Postnatal Choline Supplementation Rescues Deficits in Synaptic Plasticity Following Prenatal Ethanol Exposure.

Prenatal ethanol exposure (PNEE) is a leading cause of neurodevelopmental impairments, yet treatments for individuals with PNEE are limited. Importantly, postnatal supplementation with the essential nutrient choline can attenuate some adverse effects of PNEE on cognitive development; however, the mechanisms of action for choline supplementation remain unclear. This study used an animal model to determine if choline supplementation could restore hippocampal synaptic plasticity that is normally impaired by prenatal alcohol. Throughout gestation, pregnant Sprague Dawley rats were fed an ethanol liquid diet (35.5% ethanol-derived calories). Offspring were injected with choline chloride (100 mg/kg/day) from postnatal days (PD) 10-30, and then used for in vitro electrophysiology experiments as juveniles (PD 31-35). High-frequency conditioning stimuli were used to induce long-term potentiation (LTP) in the medial perforant path input to the dentate gyrus of the hippocampus. PNEE altered synaptic transmission in female offspring by increasing excitability, an effect that was mitigated with choline supplementation. In contrast, PNEE juvenile males had decreased LTP compared to controls, and this was rescued by choline supplementation. These data demonstrate sex-specific changes in plasticity following PNEE, and provide evidence that choline-related improvements in cognitive functioning may be due to its positive impact on hippocampal synaptic physiology.

Effects of prenatal ethanol exposure on choline-induced long-term depression in the hippocampus.

Choline is an essential nutrient under evaluation as a cognitive enhancing treatment for fetal alcohol spectrum disorders (FASD) in clinical trials. As a result, there is increased pressure to identify therapeutic mechanism(s) of action. Choline is not only a precursor for several essential cell membrane components and signaling molecules but also has the potential to directly affect synaptic mechanisms that are believed important for cognitive processes. In the current work, we study how the direct application of choline can affect synaptic transmission in the dentate gyrus (DG) of hippocampal slices obtained from adolescent (postnatal days 21-28) Sprague-Dawley rats (Rattus norvegicus). The acute administration of choline chloride (2 mM) reliably induced a long-term depression (LTD) of field excitatory postsynaptic potentials (fEPSPs) in the DG in vitro. The depression required the involvement of M1 receptors, and the magnitude of the effect was similar in slices obtained from male and female animals. To further study the impact of choline in an animal model of FASD, we examined offspring from dams fed an ethanol-containing diet (35.5% ethanol-derived calories) throughout gestation. In slices from the adolescent animals that experienced prenatal ethanol exposure (PNEE), we found that the choline induced an LTD that uniquely involved the activation of N-methyl-d-aspartate (NMDA) and M1 receptors. This study provides a novel insight into how choline can modulate hippocampal transmission at the level of the synapse and that it can have unique effects following PNEE.NEW & NOTEWORTHY Choline supplementation is a nutraceutical therapy with significant potential for a variety of developmental disorders; however, the mechanisms involved in its therapeutic effects remain poorly understood. Our research shows that choline directly impacts synaptic communication in the brain, inducing a long-term depression of synaptic efficacy in brain slices. The depression is equivalent in male and female animals, involves M1 receptors in control animals, but uniquely involves NMDA receptors in a model of FASD.

ISX-9 can potentiate cell proliferation and neuronal commitment in the rat dentate gyrus.

Adult hippocampal neurogenesis can be modulated by various physiological and pathological conditions, including stress, affective disorders, and several neurological conditions. Given the proposed role of this form of structural plasticity in the functioning of the hippocampus (namely learning and memory and affective behaviors), it is believed that alterations in hippocampal neurogenesis might underlie some of the behavioral deficits associated with these psychiatric and neurological conditions. Thus, the search for compounds that can reverse these deficits with minimal side effects has become a recognized priority. In the present study we tested the pro-neurogenic effects of isoxazole 9 (Isx-9), a small synthetic molecule that has been recently identified through the screening of chemical libraries in stem cell-based assays. We found that administration of Isx-9 for 14days was able to potentiate cell proliferation and increase the number of immature neurons in the hippocampal DG of adult rats. In addition, Isx-9 treatment was able to completely reverse the marked reduction in these initial stages of the neurogenic process observed in vehicle-treated animals (which were submitted to repeated handling and exposure to daily intraperitoneal injections). Based on these results, we recommend that future neurogenesis studies that require repeated handling and manipulation of animals should include a naïve (non-manipulated) control to determine the baseline levels of hippocampal cell proliferation and neuronal differentiation. Overall, these findings demonstrate that Isx-9 is a promising synthetic compound for the mitigation of stress-induced deficits in adult hippocampal neurogenesis. Future studies are thus warranted to evaluate the pro-neurogenic properties of Isx-9 in animal models of affective and neurological disorders associated with impaired hippocampal structural plasticity.

