). Isoform tests for DIE show better performance than exon tests. We detect hundreds of DIE events traceable to cell types, often corresponding to functionally distinct protein isoforms. Mostly, one cell type is responsible for brain-region specific DIE. However, for fewer genes, multiple cell types influence DIE. Thus, regional identity can, although rarely, override cell-type specificity. Cell types indigenous to one anatomic structure display distinctive DIE, e.g. the choroid plexus epithelium manifests distinct transcription-start-site usage. Spatial transcriptomics and long-read sequencing yield a spatially resolved splicing map. Our methods quantify isoform expression with cell-type and spatial resolution and it contributes to further our understanding of how the brain integrates molecular and cellular complexity.

Environmental epigenetics of sex differences in the brain.

Experiences throughout the life course lead to unique phenotypes even among those with the same genotype. Genotype sets the substrate on which physiologic processes, which communicate with the brain, mediate the effects of life experiences via epigenetics. Epigenetics modify the expression of genes in the brain and body in response to circulating hormones and other mediators, which are activated to facilitate survival responses through a process called allostasis. Epigenetic signatures can even be inherited, resulting in transgenerational effects. This chapter addresses epigenetics in the context of sex differences, discussing the intersection between genetics and gonadal hormones and their effect in the brain at discrete developmental periods.

Maternal stress programs accelerated aging of the basal ganglia motor system in offspring.

Early-life stress involved in the programming of stress-related illnesses can have a toxic influence on the functioning of the nigrostriatal motor system during aging. We examined the effects of perinatal stress (PRS) on the neurochemical, electrophysiological, histological, neuroimaging, and behavioral correlates of striatal motor function in adult (4 months of age) and old (21 months of age) male rats. Adult PRS offspring rats showed reduced dopamine (DA) release in the striatum associated with reductions in tyrosine hydroxylase-positive (TH+) cells and DA transporter (DAT) levels, with no loss of striatal dopaminergic terminals as assessed by positron emission tomography analysis with fluorine-18-l-dihydroxyphenylalanine. Striatal levels of DA and its metabolites were increased in PRS rats. In contrast, D2 DA receptor signaling was reduced and A2A adenosine receptor signaling was increased in the striatum of adult PRS rats. This indicated enhanced activity of the indirect pathway of the basal ganglia motor circuit. Adult PRS rats also showed poorer performance in the grip strength test and motor learning tasks. The aged PRS rats also showed a persistent reduction in striatal DA release and defective motor skills in the pasta matrix and ladder rung walking tests. In addition, the old rats showed large increases in the levels of SNAP-25 and synaptophysin, which are synaptic vesicle-related proteins in the striatum, and in the PRS group only, reductions in Syntaxin-1 and Rab3a protein levels were observed. Our findings indicated that the age-dependent threshold for motor dysfunction was lowered in PRS rats. This area of research is underdeveloped, and our study suggests that early-life stress can contribute to an increased understanding of how aging diseases are programmed in early-life.