title: Gonadotropin releasing hormone (GnRH) modulates odorant responses in the peripheral olfactory system of axolotls.
abstract: Peripheral signal modulation plays an important role in sensory processing. Activity in the vertebrate olfactory epithelium may be modulated by peptides released from the terminal nerve, such as gonadotropin releasing hormone (GnRH). Here, we demonstrate that GnRH modulates odorant responses in aquatic salamanders (axolotls, Ambystoma mexicanum). We recorded electrical field potentials (electro-olfactograms, or EOGs) in response to stimulation with four different amino acid odorants, L-lysine, L-methionine, L-cysteine, and L-glutamic acid. EOG responses were recorded from the main olfactory epithelium before, during, and after application of 10 microM GnRH. This protocol was repeated for a total of three trials with 60-80 min between trials. The effect of GnRH on EOG responses was broadly similar across odorants and across trials. In general, EOG responses were reduced to 79% of the initial magnitude during application of GnRH; in some trials in which glutamic acid served as the odorant, EOG responses were enhanced during the wash period. Although the 4-min inter-stimulus interval did not lead to adaptation of EOG responses during the first trial, we frequently observed evidence of adaptation during the second and third trials. In addition, we found that lower concentrations of GnRH produced a smaller effect. These results demonstrate that GnRH can modulate odorant responses in the peripheral olfactory system.
authors.affiliation: Department of Zoology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Daesik
authors.initials: D
authors.lastname: Park
authors.forename: Heather L
authors.initials: HL
authors.lastname: Eisthen
mesh_terms: D000558:Ambystoma mexicanum; D000818:Animals; D003545:Cysteine / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D018698:Glutamic Acid / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology / Q000502:physiology*; D008239:Lysine / Q000502:physiology; D008297:Male; D008715:Methionine / Q000502:physiology; D009812:Odorants; D009831:Olfactory Mucosa / Q000187:drug effects / Q000502:physiology*; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000502:physiology*
chemical_list: D007987:Gonadotropin-Releasing Hormone; D018698:Glutamic Acid; D008715:Methionine; D008239:Lysine; D003545:Cysteine