The neural mechanisms that support learning and memory are still poorly understood. Much work has focused on changes in neurotransmitter receptor expression, while changes in voltage-gated ion channel expression have been largely unexplored, despite the fact that voltage-gated ion channels govern neuronal excitability. Here we used eyeblink conditioning (EBC) in rats, a model of learning and memory with a well-understood neural circuit, to examine regulation of voltage-gated ion channels as a consequence of learning. EBC is a form of classical conditioning that involves pairings of a behaviorally neutral conditioned stimulus (CS) and an eyeblink eliciting unconditioned stimulus (US) over many trials to produce an eyeblink conditioned response (CR) to the CS in anticipation of the US. The acquisition and generation of the eyeblink CR is governed by plasticity at various sites in the cerebellum, both in the cerebellar cortex and the interpositus nucleus (IPN). Purkinje cells (PCs) are the primary neuron in the cerebellar cortex and these cells represent the sole output of the cerebellar cortex. PCs tonically inhibit the neurons of the IPN; the IPN is the start of the eyeblink pathway. In order for a CR to be generated, the inhibition of the IPN by PCs must be lifted. Basket cells (BCs) are small inhibitory interneurons that form synapses near the PC soma. These neurons are strategically located to strongly regulate PC output through inhibitory input near the axon hillock. BC axon terminals have the highest expression of Kv1.2, an alpha subunit of the Kv1 (Shaker) family of voltage-gated potassium channels, in the cerebellum. In addition, significant Kv1.2 expression is found on PC dendrites. Blocking Kv1.2 leads to increased GABAergic input to PCs and facilitates EBC. In the current work, we addressed the question of whether EBC itself regulates surface expression of Kv1.2 in cerebellar cortex. Rats received three days of either EBC, explicitly unpaired stimulus presentations, or no stimuli, and cerebellar tissue was harvested and analyzed via biotinylation/western blot (WB) and multiphoton microscopy (MP) techniques. In the first experiment, the Unpaired group showed significantly reduced surface Kv1.2 expression at BC axon terminals as measured by MP, but no changes observed with the WB measure, which measures expression at both BC axon terminals and PC dendrites. The second experiment used the same procedures but examined cerebellar tissue following a shorter training procedure. We hypothesized that the Paired and Unpaired groups would show similar Kv1.2 surface expression earlier in training. The Unpaired group showed increased surface Kv1.2 compared to the other two groups in the WB measures, but no differences were observed in the MP measure. Paired group rats that did not exhibit CRs showed the same pattern as the Unpaired group. Overall, we observed training and location specific changes in surface Kv1.2 expression, suggesting that learning does appear to regulate voltage-gated ion channel expression in the mammalian brain. Increased surface Kv1.2 early in training before CR expression emerges may set the stage for other mechanisms to govern the expression of the learned response. Prolonged stimulus input that is unmodulated by expression of a learned response, such as in the Unpaired group in the first experiment, leads to long-term changes in surface Kv1.2 expression exclusively at BC axon terminals.

Chronic or repeated exposure to stressful stimuli can result in several maladaptive consequences, including increased anxiety-like behaviors and altered peptide expression in brain structures involved in emotion. Among these structures, the bed nucleus of the stria terminalis (BNST) has been implicated in emotional behaviors as well as regulation of hypothalamic-pituitary-adrenal (HPA) axis activity. In rodents, chronic variate stress (CVS) has been shown to increase BNST pituitary adenylate cyclase activating polypeptide (PACAP) and its cognate PAC1 receptor transcript, and BNST PACAP signaling may mediate the maladaptive changes associated with chronic stress. In order to determine whether chronic stress would potentiate the behavioral and/or endocrine response to subthreshold BNST PACAP infusion, rats were exposed to a 7 day CVS paradigm previously shown to upregulate BNST PAC1 receptor transcripts; control rats were not stressed. Twenty-four hours following the last stressor, stressed and control rats were bilaterally infused into the BNST with 0.5 µg PACAP. Startle response to intra-BNST PACAP infusion was assessed post-infusion in Experiment 1. In Experiments 2 and 3, blood was sampled via a tail nick 30 min following PACAP infusion to assess the corticosterone response to PACAP following CVS. We found an increase in startle amplitude and an increase in plasma corticosterone levels 30 minutes following BNST PACAP infusion only in rats that had been previously exposed to CVS. These results were likely mediated via PAC1 receptors, as equimolar infusion of the VPAC1/2 receptor ligand vasoactive intestinal polypeptide (VIP) had no effect on plasma corticosterone levels. These results suggest that repeated exposure to stressors sensitizes the neural circuits underlying the behavioral and endocrine responses to BNST PACAP infusion and BNST PACAP/PAC1 receptor signaling likely plays a critical role in mediating stress responses.

