Le noyau paraventriculaire (PVN) de l'hypothalamus régule une série de phénomènes physiologiques incluant l'équilibre énergétique et la pression artérielle. Nous avons identifié une cascade de facteurs de transcription qui contrôle le développement du PVN. SIM1 et OTP agissent en parallèle pour contrôler la différenciation d'au moins cinq types de neurones identifiables par la production d'OT, AVP, CRH, SS et TRH. Ces Facteurs de transcriptions contrôlent le développement des lignées CRH, AVP et OT en maintenant l'expression de Brn2 qui à son tour est nécessaire pour la différenciation terminale de ces neurones. L'analyse du transcriptome du PVN nous a permis d'identifier plusieurs gènes qui ont le potentiel de contrôler le développement du PVN. Nous voulons développer un paradigme de perte de fonction qui permettrait l'étude de ces gènes candidats sur une grande échelle. Le but de ce projet est de caractériser le PVN en développement de l'amphibien en vue de l'utilisation de ce modèle pour des études fonctionnelles. Nous avons cloné des fragments de cDNA de Sim1, OTP, Brn2, Sim2, CRH, Ot, AVP et TRH à partir de l'ARN total de Xenopus Laevis. Nous avons adapté notre technique d'hybridation in situ pour caractériser l'expression de ces gènes chez l'amphibien aux stades 33-39, 44, 51, 54, 60, et chez l'adulte. Résultats. Les Facteurs de transcription Sim1, OTP, et Brn2 commencent à être exprimés dans le PVN prospectif au stade 33. L'expression des marqueurs de différenciation terminale devient détectable entre les stades 37 et 39. De façon intéressante, le PVN occupe initialement un domaine de forme globulaire puis à partir du stade 44 s'allonge le long de l’axe dorso-ventral. Cet allongement se traduit par une organisation en colonnes des cellules du PVN que nous n'avons pas observée chez les rongeurs. Le développement du PVN est conservé chez l'amphibien dans la mesure où la relation entre l'expression des facteurs de transcription et des marqueurs de différenciation terminale est conservée. Il existe par ailleurs des différences entre la topographie des PVN des mammifères et de l'amphibien. L'organisation en colonnes de cellules pourrait correspondre à des mouvements de migration tangentielle. Nous sommes maintenant en mesure de tester la fonction des facteurs de transcription dans le PVN par l'approche d'invalidation par morpholinos. / The paraventricular nucleus PVN of the hypothalamus regulates a series of physiological phenomena including the maintenance of energetic balance and arterial blood pressure. We have previously identified a cascade of transcription factors that control the development of the PVN. Sim1 and OTP act in concert to mediate the terminal differentiation of at least five types of neurons identifiable by their production of OT, AVP, CRH, SS and TRH. These transcription factors control the development of the OT, AVP and CRH producing neurons by maintaining the expression of Brn2, which is in turn required for the terminal differentiation of these cell lines. The transcriptome analysis of the PVN allowed us to identify a handful of genes that are potentially implicated in the development of this brain structure. Our goal is to develop a loss of function paradigm that would allow a high troughput study of these candidate genes. The main goal of this project is to characterize the developing PVN in the amphibian in order to use this model in our functional studies of these genes. We have cloned fragments of cDNA of Sim1, OTP, Brn2, Sim2, CRH, TRH, AVP and OT using Xenopus laevis total RNA. We have also adapted our in situ hybridization technique to characterize the expression of these genes in stage 33-39, 44, 51, 54, 60 and adult amphibian brain. Sim1, OTP and Brn2 are expressed in the prospective PVN as soon as stage 33. The expression of the terminal differentiation markers become detectable between stages 37-39. Interestingly, the PVN is initially restricted to a more globular domain and begins to extend along the dorso-ventral axis at around stage 44. This vertical extension translates into a column organization that we do not observe in rodents. The development of the PVN is well conserved in the amphibian in the sense that the relation between the expression of the different transcription factors and the terminal differentiation markers is conserved. We can also observe some topographical differences between the mammalian and amphibian PVN. The column organization the different PVN cell types might correspond to the tangential migration that is observed in the mouse. We are now well equipped to test the function in the PVN of the known transcripton factors as well as the candidate genes previously identified in our lab using a morpholino-mediated gene knock down.

