Alexandre Vidal
(Université d'Evry Val d'Essonne, France)
A model of the Gonadotropin Releasing Hormone secretion by hypothalamic neuron clusters

The secretion of Gonadotropin Releasing Hormone (GnRH) by specific hypothalamic neurons plays a major role in the neuroendocrine control of the reproduction function in mammals. While the qualitative properties of the physiological secretion pattern is common to all females, the quantitative properties characterize the specificities of the ovulatory cycle in each species. The difficulty to obtain in vivo time series of GnRH release by the hypothalamus spurs us on to develop a controllable model to study this complex biological system.

I will describe the qualitative properties of the physiological GnRH secretion pattern and introduce the types of specifications that the biological knowledge can specify in various species. I will present a model of the GnRH neuron secreting activities based on reaction-diffusion coupling of fast-slow oscillators. Applying bifurcation theory and a fast-slow analysis to a reduced model, I will show the model ability to reproduce the qualitative and species-dependent quantitative properties of the GnRH secretion pattern. Finally, I will display and discuss the synchronization/desynchronization alternation of the cluster activities reproducing subtle observable features but biologically misunderstood.