Regulation of LH in the female common brushtail possum (Trichosurus vulpecula)
type: CreativeWork
description: The seasonal control of reproduction, specifically the hypothalamic-pituitary-ovarian axis, has not been fully investigated in the common brushtail possum (Trichosurus vulpecula). This research aimed to characterise the control of pulsatile LH release and the seasonal change of LH in response to oestradiol in the possum through the development of two main hypotheses. The first hypothesis proposed that LH is secreted in pulses from the anterior pituitary gland in response to discrete pulses of GnRH released from the hypothalamus, both of which are modulated by the negative feedback effect of oestradiol. The second hypothesis proposed that the annual rhythm of reproduction in the possum is controlled via the hypothalamic-pituitary axis by an interaction between photoperiod and oestradiol. To achieve the study aims, preliminary work aimed to identify an anaesthetic that would allow blood collection from possums without compromising the hormones being measured. Ovariectomised female possums were anaesthetised with halothane, a ketamine xylazine combination or left conscious, and were challenged with GnRH. Ketamine-xylazine was found to be the most appropriate anaesthetic as it had little effect on serum LH concentrations before and during the GnRH challenge. The first hypothesis addressed the regulation of pulsatile LH in the female possum. To test whether the regulation of LH release occurs at the level of the hypothalamus or the pituitary gland, ovariectomised possums were anaesthetised with halothane or left untreated. Blood samples drawn at 10 minute intervals for 4 h showed that LH was released in distinct pulses (ranging between 0.75/h and 0.92/h). Halothane suppressed LH pulse frequency and amplitude. It is suggested that LH secretion is controlled at the level of the brain, as the pituitary gland was still responsive to exogenous GnRH during anaesthesia. To establish the site(s) of action of oestradiol within the hypothalamic-pituitary axis, ovariectomised possu…
abstract: The seasonal control of reproduction, specifically the hypothalamic-pituitary-ovarian axis, has not been fully investigated in the common brushtail possum (Trichosurus vulpecula). This research aimed to characterise the control of pulsatile LH release and the seasonal change of LH in response to oestradiol in the possum through the development of two main hypotheses. The first hypothesis proposed that LH is secreted in pulses from the anterior pituitary gland in response to discrete pulses of GnRH released from the hypothalamus, both of which are modulated by the negative feedback effect of oestradiol. The second hypothesis proposed that the annual rhythm of reproduction in the possum is controlled via the hypothalamic-pituitary axis by an interaction between photoperiod and oestradiol. To achieve the study aims, preliminary work aimed to identify an anaesthetic that would allow blood collection from possums without compromising the hormones being measured. Ovariectomised female possums were anaesthetised with halothane, a ketamine xylazine combination or left conscious, and were challenged with GnRH. Ketamine-xylazine was found to be the most appropriate anaesthetic as it had little effect on serum LH concentrations before and during the GnRH challenge. The first hypothesis addressed the regulation of pulsatile LH in the female possum. To test whether the regulation of LH release occurs at the level of the hypothalamus or the pituitary gland, ovariectomised possums were anaesthetised with halothane or left untreated. Blood samples drawn at 10 minute intervals for 4 h showed that LH was released in distinct pulses (ranging between 0.75/h and 0.92/h). Halothane suppressed LH pulse frequency and amplitude. It is suggested that LH secretion is controlled at the level of the brain, as the pituitary gland was still responsive to exogenous GnRH during anaesthesia. To establish the site(s) of action of oestradiol within the hypothalamic-pituitary axis, ovariectomised possu…
author: Herbert, Paul Alan
language: en
keywords: brushtail possum, Luteinizing Hormone (LH), Trichosurus vulpecula, oestradiol, steroid independent mechanism, pest control, seasonal reproductive control, possum, reproduction, Marsden::300603 Pests, health and diseases, Marsden::300405 Animal production (pests and pathogens)
license: https://researcharchive.lincoln.ac.nz/pages/rights
date published: 2003
date modified: 2026-07-24T02:50:54Z
provider: Lincoln University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Lincoln University

PropertyValue
property ID: Handle
value: https://hdl.handle.net/10182/1531