Amelioration of prenatal alcohol effects by environmental enrichment in a mouse model of FASD

Maternal alcohol consumption during pregnancy results in a spectrum of behavioural and cognitive deficits collectively known as Fetal Alcohol Spectrum Disorders (FASD). Currently, little is know about if and how the external environment may modulate these deficits. I have used C57BL/6 mice to study this interaction between prenatal alcohol exposure and the postnatal environment. Alcohol exposure during synaptogenesis produces high levels of anxiety-like traits and decreased memory performance. Alcohol-exposed mice (and matched unexposed controls) were put in \u27environmentally-enriched\u27 conditions of voluntary exercise, physical activities and cognitive stimulation to ascertain the effects of a positive postnatal environment. The results show that environmental enrichment ameliorates anxiety-like behaviour and memory deficits of alcohol-exposed mice. However this recovery is incomplete, indicative of the long-lasting, potentially permanent damage of prenatal alcohol exposure on the developing brain. In follow-up studies, I have uncovered gene expression changes in the hippocampus that are associated with behavioural and cognitive amelioration. To accomplish this, I have used mouse hippocampal RNA for microarray and RNA-Seq. My results have identified several key genes and molecular pathways that are associated with synaptic and structural plasticity, neurogenesis, long-term potentiation and angiogenesis. The behavioural and molecular results of this project represent a novel finding in the field of FASD research. The genes and pathways uncovered provide a possible explanation to understand FASD. They are also potential targets when formulating behavioural and pharmacological rehabilitative therapies

Linking cortical inhibitory circuit dysfunction and psychiatric disease

Inhibitory interneurons make up approximately 10% of all cortical neurons, but they are critical for normal circuit functioning, as evidenced by the role of inhibitory dysfunction in a number of neurological and psychiatric diseases. In this dissertation, I show multiple examples of the role of inhibitory perturbations causing circuit dysfunction and abnormal behavior in models of psychiatric disease. In Chapter 1, I characterize behavioral abnormalities in a loss of function model of a high confidence autism gene, link these to changes in long-range communication between the prefrontal cortex and ventral hippocampus, and show deficits in inhibitory signaling related to these long-range deficits. In Chapter 2, I characterize the response of VIP interneurons to cholinergic stimulation and show this is altered in both genetic and environmental models of autism. In Chapter 3, I demonstrate how VIP interneuron signaling regulates prefrontal cortex-ventral hippocampal synchrony in order to properly regulate anxiety behavior. Together, these studies show how critical proper inhibitory signaling is to normal prefrontal cortex processing, and how disruptions in this signaling can give rise to disease states

Ethanol exposure during synaptogenesis in a mouse model of fetal alcohol spectrum disorders: acute and long-term effects on gene expression and behaviour

Alcohol is a neuroactive molecule that is able to exert variable and often detrimental effects on the developing brain, resulting in a broad range of physiological, behavioural, and cognitive phenotypes that characterize ‘fetal alcohol spectrum disorders’ (FASD). Factors affecting the manifestation of these phenotypes include alcohol dosage, timing of exposure, and pattern of maternal alcohol consumption; however, the biological processes that are vulnerable to ethanol at any given neurodevelopmental stage are unclear, as is how their disruption results in the emergence of specific pathological phenotypes later in life. The research included in this thesis utilizes a C57BL/6J (B6) mouse model to examine the changes to gene expression and behaviour following a binge-like exposure to ethanol during synaptogenesis, a period of neurodevelopment characterized by the rapid formation and pruning of synaptic connectivity that correlates to brain development during the human third trimester. B6 pups were treated with a high dose (5 g/kg over 2 hours) of ethanol at postnatal day 4 (P4), P7, or on both days (P4+7). Mice were evaluated using a battery of behavioural tests designed to assess FASD-relevant phenotypes, and showed delayed achievement of neuromuscular coordination, hyperactivity, increased anxiety-related traits, and impaired spatial learning and memory. Gene expression analysis identified 315 transcripts that were altered acutely (4 hours) following ethanol exposure. Up-regulated transcripts were associated with cellular stress response, including both pro- and anti-apoptotic molecules, as well as maintenance of cell structural integrity. Down-regulated transcripts were associated with energetically costly processes such as ribosome biogenesis and cell cycle progression. Genes critical to synapse formation were also affected, as well as genes important for the appropriate development of the hypothalamic-pituitary-adrenal axis. Additionally, gene expression changes within the adult brain of mice treated with ethanol at P4+7 were examined to evaluate the long-term effects of neurodevelopmental alcohol exposure. Array analysis identified 376 altered mRNA transcripts with roles in synaptic function, plasticity, and stability, as well as epigenetic processes such as folate metabolism and chromatin remodeling. MicroRNA analyses identified changes in the levels of 33 microRNA species, suggesting that that long-term changes to gene expression following may be maintained (at least in part) via epigenetic mechanisms. Taken together, these analyses illustrate the sensitivity of synaptogenesis to ethanol exposure, leading to a ‘molecular footprint’ of gene expression changes that persists into adulthood and may contribute to the emergence of long-term behavioural and cognitive phenotypes associated with FASD

