Initiation and propagation of action potentials in Gonadotropin-Releasing Hormone Neuron Dendrites

Abstract

Gonadotropin-releasing hormone (GnRH) neurons are the final output neurons in a complex neuronal network that regulates fertility.The morphology of GnRH neuron dendrites is very different to other central neurons in that they are very long, thin, and unbranched. Tostudy the function of these dendrites, we have used Na_ and Ca2_ imaging in combination with dual soma and dendrite electricalrecordings in brain slices from GnRH-GFP mice. Here, we show that GnRH neurons actively propagate Na_ spikes throughout theirdendrites. Multisite dendritic recordings confirmed that these spikes were observed in one of the dendrites before the soma in the greatmajority of neurons tested. Na_imaging experiments revealed that the initial 150_mof dendrite has a higher density of functional Na_channels than more distal regions, suggesting that this region of dendrite is highly excitable andmaybe the site of spike initiation. Finally,we show that the depolarization from dendritic spikes opens voltage-gated Ca2_ channels giving rise to dendritic Ca2_ transients.Together, these findings suggest that the proximal dendrites of GnRH neurons are highly excitable and are likely to be the site of actionpotential initiation in these neurons. © 2012 the authors.