Neonatal quinpirole treatment has been shown to produce an increase in dopamine D2-like receptor sensitivity that persists throughout the subject's lifetime. The objective was to analyze the effects of neonatal quinpirole treatment on effects of amphetamine in adolescent rats using locomotor sensitization and conditioned place preference procedures. Sprague-Dawley rats were treated with quinpirole (1 mg/kg) or saline from postnatal days (P)1 to P11 and raised to adolescence. For locomotor sensitization, subjects were given amphetamine (1 mg/kg) or saline every second day from P35 to P47 and were placed into a locomotor arena. In female rats, neonatal quinpirole treatment enhanced amphetamine locomotor sensitization compared with quinpirole-free controls sensitized to amphetamine. Male rats demonstrated sensitization to amphetamine, although this was muted compared with female rats, and were unaffected by neonatal quinpirole. For conditioned place preference, subjects were conditioned for 8 consecutive days (P32-39) with amphetamine (1 mg/kg) or saline and a drug-free preference test was conducted at P40. Rats treated with neonatal quinpirole enhanced time spent in the amphetamine-paired context compared with quinpirole-free controls conditioned with amphetamine, but only female controls conditioned with amphetamine spent more time in the drug-paired context compared with saline-treated controls. Increased D₂-like receptor sensitivity appears to have enhanced the behavioral effects of amphetamine, but these effects were more prevalent in adolescent female rats compared with male rats.

Previous studies have demonstrated that rats exposed to methamphetamine (MA) during the neonatal period display deficits in spatial learning and memory. The underlying correlates are; therefore, this study was devised to determine whether neuronal changes occur in the dentate gyrus (DG), nucleus accumbens (NAcc) and cortex of adult rats exposed to 10 mg/kg MA administered four times daily from P11-20 using Golgi-Cox staining [Gibb, R. & Kolb, B. (1998) J. Neurosci. Meth., 79, 1-4]. The DG and NAcc demonstrated a decrease in the number of spines per neuron and the NAcc showed an associated decrease in dendritic length. Selective changes in cortex were observed because increased dendritic length in the parietal cortex occurred with no change in the number of spines, and no differences were noted for either dendritic length or spines in the medial frontal cortex. The data suggest a potential cause for the learning and memory deficits induced by neonatal MA exposure; however, the underlying mechanism that produces these neuronal changes is.

No description available.

<p>Dendritic spines are mushroom-shaped appendages on the dendritic branches of neurons. They are invaluable to the function of the brain as they form the major site for excitatory signal transmission in the mammalian brain. These ubiquitous structures have several invaluable and unique characteristics – namely that their morphological and functional characteristics are activity-dependent and undergo remodeling as the spine experiences stimulation. This activity-dependent regulation then in turn modulates the excitatory postsynaptic potential that propagates into the adjacent parent dendrite, and which ultimately reaches the somatic compartment. The mediation of this modulatory effect on the postsynaptic signal by dendritic spines renders them invaluable to the brain’s ability to change neuronal circuits as it learns. The relationship between the structural and functional change in dendritic spines as plasticity is induced remains poorly understood; while efforts have been made to examine the morphology of dendritic spines during plasticity as well as the change to receptor insertion on the postsynaptic density, a comprehensive methodology to interrogate the concomitant changes to several aspects of dendritic spine structure and function as plasticity occurs has not been established. In this study, such a methodology was developed in order to facilitate future study of how a dendritic spine’s diffusional neck resistance, head volume, calcium-sensitive channels (on the postsynaptic density), and excitatory postsynaptic potential amplitude change concurrently as the spine undergoes activity-dependent regulation. This activity-dependent regulation also occurs in groups of spines called “clusters” <em>in vivo</em>, and the structural and functional dynamics of spines as these groups are formed also remains unknown. In order to to facilitate future <em>in vivo</em> studies on how clustered dendritic spines may change dynamically in both structure and function, a methodology for surgically accessing and recording calcium-based activity from the primary auditory cortex was developed, as the frequency-specific tuning of dendritic spines in this cortical area forms a compelling environment in which to study the relationship between spine form and function. </p>

This review provides a short historical background to the field of axonal regeneration and discusses the advances made in over 100 studies between 2007 and 2012 in understanding the molecular mechanisms underlying the conditioning lesion and regeneration of primary sensory axons in the dorsal columns of the spinal cord. Treatment strategies to stimulate axon growth and reinnervation of the spinal cord through the dorsal root entry zone and of the dorsal column nuclei in the medulla are highlighted. Major breakthroughs have been made, e.g., reinnervating the nucleus gracilis in the medulla using neurotrophic factor gradients and grafts as relays and identifying chondroitin sulfate proteoglycan receptors. The experimental accessibility of the dorsal column axons has also resulted in new technological advances, including live imaging. Last, future directions are discussed, including some challenges of translation to humans.