Anxiety-related activity of ventral hippocampal interneurons.

Anxiety is an aversive mood reflecting the anticipation of potential threats. The ventral hippocampus (vH) is a key brain region involved in the genesis of anxiety responses. Recent studies have shown that anxiety is mediated by the activation of vH pyramidal neurons targeting various limbic structures. Throughout the cortex, the activity of pyramidal neurons is controlled by GABA-releasing inhibitory interneurons and the GABAergic system represents an important target of anxiolytic drugs. However, how the activity of vH inhibitory interneurons is related to different anxiety behaviours has not been investigated so far. Here, we integratedin vivoelectrophysiology with behavioural phenotyping of distinct anxiety exploration behaviours in rats. We showed that pyramidal neurons and interneurons of the vH are selectively active when animals explore specific compartments of the elevated-plus-maze (EPM), an anxiety task for rodents. Moreover, rats with prior goal-related experience exhibited low-anxiety exploratory behaviour and showed a larger trajectory-related activity of vH interneurons during EPM exploration compared to high anxiety rats. Finally, in low anxiety rats, trajectory-related vH interneurons exhibited opposite activity to pyramidal neurons specifically in the open arms (i.e. more anxiogenic) of the EPM. Our results suggest that vH inhibitory micro-circuits could act as critical elements underlying different anxiety states

Erythropoietin enhances hippocampal long-term potentiation and memory

<p>Abstract</p> <p>Background</p> <p>Erythropoietin (EPO) improves cognition of human subjects in the clinical setting by as yet unknown mechanisms. We developed a mouse model of robust cognitive improvement by EPO to obtain the first clues of how EPO influences cognition, and how it may act on hippocampal neurons to modulate plasticity.</p> <p>Results</p> <p>We show here that a 3-week treatment of young mice with EPO enhances long-term potentiation (LTP), a cellular correlate of learning processes in the CA1 region of the hippocampus. This treatment concomitantly alters short-term synaptic plasticity and synaptic transmission, shifting the balance of excitatory and inhibitory activity. These effects are accompanied by an improvement of hippocampus dependent memory, persisting for 3 weeks after termination of EPO injections, and are independent of changes in hematocrit. Networks of EPO-treated primary hippocampal neurons develop lower overall spiking activity but enhanced bursting in discrete neuronal assemblies. At the level of developing single neurons, EPO treatment reduces the typical increase in excitatory synaptic transmission without changing the number of synaptic boutons, consistent with prolonged functional silencing of synapses.</p> <p>Conclusion</p> <p>We conclude that EPO improves hippocampus dependent memory by modulating plasticity, synaptic connectivity and activity of memory-related neuronal networks. These mechanisms of action of EPO have to be further exploited for treating neuropsychiatric diseases.</p

La primera entrada en el laberinto en cruz elevado como predictor del nivel de ansiedad

