The Gonadotropin-Releasing Hormone Pulse Generator

Area of Science:

• Neuroendocrinology
• Reproductive Biology
• Mammalian Physiology

Background:

• Pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) is vital for mammalian fertility.
• LH pulse frequency varies between sexes and reproductive phases (e.g., hourly in follicular phase, every 2-3 hours in luteal phase/males).
• Identifying the precise mechanism and location of the "GnRH pulse generator" has been a long-standing research objective.

Purpose of the Study:

• To review the historical and current understanding of the GnRH pulse generator.
• To evaluate evidence supporting different hypotheses regarding the GnRH pulse generator's location and cellular basis.
• To synthesize findings across species regarding the identification of the GnRH pulse generator.

Main Methods:

• Review of scientific literature spanning 50 years.
• Analysis of studies investigating GnRH and LH secretion patterns.
• Examination of evidence for intrinsic vs. extrinsic pulse generation mechanisms.
• Focus on arcuate nucleus and kisspeptin neuron involvement.

Main Results:

• Little evidence supports an intrinsic GnRH neuron-based pulse generation mechanism.
• Strong evidence points to an extrinsic pulse generator within the arcuate nucleus.
• A subpopulation of arcuate kisspeptin neurons is identified as the GnRH pulse generator in rodents.
• Findings in other species generally support arcuate/infundibular kisspeptin neurons as the mammalian GnRH pulse generator.

Conclusions:

• Kisspeptin neurons in the arcuate nucleus are the likely mammalian GnRH pulse generator.
• Past electrophysiological recordings may have inadvertently captured kisspeptin neuron activity.
• Mechanisms of synchronicity and afferent modulation of these neurons remain largely unknown.