The purpose of this study was to identify central neuronal sites activated by stimulation of cardiac ischemia-sensitive afferent neurons and determine whether electrical stimulation of left vagal afferent fibers modified the pattern of neuronal activation. Fos-like immunoreactivity (Fos-LI) was used as an index of neuronal activation in selected levels of cervical and thoracic spinal cord and brain stem. Adult Sprague-Dawley rats were anesthetized with urethane and underwent intrapericardial infusion of an "inflammatory exudate solution" (IES) containing algogenic substances that are released during ischemia (10 mM adenosine, bradykinin, prostaglandin E2, and 5-hydroxytryptamine) or occlusion of the left anterior descending coronary artery (CoAO) to activate cardiac ischemia-sensitive (nociceptive) afferent fibers. IES and CoAO increased Fos-LI above resting levels in dorsal horns in laminae I-V at C2 and T4 and in the caudal nucleus tractus solitarius. Dorsal rhizotomy virtually eliminated Fos-LI in the spinal cord as well as the brain stem. Neuromodulation of the ischemic signal by electrical stimulation of the central end of the left thoracic vagus excited neurons at the cervical and brain stem level but inhibited neurons at the thoracic spinal cord during IES or CoAO. These results suggest that stimulation of the left thoracic vagus excites descending inhibitory pathways. Inhibition at the thoracic spinal level that suppresses the ischemic (nociceptive) input signal may occur by a short-loop descending pathway via signals from cervical propriospinal circuits and/or a longer-loop descending pathway via signals from the nucleus tractus solitarius.

Les connections synaptiques entre les cellules nerveuses (appelées synapses) sont essentielles à l’établissement de l’architecture du système nerveux. La modification de ces synapses est un des mécanismes par lequel l’apprentissage et la mémoire fonctionnent. On sait depuis plusieurs années déjà que la consommation de cannabis exerce une profonde influence sur l’apprentissage et la mémoire, et que sa consommation chez la femme durant la grossesse ou l’allaitement peut causer des déficits cognitifs chez l’enfant qui perdureront à l’âge adulte. Pour le moment, on ne sait toujours pas si ces effets sont médiés par les récepteurs aux cannabinoïdes classiques (CB1 et CB2) ou par d’autres récepteurs tel le GPR55. Des études récentes du laboratoire du Pr. Bouchard ont démontré un rôle important du système endocannabinoïde dans le développement du système nerveux notamment par la présence du récepteur GPR55 et son implication dans la modulation du guidage et de la croissance des axones durant les périodes foetale et périnatale. Comme certaines molécules et mécanismes cellulaires impliqués dans ces processus peuvent aussi jouer un rôle dans la formation de synapses (synaptogenèse), l’objectif de la présente étude est de déterminer la contribution du GPR55 dans la formation de contacts synaptiques. À partir de cortex d’embryons de souris, nous avons cultivé puis traité des neurones corticaux soit avec un agoniste sélectif de GPR55 (O-1602) ou son antagoniste sélectif (ML-193), soit avec un phytocannabinoïde (cannabidiol) pendant 24 heures au 9e jour in vitro. En immunocytochimie, les neurones traités avec le ML-193 ont démontré une réduction significative du nombre de contacts synaptiques et une augmentation significative avec l’O-1602 et le cannabidiol. Ces changements anatomiques sont corrélés avec des modifications de l’expression des protéines synaptiques GluR1 et synaptophysine au niveau du cortex. En plus de fournir d’importantes informations sur le développement du système nerveux, les résultats de cette étude contribuent à l’amélioration de nos connaissances sur les anomalies du développement induites par la consommation périnatale de cannabis. / Functional connections between nerve cells (called synapses) are essential to establish the architecture of the nervous system. The modification of synapses is thought to be one of the mechanisms by which learning and memory occur. It has been known for decades that cannabis consumption has a profound influence on learning and memory, and that maternal marijuana smoking during perinatal period causes cognitive deficits that last in the adulthood of the offspring. For the moment, we do not know if these effects are mediated by the classic CB1 and CB2 cannabinoid receptors or by other receptors such as GPR55. Recent studies by Pr. Bouchard have demonstrated an important role for the endocannabinoid system in the development of the nervous system, including the presence of GPR55 and its involvement in axon growth and target innervation during the fetal and early postnatal periods. As certain molecules and cellular mechanisms involved in these processes may also regulate synapse formation (synaptogenesis), the objective of the present study is to determine the contribution of GPR55 in the formation of new synaptic contacts. Primary cortical neurons isolated from embryonic mice were cultivated and then treated either with a selective agonist of GPR55 (O-1602) or his selective antagonist (ML-193), or with a phytocannabinoid (cannabidiol) for 24h at the ninth day in vitro (DIV9). In immunocytochemistry, neurons treated with ML-193 have shown a decrease in synaptic density, while the treatment with O-1602 or cannabidiol increased it. These anatomical changes were correlated with changes in the expression of synaptic proteins GluR1 and synaptophysin. Results from this study provide important insight on the development of the nervous system and contribute to improving our knowledge on developmental abnormalities induced by perinatal cannabis use.

