Acute and Long-Term Changes in Central and Pituitary Mechanisms Regulating Pulsatile Luteinizing Hormone Secretion after Ovariectomy in the Rat

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Abstract
These experiments examined the time course of changes in the characteristics of pulsatile luteinizing hormone (LH) secretion that occur after ovariectomy (OVX) in the rat, and compared the response of the brain and pituitary to the absence of ovarian steroid negative feedback. The literature indicates that the brain could respond to OVX by altering the frequency and/or amplitude of the pulsatile luteinizing hormone releasing hormone (LH-RH) release which triggers pulsatile LH secretion, while the pituitary could respond by altering basal LH output and/or its response to LH-RH. In vivo experiments examined changes in mean blood LH levels, LH pulse amplitudes and pulse frequencies in control rats on diestrus 1 (Dl) and at 7 h, 14 h, 1, 2 or 8 days, or 3 weeks following OVX. In addition, anterior pituitaries from rats on Dl or rats ovariectomized for 1, 2 or 8 days, or 3 weeks, were incubated in vitro with or without LH-RH to examine changes in both basal and LH-RH-induced LH release.