Omega-3 fatty acids can reverse the long-term deficits in hippocampal synaptic plasticity caused by prenatal ethanol exposure.

Fetal alcohol spectrum disorders result in long-lasting neurological deficits including decreases in synaptic plasticity and deficits in learning and memory. In this study we examined the effects of prenatal ethanol exposure on hippocampal synaptic plasticity in male and female Sprague-Dawley rats. Furthermore, we looked at the capacity for postnatal dietary intervention to rescue deficits in synaptic plasticity. Animals were fed an omega-3 enriched diet from birth until adulthood (PND55-70) and in vivo electrophysiology was performed by stimulating the medial perforant path input to the dentate gyrus and recording field excitatory post-synaptic potentials. LTP was induced by administering bursts of five 400 Hz pulses as a theta-patterned train of stimuli (200 ms inter-burst interval). Ethanol-exposed adult males, but not females, exhibited a significant reduction in LTP. This deficit in male animals was completely reversed with an omega-3 enriched diet. These results demonstrate that omega-3 fatty acids can have benefits following prenatal neuropathological insults and may be a viable option for alleviating some of the neurological deficits associated with FASD.

Omega-3 supplementation can restore glutathione levels and prevent oxidative damage caused by prenatal ethanol exposure.

Prenatal ethanol exposure (PNEE) causes long-lasting deficits in brain structure and function. In this study, we have examined the effect of PNEE on antioxidant capacity and oxidative stress in the adult brain with particular focus on four brain regions known to be affected by ethanol: cerebellum, prefrontal cortex and hippocampus (cornu ammonis and dentate gyrus subregions). We have utilized a liquid diet model of fetal alcohol spectrum disorders that is supplied to pregnant Sprague-Dawley rats throughout gestation. To examine the therapeutic potential of omega-3 fatty acid supplementation, a subset of animals were provided with an omega-3-enriched diet from birth until adulthood to examine whether these fatty acids could ameliorate any deficits in antioxidant capacity that occurred due to PNEE. Our results showed that PNEE caused a long-lasting decrease in glutathione levels in all four brain regions analyzed that was accompanied by an increase in lipid peroxidation, a marker of oxidative damage. These results indicate that PNEE induces long-lasting changes in the antioxidant capacity of the brain, and this can lead to a state of oxidative stress. Postnatal omega-3 supplementation was able to increase glutathione levels and reduce lipid peroxidation in PNEE animals, partially reversing the effects of alcohol exposure, particularly in the dentate gyrus and the cerebellum. This is the first study where omega-3 supplementation has been shown to have a beneficial effect in PNEE, reducing oxidative stress and enhancing antioxidant capacity.

Glutathione restores the mechanism of synaptic plasticity in aged mice to that of the adult.

Glutathione (GSH), the major endogenous antioxidant produced by cells, can modulate the activity of N-methyl-D-aspartate receptors (NMDARs) through its reducing functions. During aging, an increase in oxidative stress leads to decreased levels of GSH in the brain. Concurrently, aging is characterized by calcium dysregulation, thought to underlie impairments in hippocampal NMDAR-dependent long-term potentiation (LTP), a form of synaptic plasticity thought to represent a cellular model for memory. Here we show that orally supplementing aged mice with N-acetylcysteine, a precursor for the formation of glutathione, reverses the L-type calcium channel-dependent LTP seen in aged animals to NMDAR-dependent LTP. In addition, introducing glutathione in the intrapipette solution during whole-cell recordings restores LTP obtained in whole-cell conditions in the aged hippocampus. We conclude that aging leads to a reduced redox potential in hippocampal neurons, triggering impairments in LTP.