The tendency of users to relapse severely hinders adequate treatment of addiction. Physical and psychological stressors often contribute to difficulties in maintaining behavior change, and may play a significant role in relapse. We have previously shown that the activation of pituitary adenylate cyclase activating peptide (PACAP) systems in the bed nucleus of the stria terminalis (BNST) mediates many consequences of chronic stressor exposure. Hence, chronic stress substantially increased BNST PACAP levels, intra-BNST PACAP infusions produced the behavioral and endocrine consequences of stressor exposure, and BNST PACAP antagonism blocked many of the consequences of chronic stress. In the present set of studies, we investigated the role of BNST PACAP in stress-induced reinstatement of cocaine seeking. Rats self-administered cocaine (3mg/ml; 0.5mg/ig/infusion, i.v.) for 1hr daily over 10 days, which was followed by extinction training in which lever pressing no longer resulted in cocaine delivery. In the first experiment we showed that intra-BNST PACAP infusion (1 μg; 0.5 μl per side) reinstated previously extinguished cocaine seeking behavior. In the second experiment intra-BNST infusions of the PAC1/VPAC2 antagonist, PACAP 6-38 (1 μg; 0.5 μl per side) blocked stress-induced reinstatement. Hence, stressor exposure (5 sec 2mA footshock) caused significant reinstatement of cocaine seeking behavior, which was blocked by intra-BNST PACAP6-38 infusion. Overall, these data suggest that BNST PACAP systems mediate stress-induced reinstatement to drug seeking. Understanding the neuropharmacology of BNST PACAP in stress-induced reinstatement and the role of PACAP systems may lead to viable targets for relapse prevention.

Bladder pain syndrome (BPS)/interstitial cystitis (IC) is a chronic pain disorder characterized by at least six weeks of lower urinary tract symptoms and unpleasant sensations (pain, pressure and discomfort) thought to be related to the urinary bladder and not meeting exclusion criteria. While the etiology is not known, BPS/IC may involve a "vicious circle" of uroepithelial dysfunction, inflammation and peripheral and central sensitization. We propose that the urinary bladder inflammatory insult partly mediates voiding dysfunction and visceral neurogenic pain characteristic of BPS/IC. Several studies from our laboratory have already demonstrated the role(s) of cytokines and their downstream targets in the functional alterations in micturition reflex pathways following chemically (cyclophosphamide, CYP)-induced cystitis. More recently, the pleiotropic protein, TGF-β, has been implicated in the pathogenesis of CYP-induced cystitis. TGF-β is activated locally at the initial site of injury by protease-dependent or protease-independent mechanisms to initiate a proinflammatory milieu. Depending on its contextual cues, TGF-β may then aid in resolving the primary immune response and support tissue repair. Though TGF-β is necessary to maintain normal immunological function, its aberrant expression and activation may have detrimental effects on responding tissues and cell types. A sustained increase in peripheral TGF-β reactivity, such as what may be observed in chronic inflammatory bladder conditions, may influence bladder afferent excitability to amplify nociceptive transmission and CNS input. The subsequent sensitization of peripheral afferent nociceptors at the level of the DRG or urothelium may promote spinal cord "wind-up" and cascade into visceral hyperalgesia and allodynia. In the first aim of this dissertation we investigated the functional profile of TGF-β isoforms and receptor (TβR) variants in the normal and inflamed (CYP-induced cystitis) urinary bladder with qRT-PCR, ELISA, IHC and in vivo cystometry. Our studies determined (i) the involvement of TGF-β in lower urinary tract neuroplasticity following urinary bladder inflammation, (ii) a functional role for TGF-β signaling in the afferent limb of the micturition reflex and (iii) urinary bladder TβR-1 as a viable target to reduce voiding frequency with cystitis. In the second aim of this dissertation we investigated the sensory components of the urinary bladder that may underlie the pathophysiology of aberrant TGF-β activation with bladder-pelvic nerve electrophysiology and luciferin-luciferase assays for ATP measurement. Our studies determined that TGF-β1 increased bladder afferent nerve excitability by stimulating ATP release from the urothelium via vesicular exocytosis mechanisms with minimal contribution from pannexin-1 channels. Furthermore, blocking aberrant TGF-β signaling in CYP-induced cystitis with TβR-1 inhibition decreased afferent nerve excitability with an equivalent decrease in ATP release. Taken together, these results establish a causal link between an inflammatory mediator, TGF-β, and intrinsic signaling mechanisms of the urothelium that may contribute to the altered sensory processing of bladder filling to facilitate increased voiding frequency. The distinct interactions of multiple mediators underscore the challenges for single target therapies and support the development of combinatory therapeutics for bladder dysfunction. Ultimately, these studies have increased our understanding of functional disorders and visceral pain and have the potential to improve the health of those suffering from inflammation-associated bladder syndromes.