The role that norepinephrine plays in regulating the concentration of different proteins in the parietal cortex, hippocampus and cerebellum was assessed by investigating the effects of either a bilateral lesion of the locus coeruleus or neonatal administration of 6-hydroxydopamine. Two weeks after lesioning the locus coeruleus, the concentration of two different proteins was elevated in the hippocampus; a third protein was reduced in concentration in this brain area as a result of the lesion. Three proteins were affected in concentration in the cerebellum after the locus coeruleus lesion - two were elevated in concentration and one was reduced in concentration. No proteins were altered in concentration in the parietal cortex as a result of the lesion. Seventy days after neonatal treatment with 6-hydroxydopamine, a total of 6 proteins were found to be changed. Four of these (one in the hippocampus and 3 in the parietal cortex) were reduced in concentration while two proteins (both in the cerebellum) were elevated in concentration after neonatal treatment with the catecholamine neurotoxin. There was little overlap between those proteins affected in concentration by the bilateral lesion of the locus coeruleus and those changed by neonatal treatment with 6-hydroxydopamine. These results suggest that the concentration of a number of different proteins may, under normal physiological conditions, be regulated in vivo by norepinephrine in the brain.

Fused in sarcoma (FUS) is an RNA binding protein involved in DNA repair and RNA metabolism, including mRNA transcription, splicing, transport and translation. FUS is genetically and pathologically associated with rare and aggressive forms of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). To explore the mechanisms by which pathogenic mutations in FUS cause neurodegeneration in ALS-FUS, we generated a series of FUS knock-in mouse lines that express the equivalent of the ALS-associated mutant proteins FUSP525L and FUSΔEX14 at physiological levels from the FUS locus. We demonstrate that heterozygous mutant FUS mice show progressive, age-dependent loss of vulnerable subpopulations of spinal motor neurons. While ALS-associated mutations in FUS lead to partial loss of function, we provide genetic evidence that the motor neuron phenotype observed is a consequence of a dose-dependent gain of function, associated with the insolubility of FUS and related RNA binding proteins (RBPs). Furthermore, we show that motor neuron degeneration is driven by cell autonomous mechanisms, associated with mutant FUS-independent inflammatory changes. In this faithful mouse model of ALS-FUS, we demonstrate that an antisense oligonucleotide (ASO) targeting the FUS transcript (ION363) results in the efficient silencing of both wild type and mutant FUS alleles, and that postnatal reduction of FUS protein levels in the brain and spinal cord delays disease onset in this mouse model of ALS-FUS. In a first-in-human trial of ION363, we demonstrate that repeated, intrathecal injections of this candidate therapeutic in an ALS patient with a FUSP525L mutation leads to the efficient silencing of both wild type and mutant FUS in the central nervous system, and a reduction in the burden of FUS aggregates that are a pathological hallmark of ALS-FUS. In mouse genetic and human clinical studies, we provide evidence in support of a therapeutic strategy by which silencing of the FUS gene may be used to prevent or delay disease onset in pre-symptomatic carriers of pathogenic FUS mutations, or to slow disease progression in symptomatic ALS- and FTD-FUS patients. In addition, we use this newly generated model to investigate the role of potential modifiers of FUS toxicity, including hnRNP U and UPF1, and study the role of chronic neuroinflammation in the disease progression that could lead to the development of novel therapeutics to provide immediate clinical benefit to patients with ALS-FUS.

Chemotherapy Induced Peripheral Neuropathy (CIPN) is known to impact negatively on patients' quality of life. It has been reported that these patients tend to have sensitivity thresholds to stimuli, such as pain and temperature, that are different from those of normal subjects. The effect of chemotherapeutic agents on the central nervous system (CNS) has been observed; however, most of the mechanisms involved are not exactly understood. A quantitative investigation into the temperature sensitivity changes in the spinal cords and brains of chemotherapy patients would provide important information in understanding the side effects of this treatment modality. In the first part of the project, the temperature perceptional changes in terms of brain activation patterns of the chemotherapy patients with CIPN are studied using brain function MRI. In the second part of the project, the structural changes of the brain and spinal cord of chemotherapy patients with CIPN are studied using diffusion tensor imaging (DTI). High b-value (b = 1500 s/mm2) and low b-value (b=650 s/mm2) settings will be use during the spinal cord DTI scans. Due to the sample size limitation, no comparison between healthy volunteers and CIPN patients can be done based on the existing temperature fMRI data. However, the developed temperature fMRI protocol shows good reliability in detecting temperature response. Based on the spinal cord DTI result using b = 1500 s/mm2, decrease in FA value has been observed. The corresponding FA values of CIPN patient and healthy volunteers are 0.28±0.10 and 0.41±0.02 , respectively. (t-test = 2.63 >2.447, p=0.05 level of significant) However, no significant difference is observed in other diffusion parameters. This results also suggests that application of high b-value setting is more suitable as it is better at detecting diffusion at microstructure. / Thesis / Doctor of Philosophy (PhD)