RESUMEN Introducción: Generalmente el análisis del comportamiento exploratorio de ratas en laberinto en cruz elevado es realizado a la población general sin llevarse a cabo ningún tipo de discriminación entre individuos en función de sus decisiones exploratorias. Considerando la toma de decisiones para entrar a una zona del laberinto como un conflicto entre motivación de explorar y aversión,  el presente trabajo pretende evaluar la primera entrada a los brazos del laberinto como indicador del estado inicial de los niveles de motivación y aversión del entorno y en consecuencia, como indicador temprano de la evolución del comportamiento exploratorio.Materiales y métodos: Se evaluó el desempeño de ratas Wistar machos en laberinto en cruz elevado sometidas a una primera exposición, separándolas en dos grupos, de acuerdo a si su primera entrada fue en los brazos abiertos o en los brazos cerrados.Resultados: Aquellas ratas que primero entraron en los brazos abiertos obtuvieron valores significativamente mayores para el número de entradas y tiempo de permanencia en estos brazos en comparación con aquellas que entraron primero a los brazos cerrados; mientras que no se evidenció diferencias en el número de entradas en los brazos cerrados.Conclusión: La primera decisión del animal resulta predictiva del comportamiento durante los 5 minutos de exploración y permite discriminar las ratas entre dos niveles de ansiedad, sugiriéndose como variable discriminatoria el porcentaje de entradas a los brazos abiertos con punto de corte en 30,77%. Salud UIS 2010; 42:   Palabras clave: Aversión, comportamiento exploratorio, motivación, toma de decisión, ratas Wistar   ABSTRACT Introduction: Usually, the analysis of the rat exploratory behavior in elevated plus maze is carried out to the general population, without any discrimination between individuals as a function of their exploratory decisions. Considering the decision making to enter into a maze zone as a conflict between motivation to explore and aversion, the current work pretends to assess the first entry into the maze arms as indicator of the initial state of the motivation and aversion levels of the environment and therefore, as early indicator of the evolution of the exploratory behavior.Materials and methods: It was evaluated  the performance of male Wistar rats in elevated plus maze subjected to a first exposure, divided into two groups, according to whether its first entry was made into the open or closed arms.Results: Those rats that entered first into the open arms obtained higher significant values in the number of entries and time spent in these arms with respect to those rats that entered first into the closed arms; but it was not obtained differences in the number of entries into the closed arms.Conclusion: The first animal choice predicts the behavior during the 5 minutes of exploration and allows to discriminate the rats between two anxiety levels, being suggested the percentage of entries in open arms as discriminatory variable with cut-off value in 30.77%. Salud UIS 2010; 42:   Keywords: Aversion, decision making, exploratory behavior, motivation, Wistar rat

Functional organisation of behavioural inhibitory control mechanisms in cortico-basal ganglia circuitry: implications for stimulant use disorder.

The neural and psychological mechanisms of inhibitory control processes were investigated, focusing on the cortico-basal ganglia circuits in rats and humans. These included behavioural flexibility, ‘waiting’ and ‘stopping’ impulsivity and involved serial spatial reversal learning task in rodents, and in humans, premature responses in the Monetary Incentive Delay (MID) task and the stop-signal reaction time task. Chapter 2 and Chapter 3 focus on individual differences in behavioural flexibility in rats while Chapter 4, Chapter 5 and Chapter 6 consider how inhibitory control mechanisms are affected by the psychostimulant drug cocaine in both rats and humans. As reported in Chapter 2, systemic modulation of monoaminergic transmission by monoamine oxidase A (MAO-A) inhibitors enhanced reversal learning performance, selectively by decreasing the lose-shift probability, thereby implicating a role for dopamine, serotonin and noradrenaline in facilitating learning from negative feedback. Resting state functional magnetic resonance imaging (fMRI) revealed enhanced functional connectivity of the orbitofrontal and motor cortices as a correlate of flexible reversal learning performance, consistent with elevated levels of monoamines in these region (Chapter 3). Having clarified the mechanisms underlying behavioural flexibility in rats, Chapter 4 reports that escalation of intravenous cocaine self-administration induces behavioural inflexibility in rats even after a relatively short period of cocaine intake. Computational models, including a reinforced and Bayesian learner, revealed a lack of exploitation of the learned response-outcome relationships in cocaine-exposed rats. Chapter 5 focused on impulse control in human volunteers, identifying the striatal and cingulo-opercular networks as substrates of impulsive, premature responding in healthy 4 volunteers, stimulant-dependent individuals and their unaffected siblings. Loss of impulse control was elicited by different incentives for drug-free participants as opposed to drug users. Drug cues elicited striatal activation and increased premature responses in the stimulant-dependent group compared with the control group. In contrast, the ventral striatum was linked to incentive specific activation to reward anticipation. Task-based fMRI demonstrated that interactions between dorsal striatum and cingulo-opercular “cold cognition” networks underlie failures of impulse control in the control, at-risk and stimulant-dependent groups. However, whereas the cingulo-opercular networks were associated with premature responding in all groups, the reward system was activated specifically by the drug incentive cues in the stimulant group, and by monetary incentive cues in the drug-free groups. Chapter 6 presents evidence that corticostriatal functional and effective connectivity in an overlapping network that includes the anterior cingulate and inferior frontal cortices as well as motor cortex, the subthalamic nucleus and dorsal striatum, is critical to stopping impulse control in both control and cocaine individuals. No stopping efficiency impairments were observed in the cocaine-dependent group. Nevertheless, lower structural corticostriatal connectivity measured using diffusion MRI was associated with response execution impairments in cocaine participants performing a stop-signal reaction time task. Further, response execution was rescued by the selective noradrenaline reuptake inhibitor atomoxetine, which also increased corticostriatal effective connectivity. Finally, increased impulsivity and behavioural inflexibility seen in stimulant use disorder in Chapter 5 and Chapter 4, respectively, were not observed in the endophenotype at risk for developing stimulant abuse but were rather a consequence of stimulant abuse. These results further clarify the monoaminergic substrates of behavioural flexibility and specify the neural and computational impairments in inhibitory control induced by stimulant dependence.Pinsent Darwin Studentship from the Dept of Physiology, Development and Neuroscienc

