Prenatal stress on the kinetic properties of Ca2+ and K+ channels in offspring hippocampal CA3 pyramidal neurons

Neural correlates of disaster-related prenatal maternal stress in young adults from Project Ice Storm: Focus on amygdala, hippocampus, and prefrontal cortex

Background

Studies have shown that prenatal maternal stress alters volumes of the amygdala and hippocampus, and alters functional connectivity between the amygdala and prefrontal cortex. However, it remains unclear whether prenatal maternal stress (PNMS) affects volumes and functional connectivity of these structures at their subdivision levels.

Methods

T1-weighted MRI and resting-state functional MRI were obtained from 19-year-old young adult offspring with (n = 39, 18 male) and without (n = 65, 30 male) exposure to PNMS deriving from the 1998 ice storm. Volumes of amygdala nuclei, hippocampal subfields and prefrontal subregions were computed, and seed-to-seed functional connectivity analyses were conducted.

Results

Compared to controls, young adult offspring exposed to disaster-related PNMS had larger volumes of bilateral whole amygdala, driven by the lateral, basal, central, medial, cortical, accessory basal nuclei, and corticoamygdaloid transition; larger volumes of bilateral whole hippocampus, driven by the CA1, HATA, molecular layer, fissure, tail, CA3, CA4, and DG; and larger volume of the prefrontal cortex, driven by the left superior frontal. Inversely, young adult offspring exposed to disaster-related PNMS had lower functional connectivity between the whole amygdala and the prefrontal cortex (driven by bilateral frontal poles, the left superior frontal and left caudal middle frontal); and lower functional connectivity between the hippocampal tail and the prefrontal cortex (driven by the left lateral orbitofrontal).

Conclusion

These results suggest the possibility that effects of disaster-related PNMS on structure and function of subdivisions of offspring amygdala, hippocampus and prefrontal cortex could persist into young adulthood.

Sex differences in the vulnerability of the hippocampus to prenatal stress

Distressing events during pregnancy that engage activity of the body's endocrine stress response have been linked with later life cognitive deficits in offspring and associated with developmental changes in cognitive-controlling neural regions. Interestingly, prenatal stress (PS)-induced alterations have shown some sex specificity. Here, we review the literature of animal studies examining sex-specific effect of physical PS on the function and structure of the hippocampus as hippocampal impairments likely underlie PS-associated deficits in learning and memory. Furthermore, the connectivity between the hypothalamic-pituitary-adrenal (HPA) axis and the hippocampus as well as the heavy presence of glucocorticoid receptors (GRs) in the hippocampus suggests this structure plays an important role in modulation of activity within stress circuitry in a sex-specific pattern. We hope that better understanding of sex-specific, PS-related hippocampal impairment will assist in uncovering the molecular mechanisms behind sex-based risk factors in PS populations across development, and perhaps contribute to greater precision in management of cognitive disturbances in this vulnerable population.

Involvement of SNARE complex in the hippocampus and prefrontal cortex of offspring with depression induced by prenatal stress

BACKGROUND

Prenatal stress (PS) exposure can cause depression-like behavior in offspring, and maladaptive responses including physiological and neurobiological changes. Glutamate neurotransmission is implicated in effects of PS and in antidepressant mechanisms; however, the mechanisms underlying its involvement remain unclear. In the synapse, the formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex is essential for vesicular docking and neurotransmitter release.

METHODS

To explore effects of PS on the SNARE complex, pregnant rats were assigned to a control or PS group. Both male and female offspring in each group were used in this study. PS rats were exposed to restraint stress three times daily for 45 min on days 14-20 of pregnancy.

RESULTS

In the PS offspring, the expression of the SNARE protein SNAP-25, vesicle-associated membrane protein (VAMP)-2, and Syntaxin 1a was significantly increased in the hippocampus and prefrontal cortex. These observations were associated with increased levels of proteins that chaperone SNARE complex formation, including Munc-18, α-synuclein, CSPα, complexin1, and complexin2. Immunoblotting of hippocampal and prefrontal cortex homogenates revealed significantly increased SNARE complex formation. vGluT1 protein expression was also significantly increased in the offspring. Additionally, PS was associated with increased mRNA expression of VAMP1, VAMP2, SNAP25, Syntaxin1a, and Syntaxin1b in the hippocampus and prefrontal cortex. Increased monomeric SNARE proteins, SNARE complex formation, vesicle-associated proteins, and vGluT1 may explain the increase in glutamate and its downstream excitotoxicity.

CONCLUSIONS

These results support the hypothesis that glutamate release and vesicular glutamate transporters play a role in PS-induced depression-like behavior of rat offspring.