ABSTRACT In humans, advanced malignancies are often targeted with broad-spectrum cytotoxic drugs that engender several detrimental side effects, in addition to their primary usage for eradicating cancerous cells. One of the lesser-researched of these effects, histological distortion of the olfactory system impedes a patient's ability to smell, perceive flavor, and ultimately may interfere with their nutritional intake and recovery from chemotherapy. Recent studies have indicated that cytotoxic drugs can damage gustatory epithelia immediately following administration (Mukherjee & Delay, 2011, 2013). We sought to observe the histological effects that cyclophosphamide (CYP), one of the oldest and most popular alkylating antineoplastic agents, may have on the murine main olfactory epithelium (MOE) and vomeronasal organ (VNO). We utilized two immunohistochemical antibodies to label cells in the olfactory epithelia: anti-Ki67, a marker strictly associated with cell proliferation; and, anti-Keratin 5, a marker for the cytoskeleton of horizontal basal cells. Twenty-eight C57BL/6 mice were administered a single intraperitoneal injection of CYP (75 mg/kg), while 20 control mice were administered saline, all at approximately seven weeks of age. Mice were euthanized at days one, two, six, 14, 30, and 45 post injection; subsequently, they were perfused with 4% paraformaldehyde, decalcified, cryoprotected, cryosectioned, and incubated with anti-Ki67 and anti-Keratin 5 antibodies, sequentially. Quantification results by fluorescent imaging of labeled sections revealed a significant decrease in the number of proliferative cells in the MOE and VNO of CYP-injected mice within the first 10 days post injection, followed by a compensatory period of increased cell proliferation through day 45 post injection, compared to saline-injected mice. Co-localization of horizontal basal cells and proliferative cells in the MOE and VNO of CYP-injected mice was significantly amplified at approximately 14 and 45 days post injection, respectively, compared to saline-injected mice. Our results suggest that administration of CYP can rapidly depress the populations of proliferative cells in the murine MOE and VNO; consequently, horizontal basal cells may afford restoration of the proliferative cell populations in the murine MOE and VNO, 14 to 45 days post injection, respectively.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system characterized by inflammation and demyelination. In addition to these hallmark features, MS also presents with axonal pathology, which is likely responsible for the signs and symptoms of the disease. Although prominent in MS, axonal pathology is frequently considered a consequence of demyelination and not a primary event. This conclusion is consistent with demyelination inducing the loss of specific axonal domains, known as the nodes of Ranvier that are responsible for the propagation of action potentials along the axon. In contrast, we propose that axonal pathology associated with MS is a primary pathological event, independent of demyelination, and not a product of it. In support of our hypothesis, we have analyzed a different axonal domain known as the axon initial segment. Whereas a single axon has numerous nodes of Ranvier uniformly distributed along the axon, each axon contains only a single axon initial segment that is positioned immediately distal to the neuronal cell body. The axon initial segment is responsible for action potential generation and modulation, and hence is essential for normal neuronal function. Background studies conducted by our lab, employing a murine model of demyelination/remyelination, revealed no correlation between axon initial segment stability and myelin integrity. Here we investigate the fate of the axon initial segment in human multiple sclerosis. While not statistically significant, we provide data demonstrating an apparent 40% reduction in AIS numbers in MS. We further provide qualitative evidence that AIS integrity in MS is not dependent on myelination suggestive that axonal pathology may be a primary event in MS, independent of demyelination. Our current findings are intriguing, but unfortunately this study is underpowered, and more samples will be required to determine whether this apparent reduction is statistically significant.

