title: GnRH neurons elaborate a long-range projection with shared axonal and dendritic functions.
abstract: Information processing by neurons has been traditionally envisioned to occur in discrete neuronal compartments. Specifically, dendrites receive and integrate synaptic inputs while axons initiate and conduct spikes to distal neuronal targets. We report here in mice, using morphological reconstructions and electrophysiology, that the gonadotropin-releasing hormone (GnRH) neurons that control mammalian fertility do not conform to this stereotype and instead possess a single projection structure that functions simultaneously as an axon and dendrite. Specifically, we show that the GnRH neuron projection to the median eminence to control pituitary hormone secretion possesses a spike initiation site and conducts action potentials while also exhibiting spines and synaptic appositions along its entire length. Classical axonal or dendritic markers are not detectable in the projection process. Activation of ionotropic glutamate and/or GABA receptors along the GnRH neuron projection is capable of depolarizing the membrane potential and initiating action potentials. In addition, focal glutamate application to the projection is able to regulate the width of propagating spikes. These data demonstrate that GnRH neurons elaborate a previously uncharacterized neuronal projection that functions simultaneously as an axon and dendrite. This structure, termed a "dendron," greatly expands the dynamic control of GnRH secretion into the pituitary portal system to regulate fertility.
authors.affiliation: Centre for Neuroendocrinology, Department of Physiology, University of Otago School of Medical Sciences, Dunedin 9054, New Zealand.
authors.forename: Michel K
authors.initials: MK
authors.lastname: Herde
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Iremonger
authors.forename: Stephanie
authors.initials: S
authors.lastname: Constantin
authors.forename: Allan E
authors.initials: AE
authors.lastname: Herbison
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D001710:Biotin / Q000378:metabolism; D001808:Blood Vessels / Q000378:metabolism; D000075402:Channelrhodopsins; D003712:Dendrites / Q000502:physiology*; D018682:GABA Agents / Q000494:pharmacology; D037483:Galectin 1 / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D008297:Male; D008473:Median Eminence / Q000166:cytology; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010775:Photic Stimulation; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000235:genetics / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism
chemical_list: D000075402:Channelrhodopsins; D018682:GABA Agents; D037483:Galectin 1; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C492244:Viaat protein, mouse; D016875:tau Proteins; C077510:tau protein (182-235); D049452:Green Fluorescent Proteins; D007987:Gonadotropin-Releasing Hormone; D018698:Glutamic Acid; D001710:Biotin
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