ZFIN ID: ZDB-PUB-100614-7
Acquisition of Spontaneous Electrical Activity During Embryonic Development of Gonadotropin-Releasing Hormone-3 Neurons Located in the Terminal Nerve of Transgenic Zebrafish (Danio rerio)
Ramakrishnan, S., Lee, W., Navarre, S., Kozlowski, D.J., and Wayne, N.L.
Date: 2010
Source: General and comparative endocrinology   168(3): 401-407 (Journal)
Registered Authors: Kozlowski, David J., Navarre, Sammy
Keywords: action potential, electrophysiology, embryo, teleost
MeSH Terms:
  • Animals
  • Animals, Genetically Modified/embryology
  • Animals, Genetically Modified/metabolism
  • Electrophysiology
  • Embryonic Development/genetics
  • Embryonic Development/physiology*
  • Gonadotropin-Releasing Hormone/genetics
  • Gonadotropin-Releasing Hormone/metabolism*
  • Green Fluorescent Proteins/genetics
  • Green Fluorescent Proteins/metabolism
  • Immunohistochemistry
  • Neural Crest/embryology
  • Neurons/metabolism*
  • Pyrrolidonecarboxylic Acid/analogs & derivatives*
  • Pyrrolidonecarboxylic Acid/metabolism
  • Zebrafish/embryology*
  • Zebrafish/metabolism*
PubMed: 20515692 Full text @ Gen. Comp. Endocrinol.
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ABSTRACT
There are multiple populations of gonadotropin releasing hormone (GnRH) neurons that have distinct physiological and behavioral functions. Teleost fish have a population of GnRH3 neurons located in the terminal nerve (TN) associated with the olfactory bulb that is thought to play a neuromodulatory role in multiple physiological systems, including olfactory, visual, and reproductive. We used transgenic zebrafish in which the GnRH3 promoter drives expression of a green fluorescent protein to identify GnRH3 neurons during development in live embryos. Unlike with hypophysiotropic GnRH neurons of zebrafish, TN-GnRH3 neurons are of neural crest origin and are one of the first populations of GnRH neurons to develop in the early embryo. Using a combination of optical imaging and electrophysiology, we showed that during the first three days post-fertilization, TN-GnRH3 neurons increase in number, extend neural projections, move in association with tissue expansion, and acquire an adult-pattern of spontaneous action potential firing. Early during development, about half of the neurons were quiescent/non-firing. Later, at three days post-fertilization, there was an increase in the proportion of neurons showing action potential firing and an increase in the number of neurons that showed an adult-like tonic or beating pattern of action potential firing with a firing frequency similar to that seen in adult TN-GnRH3 neurons. This study represents the first neurophysiological investigation of developing GnRH neurons in live embryos -- an important advance in understanding their potential non-reproductive roles during embryogenesis.
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