Castration-Induced Modifications of GnRH-Elicited [Ca2þ]i Signaling Patterns in Male Mouse Pituitary Gonadotrophs In Situ: Studies in the Acute Pituitary Slice

Gonadotropin-releasing hormone (GnRH) binds to pituitary gonadotroph receptors and initiates [Ca2+]i signals and gonad-otropin secretion. Here, we recorded GnRH-induced Ca2+ signals in acute pituitary slices from both intact and castrated male mice 15 and 45 days after orchiectomy (GnX). Cells responding with ‘‘noncanonical’ ’ sequences of Ca2+ signaling to increasing GnRH concentrations ([GnRH]; oscillatory respons-es at a given [GnRH] and transient responses at both lower and higher concentrations) were augmented significantly in the castrated mice. Also, 15 days after GnX the number and size of gonadotrophs were augmented, confirming earlier anatomical studies. Hypertrophied gonadotrophs after 15 days after GnX tended to display GnRH-induced Ca2+ responses of greater amplitude. Furthermore, median effective dose (ED50) fo