Feeding behavior and its associated neural circuitry is complex and intricate in mammalian systems, however, a simple model organism, such as C. elegans provides a more basic approach to understand factors and molecules involved. The fruit-dwelling nematode provides a unique set of resources; it only consists of 959 cells, 302 of which are neurons. In addition, each neuron’s connectivity and position within the worm is known and consistent between animals. Conservation of neurotransmitters and biochemical processes add to this impressive list. These resources provide an excellent background to address feeding behavior and the neural structures governing it. Feeding behavior in worms mimics feeding behavior in more complex organisms. They decide when to eat based on recent feeding behavior, current nutritional status, availability of food, and familiarity with the food available. Following starvation and refeeding worms enter a behavioral state similar to post-prandial sleep. The worms will stop eating and stop moving, in a state referred to as satiety quiescence. The ability to enter this state and maintain it is dependent on a pair of neurons in the head of C. elegans called ASI. Using calcium imaging and an automated satiety quiescence assay, our lab has found that this neuron pair is important for entering satiety quiescence and senses food. Feeding behavior, such as satiety quiescence, is regulated by numerous factors internal and external to the worm. Another pair of head neurons, ASH are capable of suppressing ASI’s activity in the presence of noxious stimuli and the presence of nutrients (potentially acting via ASI) can suppress ASH’s activation to noxious stimuli under starvation conditions. The interaction between these two neuron pairs can be regulated by other signals from the rest of the worm. We identified an opioid signal that can modulate the response of ASI to noxious stimulus signaling from ASH under starvation conditions. Other signals were identified to influence satiety behavior and this circuit including serotonin, octopamine, glutamate, and adenosine. In addition to these signals, a group of transcription factors were identified that may play a role in conveying the status of fat storage within the worm to its nervous system. Nuclear hormone receptors were found to increase their expression during starvation then decrease their expression upon refeeding. Upon completion of this work, we have a reached a greater understanding of the internal and external conditions governing feeding and avoidance behaviors.

Traumatic brain injury (TBI) is a serious health concern, causing cognitive, motor, and sensory deficits, including olfactory dysfunction. This dissertation explores the effects of TBI on synaptic plasticity within the olfactory system, seeking to define mechanisms guiding postinjury sensory reinnervation. Physical forces induced by TBI can axotomize olfactory receptor neurons (ORNs), which innervate olfactory bulb (OB). These axons regenerate OB projections after injury, a process involving growth through a complex extracellular matrix (ECM). As such, we investigated a potential molecular mechanism capable of modifying local OB ECM to support postinjury synaptogenesis. Since matrix metalloproteinases (MMPs) and their ECM substrates are recognized for TBI therapeutic potential, we explored the role of MMP9 and its substrate osteopontin (OPN) in promoting ORN reinnervation of the OB after mild fluid percussion injury (FPI). First, we confirmed that FPI deafferented the mouse OB. In Chapter 2, we showed concurrent activation of neuroglia, elevated spectrin proteolysis and reduction in ORN-specific olfactory marker protein (OMP). As OMP normalized during regeneration, growth associated protein-43kD (GAP-43) peaked, marking OB entry of ORN growth cones. Ultrastructural analysis revealed ongoing ORN axon shrinkage and degeneration, glial phagocytosis of cellular debris, and a reorganization of synaptic structure. To explore ECM role in mediating postinjury OB reinnervation, we defined the time course of MMP9 activity and several downstream targets. Chapter 3 reports biphasic MMP9 activity increase during acute/subacute degeneration, accompanied by robust generation of 48kD OPN cell signaling peptide. OPN receptor CD44 also increased during the acute/subacute interval, suggesting potential interaction of the two proteins. Finally, we utilized MMP9 knockout (MMP9KO) mice to confirm MMP9 role in OB synaptogenesis. In Chapter 4, MMP9KO reversed FPI-induced lysis of 49kD OPN and altered postinjury expression of ORN axon degeneration marker OMP. Additional ultrastructural analysis verified delayed recovery of OB synaptic features within the injured MMP9KO. Overall, we demonstrated that mild FPI elicits ORN axotomy to induce OB reactive synaptogenesis, and that MMP9 supports reinnervation by processing OPN for activation of local glia, cells which reorganize the ECM for synapse regeneration.