Maternal administration of magnesium sulfate promotes cell proliferation in hippocampus dentate gyrus in offspring mice after exposing to prenatal stress

Prenatal stress (PS) inhibits cell proliferation in the hippocampal dentate gyrus (DG), which is related to hippocampal anatomy and function abnormality. The aim of the study was to investigate the effects of magnesium sulfate (MgSO₄) on PS-induced cell proliferation suppression in offspring during embryonic stage and postnatal spatial learning. MgSO₄ administration was performed after PS treatment on pregnant mice. Mice were randomly divided into four groups: non-PS or PS maternal mice injected with MgSO₄ or saline (P+NS, P+MG, C+MG and C+NS group). Corticosterone was collected from amniotic fluid of mother mice on day 17 of embryonic stage (E17). The ability for spatial learning and memory of pups postnatal 3 week was evaluated using water maze assay. Additionally, cell proliferation was detected by assessing the expression of Ki67 using immunohistochemistry in mice fetuses or pups. PS significantly increased corticosterone level in amniotic fluid (P<0.05) and impaired the spatial learning and memory (P+NS vs C+NS of latency time and track path length: P<0.05) of offspring on postnatal day 21. However, MgSO₄ administration could reverse PS-induced spatial learning and memory disability (P+MG vs P+NS, P<0.05). Additionally, PS reduced the number of Ki67-positive cell in hippocampal DG on E17, E19 and postnatal day 21 (P+NS vs C+NS, P<0.05), which were also abrogated by maternal administration of MgSO₄ (P+MG vs P+NS, P<0.05). Collectively, prenatal administration of MgSO₄ can reverse PS-induced reduction of cell proliferation in hippocampal DG during embryonic stage and postnatal spatial learning.

Behavior genetics and postgenomics

The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. According to three widely held dogmas, DNA is the unchanging template of heredity, is identical in all the cells and tissues of the body, and is the sole agent of inheritance. Rather than being an unchanging template, DNA appears subject to a good deal of environmentally induced change. Instead of identical DNA in all the cells of the body, somatic mosaicism appears to be the normal human condition. And DNA can no longer be considered the sole agent of inheritance. We now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, epigenetic regulation, DNA variability, and somatic mosaicism appear to be particularly prevalent in the human brain and probably are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period and, in particular, in enabling phenotypic plasticity in offspring. I examine one of the central claims to emerge from the use of heritability studies in the behavioral sciences, the principle of minimal shared maternal effects, in light of the growing awareness that the maternal perinatal environment is a critical venue for the exercise of adaptive phenotypic plasticity. This consideration has important implications for both developmental and evolutionary biology.

Repeated carbenoxolone injections during late pregnancy alter Snk-SPAR and PSD-95 expression in the hippocampus of rat pups

Homeostasis of circulating cortisol is maintained by the 11β-HSD2 enzyme which inactivates cortisol into cortisone. It is abundantly expressed in the placenta where it protects the fetus from high levels of maternal glucocorticoids (GCs). Maternal administration of Carbenoxolone (Cbx), a powerful 11β-HSD2 inhibitor, leads to an increase in fetal cortisol. Previous data showed that intrauterine environment plays a crucial role in determining hippocampal structure and function. Exposure of pregnant rats to high levels of GC leads to low birth weight in offspring and an increased risk of age related memory and cognitive deficits later in life. Glutamate receptors are localized in the postsynaptic density (PSD), where many signaling proteins, cytoskeleton proteins, and ion channels are found. Any change in the number of these molecules can influence the morphology and function of the dendritic spine. We proposed that repeated Cbx injections during late pregnancy may alter the scaffolding proteins of the NMDA receptor in the pup's brain. We investigated the effects of repeated maternal Cbx injections on the scaffolding proteins of NMDA receptor in the hippocampus of rat pups. We showed that injecting pregnant rats with Cbx injections (30mg/kg) during GD 14-21 leads to a significant decrease in SPAR (Spine Associated Rap Guanylate kinase activating protein) (p<0.001) and PSD-95 (p<0.05) but a significant increase in Snk (Serum inducible kinase) (p<0.001) in the pup's hippocampus at P40. In general, Snk is induced by neuronal activity and plays an important role in phosphorylating SPAR. The phosphorylated SPAR is then recognized and degraded by ubiquitin proteasome system (UPS), causing the depletion of SPAR and PSD-95 from the spines. The results suggest that fetal exposure to excessive GC levels may activate the Snk/SPAR pathway and lead to the depletion of SPAR and PSD-95. Since GCs drugs are commonly used in various obstetric and pediatric conditions, it is important to consider the risks and benefits of prenatal GCs exposure in order to prevent neurodevelopmental delay in the offspring.

