In-vivo properties and functional subtypes of gonadotropin-releasing hormone neurons.

Although the gonadotropin-releasing hormone (GnRH) neurons play a pivotal role in mammalian fertility, their activity patterns and functional classification during ovulation and across reproductive cycles still remain elusive. By integrating in vivo electrophysiological recording with chemogenetic technology, we successfully identified GnRH neurons in freely moving mice. Recordings obtained revealed that the baseline firing rates of rostral preoptic area (rPOA) GnRH neurons were significantly higher during proestrus compared to the metestrous and estrous stages of the cycle. Continuous 20-h recordings showed surge-like activity in a subpopulation of GnRH neurons (∼47%) during the proestrous stage, characterized by diverse firing patterns, while other GnRH neurons exhibited basal rhythmic firing patterns. The similar waveform characteristics of GnRH neurons facilitate their identification for subsequent in vivo electrophysiology studies. This study represents a significant milestone in functionally classifying GnRH neurons in vivo and holds great importance for investigating neuroendocrine regulation of female reproduction.