The mitral cells of the accessory olfactory bulb (AOB) of anuran frogs project their axons directly to the medial amygdala (MeA) along the accessory olfactory tract. An en bloc preparation of the telencephalon of the American bullfrog Lithobates catesbeiana was utilized to study a form of low-frequency inducible long-term potentiation (LTP) expressed at the synapse formed between the terminals of the accessory olfactory tract and the neurons of the MeA. Delivery of repetitive 1Hz-stimulation or sets of 5Hz tetani to the accessory olfactory tract both induced potentiation that was stable for over an hour, as measured by extracellular field recordings. LTP induced by 5Hz tetanus was associated with a decrease in paired-pulse ratio, which would be consistent with an increased probability of release contributing to the increased synaptic strength. Blockade of neither NMDA nor kainate glutamate receptors, with AP5 and UBP310 respectively, prevented LTP induction by 5Hz tetanus; however expression of LTP was partially masked in the presence of UBP310. These results suggest that kainate receptors are involved in the expression of LTP at the AOB-MeA synapse, though the means by which LTP is induced remains unclear. / Graduate / 2016-09-28

Chez la souris, la puberté de la femelle est accélérée par des phéromones urinaires émises par le mâle (effet Vandenbergh). Les mécanismes neuroendocriniens sous-Jacents et les conséquences comportementales restent peu connus. Par une approche multidisciplinaire alliant immunohistochimie, chromatographie gazeuse couplée à la spectrométrie de masse et chirurgie expérimentale, mon travail de thèse montre que les neurones synthétisant la kisspeptine, un neuropeptide hypothalamique jouant un rôle essentiel dans le contrôle de la puberté, sont régulés positivement par les phéromones accélératrices de la puberté. Les neurones à kisspeptine reçoivent le signal phéromonal via le système olfactif accessoire et le transmettent aux neurones à GnRH. De plus, des analyses comportementales montrent qu’outre leur effet physiologique connu, les phéromones accélératrices de la puberté modifient à long terme le comportement sexuel de la souris femelle. En effet, la préférence de la femelle pour l’odeur du mâle s’exprime plus tôt à l’âge adulte après l’exposition péripubère aux phéromones émises par la souris mâle. / In the mouse, female puberty onset is accelerated by male urinary pheromones (Vandenbergh effect). The neuroendocrine mechanisms underlining this effect and the behavioral consequences are poorly understood. Through a multidisciplinary approach using immunohistochemistry, gas chromatography coupled to mass spectrometry and experimental surgery, my thesis research show that neurons that synthesize kisspeptin, a hypothalamic neuropeptide which plays a master role in the control of puberty onset, are positively regulated by puberty-Accelerating pheromones. Kisspeptin neurons receive pheromone signal via the accessory olfactory system and transmit it to GnRH neurons. Moreover, behavioral analyses show that besides their known physiological effect, puberty-Accelerating pheromones also have long-Term effects on sexual behavior of the female mouse. Indeed, puberty-Accelerating pheromones induce a precocious expression of male-Directed odor preference in adult female mice.