La primera entrada en el laberinto en cruz elevado como predictor del nivel de ansiedad

RESUMEN Introducción: Generalmente el análisis del comportamiento exploratorio de ratas en laberinto en cruz elevado es realizado a la población general sin llevarse a cabo ningún tipo de discriminación entre individuos en función de sus decisiones exploratorias. Considerando la toma de decisiones para entrar a una zona del laberinto como un conflicto entre motivación de explorar y aversión,  el presente trabajo pretende evaluar la primera entrada a los brazos del laberinto como indicador del estado inicial de los niveles de motivación y aversión del entorno y en consecuencia, como indicador temprano de la evolución del comportamiento exploratorio.Materiales y métodos: Se evaluó el desempeño de ratas Wistar machos en laberinto en cruz elevado sometidas a una primera exposición, separándolas en dos grupos, de acuerdo a si su primera entrada fue en los brazos abiertos o en los brazos cerrados.Resultados: Aquellas ratas que primero entraron en los brazos abiertos obtuvieron valores significativamente mayores para el número de entradas y tiempo de permanencia en estos brazos en comparación con aquellas que entraron primero a los brazos cerrados; mientras que no se evidenció diferencias en el número de entradas en los brazos cerrados.Conclusión: La primera decisión del animal resulta predictiva del comportamiento durante los 5 minutos de exploración y permite discriminar las ratas entre dos niveles de ansiedad, sugiriéndose como variable discriminatoria el porcentaje de entradas a los brazos abiertos con punto de corte en 30,77%. Salud UIS 2010; 42:   Palabras clave: Aversión, comportamiento exploratorio, motivación, toma de decisión, ratas Wistar   ABSTRACT Introduction: Usually, the analysis of the rat exploratory behavior in elevated plus maze is carried out to the general population, without any discrimination between individuals as a function of their exploratory decisions. Considering the decision making to enter into a maze zone as a conflict between motivation to explore and aversion, the current work pretends to assess the first entry into the maze arms as indicator of the initial state of the motivation and aversion levels of the environment and therefore, as early indicator of the evolution of the exploratory behavior.Materials and methods: It was evaluated  the performance of male Wistar rats in elevated plus maze subjected to a first exposure, divided into two groups, according to whether its first entry was made into the open or closed arms.Results: Those rats that entered first into the open arms obtained higher significant values in the number of entries and time spent in these arms with respect to those rats that entered first into the closed arms; but it was not obtained differences in the number of entries into the closed arms.Conclusion: The first animal choice predicts the behavior during the 5 minutes of exploration and allows to discriminate the rats between two anxiety levels, being suggested the percentage of entries in open arms as discriminatory variable with cut-off value in 30.77%. Salud UIS 2010; 42:   Keywords: Aversion, decision making, exploratory behavior, motivation, Wistar rat