Oral Presentation The International Congress of Neuroendocrinology 2014

GnRH neurons- novel aspects of their anatomy and physiology. (#62)

Karl J Iremonger 1 , Michel K Herde 1 , Allan E Herbison 1
  1. Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand

Understanding how the gonadotropin-releasing hormone (GnRH) neurons generate unique profiles of hormone secretion across the estrus cycle has been a major challenge to researchers in the area of fertility. Research over the last 10 years has revealed that the morphology of GnRH neurons is very different compared to other central neurons. Specifically, they have very long, thin and unbranched dendrites. We have set out to understand how these unique dendrites integrate synaptic inputs, regulate spike generation and ultimately control GnRH peptide secretion. In order to study the function of GnRH neurons, we have used electrophysiology and functional imaging in acute brain slices in combination with dye filling and reconstructions of GnRH neuron morphology. These studies have revealed that the previously termed dendrite is the site of action potential initiation and projects uninterrupted to the median eminence. This projection possesses both axonal and dendritic properties. It is axon like in that it can initiate and actively propagate sodium action potentials. However, it also has dendritic properties in that it can receive and integrate synaptic inputs along its entire path to the median eminence. Because this projection is unlike any other described in the mammalian brain, we have named it the dendron. Ongoing work is using genetically encoded calcium indicators to understand how synaptic inputs onto the distal region of this projection can directly control the excitability of GnRH nerve terminals within the median eminence. Overall, these data suggest that the dendron greatly expands the dynamic control of GnRH secretion into the pituitary portal system to regulate fertility.