Prenatal stress causes dendritic atrophy of pyramidal neurons in hippocampal CA3 region by glutamate in offspring rats

A substantial number of human epidemiological data, as well as experimental studies, suggest that adverse maternal stress during gestation is involved in abnormal behavior, mental, and cognition disorder in offspring. To explore the effect of prenatal stress (PS) on hippocampal neurons, in this study, we observed the dendritic field of pyramidal neurons in hippocampal CA3, examined the concentration of glutamate (Glu), and detected the expression of synaptotagmin-1 (Syt-1) and N-methyl-D-aspartate receptor 1 (NR1) in hippocampus of juvenile female offspring rats. Pregnant rats were divided into two groups: control group (CON) and PS group. Female offspring rats used were 30-day old. The total length of the apical dendrites of pyramidal neurons in hippocampal CA3 of offspring was significantly shorter in PS than that in CON (p < 0.01). The number of branch points of the apical dendrites of pyramidal neurons in hippocampal CA3 of offspring was significantly less in PS (p < 0.01). PS offspring had a higher concentration of hippocampal Glu compared with CON (p < 0.05). PS offspring displayed increased expression of Syt-1 and decreased NR1 in hippocampus compared with CON (p < 0.001 and p < 0.01, respectively). The expression of NR1 in different hippocampus subfields of offspring was significantly decreased in PS than that in CON (p < 0.05-0.01). This study shows that PS increases the Glu in hippocampus and causes apical dendritic atrophy of pyramidal neurons of hippocampal CA3 in offspring rats. The decline of NR1 in hippocampus may be an adaptive response to the increased Glu.

A milk-based wolfberry preparation prevents prenatal stress-induced cognitive impairment of offspring rats, and inhibits oxidative damage and mitochondrial dysfunction in vitro

Lycium barbarum (Fructus Lycii, Wolfberry, or Gouqi) belongs to the Solanaceae. The red-colored fruits of L. barbarum have been used for a long time as an ingredient in Chinese cuisine and brewing, and also in traditional Chinese herbal medicine for improving health. However, its effects on cognitive function have not been well studied. In the present study, prevention of a milk-based wolfberry preparation (WP) on cognitive dysfunction was tested in a prenatal stress model with rats and the antioxidant mechanism was tested by in vitro experiments. We found that prenatal stress caused a significant decrease in cognitive function (Morris water maze test) in female offspring. Pretreatment of the mother rats with WP significantly prevented the prenatal stress-induced cognitive dysfunction. In vitro studies showed that WP dose-dependently scavenged hydroxyl and superoxide radicals (determined by an electron spin resonance spectrometric assay), and inhibited FeCl(2)/ascorbic acid-induced dysfunction in brain tissue and tissue mitochondria, including increases in reactive oxygen species and lipid peroxidation and decreases in the activities of complex I, complex II, and glutamate cysteine ligase. These results suggest that dietary supplementation with WP may be an effective strategy for preventing the brain oxidative mitochondrial damage and cognitive dysfunction associated with prenatal stress.

Prenatal stress alters spine density and dendritic length of nucleus accumbens and hippocampus neurons in rat offspring

Prenatal stress alters neuronal morphology of mesocorticolimbic structures such as frontal cortex and hippocampus in the adult offspring. We investigated here the effects of prenatal stress on the spine density and the dendrite morphology of hippocampal pyramidal neurons and medium spiny cells from nucleus accumbens in prepubertal and adult male offsprings. Sprague-Dawley pregnant dams were stressed by restraining movement daily for 2 hours from gestational day 11 until delivery. Control mothers remained free in their home cage without water and food during the stressful event. Male offsprings from immobilized and control rats were left to grow until postnatal day (PD) 35 for the prepubertal group, and until PD 65 for the adult group. Spontaneous locomotor activity was assessed and then brains were removed to study the dendritic morphology by the Golgi-Cox stain method followed by Sholl analysis. Prenatally stressed animals demonstrated increased locomotion and alterations in spine density in the hippocampus and nucleus accumbens at both ages. However, prepubertal males showed an increase in spine density in the CA1 hippocampus with a decrease in CA3 hippocampus, whereas the adult group showed a decrease in the spine density in both of the regions studied. These results suggest that prenatal stress carried out during the middle of pregnancy affect the spine density and basal dendrites of pyramidal neurons of hippocampus, as well as the dendritic morphology of nucleus accumbens which may reflect important changes in the mesocorticolimbic dopaminergic transmission and behaviors associated with the development of psychiatric diseases such as schizophrenia.