GnRH Neurons: Changes Across the Life Cycle
GnRH-1 neurons undergo developmental changes beginning in the embryonic period and continuing throughout the life of the organism. Some of the changes in hypophysiotropic GnRH neurons are intrinsic to these cells, and others are due to alterations in inputs that affect their function. The following discussion of changes in GnRH neurons across the life cycle of the organism will be broken down into four developmental phases. First, the embryonic origin and migration of GnRH neurons will be discussed. This phenomenon is particularly interesting and unusual, as GnRH neurons are born outside of the brain in the olfactory placode, and migrate into the central nervous system and hypothalamus during embryogenesis. Second, GnRH neurons will be considered during postnatal development and puberty. The activation of GnRH neurons during development is the critical event for the attainment of adult reproductive function, and thus developmental changes in the GnRH neurosecretory system during the pubertal period are crucial to this process. Third, GnRH neurons and their regulation of reproductive function in females and males during adulthood will be discussed. This section will include the negative and positive feedback regulation of GnRH neurons in females, with its relationship to ovulation, and negative feedback regulation of GnRH neurons by steroid hormones in males. Fourth, changes in GnRH neurons during reproductive senescence will be discussed.
KeywordsMigration Estrogen Morphine Serotonin Testosterone
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