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Title: Neural mechanisms involed in the regulation of oxytocin secretion in late pregnant rats
Author: Antonijevic, Irna A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1995
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In the present work, I have investigated the role of oxytocin, a peptide hormone synthesised in the paraventricular and supraoptic (SON) nuclei of the hypothalamus and secreted from axon terminals in the posterior pituitary, in the initiation and maintenance of parturition in rats. Furthermore, I have studied afferent pathways involved in the secretion of oxytocin at the end of pregnancy, using immunocytochemical detection of Fos, the protein product of the immediate early gene c-fos. First, I have shown that delivery in rats, that has been disrupted by a systemic injection of morphine, which prevents pituitary oxytocin release, can be restored by pulsatile but not continuous administration of physiological doses of oxytocin, indicating a critical role of pulsatile oxytocin for the normal progress of delivery. Following from there, I have shown that labour and delivery can be induced in late pregnant rats with pulsatile administration of oxytocin, while systemic administration of peptide oxytocin antagonists can delay the onset of delivery and prolong its progress. Using Fos immunocytochemistry, I have demonstrated that Fos expression is increased in the SON and in putative afferent neurones, including those in the nucleus tractus solitarii (NTS) in the brainstem, in parturient compared to prepartum rats. Similarly, Fos expression in these areas can be induced by a systemic injection of cholecystokinin, that is known to excite magnocellular oxytocin neurones and hormone release, indicating the involvement of NTS neurones in the regulation of oxytocin secretion. Following from there, I have shown when oxytocin-induced labour, Fos expression in the NTS and the SON is increased even before delivery of pups, suggesting that vagino-cervical stimulation is not a prerequisite for activation of supraoptic neurones at term.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available