Gonadotropin-releasing hormone (GnRH) neurons are regulated by numerous neurotransmitters, neurotrophic factors, and by steroid hormone feedback. While this apparent multiplicity of inputs may seem redundant, in fact it is crucial for the organism to be able to integrate information about the internal homeostatic milieu, as well as external stimuli, in order to ensure that reproduction and behavior are coordinated. Moreover, while inputs to GnRH neurons may overlap in their stimulatory or inhibitory actions, the GnRH neurons themselves have a unique role in reproductive physiblogy. In the absence of these cells, reproduction cannot occur. The natural mutation of Kallmann’s syndrome in humans, and the hypogonadal mouse, in which GnRH neurons do not develop properly, are the most compelli g examples of the primacy of GnRH neurons, as individuals with these mutations never attain reproductive competence unless GnRH (or its downstream targets) is replaced.
KeywordsVasoactive Intestinal Peptide Median Eminence Arcuate Nucleus GnRH Neuron GnRH Release
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