Le noyau paraventriculaire (PVN) de l'hypothalamus régule une série de phénomènes physiologiques incluant l'équilibre énergétique et la pression artérielle. Nous avons identifié une cascade de facteurs de transcription qui contrôle le développement du PVN. SIM1 et OTP agissent en parallèle pour contrôler la différenciation d'au moins cinq types de neurones identifiables par la production d'OT, AVP, CRH, SS et TRH. Ces Facteurs de transcriptions contrôlent le développement des lignées CRH, AVP et OT en maintenant l'expression de Brn2 qui à son tour est nécessaire pour la différenciation terminale de ces neurones. L'analyse du transcriptome du PVN nous a permis d'identifier plusieurs gènes qui ont le potentiel de contrôler le développement du PVN. Nous voulons développer un paradigme de perte de fonction qui permettrait l'étude de ces gènes candidats sur une grande échelle. Le but de ce projet est de caractériser le PVN en développement de l'amphibien en vue de l'utilisation de ce modèle pour des études fonctionnelles. Nous avons cloné des fragments de cDNA de Sim1, OTP, Brn2, Sim2, CRH, Ot, AVP et TRH à partir de l'ARN total de Xenopus Laevis. Nous avons adapté notre technique d'hybridation in situ pour caractériser l'expression de ces gènes chez l'amphibien aux stades 33-39, 44, 51, 54, 60, et chez l'adulte. Résultats. Les Facteurs de transcription Sim1, OTP, et Brn2 commencent à être exprimés dans le PVN prospectif au stade 33. L'expression des marqueurs de différenciation terminale devient détectable entre les stades 37 et 39. De façon intéressante, le PVN occupe initialement un domaine de forme globulaire puis à partir du stade 44 s'allonge le long de l’axe dorso-ventral. Cet allongement se traduit par une organisation en colonnes des cellules du PVN que nous n'avons pas observée chez les rongeurs. Le développement du PVN est conservé chez l'amphibien dans la mesure où la relation entre l'expression des facteurs de transcription et des marqueurs de différenciation terminale est conservée. Il existe par ailleurs des différences entre la topographie des PVN des mammifères et de l'amphibien. L'organisation en colonnes de cellules pourrait correspondre à des mouvements de migration tangentielle. Nous sommes maintenant en mesure de tester la fonction des facteurs de transcription dans le PVN par l'approche d'invalidation par morpholinos. / The paraventricular nucleus PVN of the hypothalamus regulates a series of physiological phenomena including the maintenance of energetic balance and arterial blood pressure. We have previously identified a cascade of transcription factors that control the development of the PVN. Sim1 and OTP act in concert to mediate the terminal differentiation of at least five types of neurons identifiable by their production of OT, AVP, CRH, SS and TRH. These transcription factors control the development of the OT, AVP and CRH producing neurons by maintaining the expression of Brn2, which is in turn required for the terminal differentiation of these cell lines. The transcriptome analysis of the PVN allowed us to identify a handful of genes that are potentially implicated in the development of this brain structure. Our goal is to develop a loss of function paradigm that would allow a high troughput study of these candidate genes. The main goal of this project is to characterize the developing PVN in the amphibian in order to use this model in our functional studies of these genes. We have cloned fragments of cDNA of Sim1, OTP, Brn2, Sim2, CRH, TRH, AVP and OT using Xenopus laevis total RNA. We have also adapted our in situ hybridization technique to characterize the expression of these genes in stage 33-39, 44, 51, 54, 60 and adult amphibian brain. Sim1, OTP and Brn2 are expressed in the prospective PVN as soon as stage 33. The expression of the terminal differentiation markers become detectable between stages 37-39. Interestingly, the PVN is initially restricted to a more globular domain and begins to extend along the dorso-ventral axis at around stage 44. This vertical extension translates into a column organization that we do not observe in rodents. The development of the PVN is well conserved in the amphibian in the sense that the relation between the expression of the different transcription factors and the terminal differentiation markers is conserved. We can also observe some topographical differences between the mammalian and amphibian PVN. The column organization the different PVN cell types might correspond to the tangential migration that is observed in the mouse. We are now well equipped to test the function in the PVN of the known transcripton factors as well as the candidate genes previously identified in our lab using a morpholino-mediated gene knock down.

Anxiety is an affective state defined by heightened arousal and unease in the absence of a clear and present fear-inducing stimulus. Chronic and inappropriate anxiety leads to anxiety disorders, the most common class of human mental disorder. Recent work suggests projections to the ventral tegmental area (VTA), are critical for anxiety behavior expression. However, the relationship between efferent VTA projections and anxiety is unclear. This thesis resolves anxiety circuitry connecting the dopaminergic (DAergic) VTA to the interpeduncular nucleus (IPN), coined the mesointerpeduncular circuit. I hypothesize the mesointerpeduncular circuit affects anxiety through the release of anxiogenic corticotropin releasing factor (CRF) during nicotine withdrawal and anxiolytic dopamine (DA) during drug naïve behavior. Electrophysiological and pharmacological data suggest CRF release from the DAergic VTA during nicotine withdrawal activates CRF receptor 1 (CRFR1) potentiating the glutamatergic activation of “Type 2” neurons and anxiety-like behavior in mice. However, in nicotine naïve conditions CRF production is negligible. Instead, in vivo DA release is anticorrelated with anxiety-like behaviors. Optogenetic stimulation and inhibition drives decreased and increased anxiety-like behaviors, respectively. Electrophysiological experiments reveal a complex interpeduncular microcircuit where D1-like DA receptor expressing “Type C” neurons in the caudal IPN (cIPN) regulate glutamatergic release in the ventral IPN (vIPN) through presynaptic GABA receptors. The result is propagation of the signal to excite “Type A” and inhibit “Type B” vIPN neurons. Finally, pharmacological activation or inhibition of interpeduncular D1-like DA receptors is sufficient to decrease and increase anxiety-like behaviors respectively. Thus, this circuit is important for modulating anxiety-like behavior.

Dissertation "The influence of corticosterone and corticoliberin on damage of the hippocampus and their relation to cognition" deals with the cognitive, behavioral and histological changes in experimental rat strain long-evans that closer describe the consequences of long-term continuous application of corticoliberin and/or corticosterone. Testing of the behavioral changes was divided into two phases. The first one - within three or fourweeks respectively administration of these hormones, therefore until their early effects - and the second phase - after four weeks of completion of the first phase at the time of the possible late effects. In the twelfth week the experimental animals were killed and in the group which had exogenously elevated corticosterone, the morphological changes in the hippocampus were monitored and measured. In all experimental groups alteration of behavior was observed. Histological and morphological changes in the brain we have found. Layout of experiments in two testing phases allowed differentiation of the early changes and the late and persistent changes. The arrangement of experiments allowed the choice of tests to compare not only individual effects of both hormones (corticoliberin and corticosterone) but also their coactioning and biological responses to them. Using a wider...

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