Spontaneously active monolayer neuronal networks cultured on photoetched multimicroelectrode plates (MMEPs) offer great potential for use in studying neuronal networks. However, there are many problems associated with frequent, long-term use of MMEPs. The major problems include (1) polysiloxane insulation deterioration and breakdown, (2) and loss of gold at the gold electroplated indium-tin oxide (ITO) electrodes. The objective of this investigation was to correct these major problems. Quality control measures were employed to monitor MMEP fabrication variables. The phenotypes of polysiloxane degradation were identified and classified. Factors that were found to contribute most to insulation deterioration were (1) moisture contamination during MMEP insulation, (2) loss of the quartz barrier layer from excessive exposure to basic solutions, and (3) repetitive use in culture. As a result, the insulation equipment and methods were modified to control moisture-dependent insulation deterioration, and the KOH reprocessing solution was replaced with tetramethylguanidine to prevent damage to the quartz. The problems associated with gold electroplating were solved via the addition of a pulsed-DC application of gold in a new citrate buffered electroplating solution.

Dans la première partie j'ai analysé des jeux de données de RNA-seq de transcriptome de petits ARNs disponibles dans les bases de données publiques. J'y ai observé 2 points intrigants : - une grande partie des lectures (bien que courtes) ne peux pas être alignée sur le génome de référence sans discordance et cette fraction non-alignable est parfois majoritaire. - de nombreuses lectures ont des tailles autours de 15-18nt qui ne correspondent à aucun type de petits ARNs connues, cette fraction est également majoritaires dans certains cas. Ces expériences sont souvent conçues pour la détection des miRNAs et l'analyse bioinformatique de ces données passent toujours par un alignement sur le génome de référence ou sur des séquences connues pour donner des petits ARNs. J'ai donc simplement éliminé la contrainte d'alignement dans l'analyse de ces données et effectué un regroupement des lectures par similarité (à la manière des ESTs). Ce regroupement donne une vision différente des données dans laquelle la notion de position génomique n'est plus centrale et ouvre la possibilité d'y découvrir des phénomènes non-standard. La deuxième partie est tirée d'une collaboration avec le laboratoire U675 INSERM. J'ai fait l'analyse bioinformatique des gènes dérégulés par la répression par RNAi du gène REST dans une lignée de neuroblastome de souris (N18). Ce gène est un facteur de transcription qui réprime les gènes neuronaux dans les cellules non neuronales. Ce répertoire de gènes dérégulés est potentiellement constitué de gènes clefs dans la biologie des neurones. / In first part of this thesis I have analysed small RNA-seq transcriptome data. I have noticed : - a large fraction of reads can't be aligned perfectly on reference genome - lot of reads are very short (15-18 nt) and don't match on previously known functionnal small RNAs. These experiments are designed for miRNA discovery and bioinformatics analysis of these data use alignments on genome or on known small RNA precursors sequences. I have eliminated the alignment and I have clustered these sequences. This clustering let me to observe these data with a new view in wich the genomic location is not central and open the gate to discover unconventional events. The second part is the analysis of deregulate genes by the silencing of the gene REST/NRSF in mouse N18 cell line. This gene is a transcription factor and it works as a repressor of neuronal genes in non neuronal cells. This deregulate genes repertoire potentially contains key genes in neuron biology. We found in this repertoire a network of genes centered on SWI/SNF complex including SMARCA2. This gene was associated to schizophrenia (SZ) in association studies and structural variation studies. In this network we found another genes associated to SZ. We show that these genes exhibit positive evolution in primate compare to rodents.