Archive for the 'Ovariectomized' Category

10 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(8)

Ovariectomized ewes show an increase in pulse amplitude during the nonbreeding season, but in contrast pulse amplitude declined in the current experiment. The role of thyroid hormones in seasonal LH secretion in the ewe in the absence of gonadal steroids has received no direct attention; however, the results of Moenter et al. suggest that pulse […]

09 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(7)

Taken together with the absence of LH responses to dopaminerg-ic-D2 receptor agonists and antagonists in experiment 1, our results indicate that the mechanisms contributing to seasonal breeding in the ovariectomized, estradiol-treated red deer hind operate differently from those in the ewe. A limitation of this conclusion, however, is our current inability to measure estradiol reliably […]

08 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(6)

This is in contrast to the growing body of evidence for the ewe, in which the thyroid gland has been shown to be required for the profound increase in estradiol negative feedback that occurs at the end of the breeding season. Episodic LH secretion characteristics in ovariectomized estradiol-treated hinds in experiment 1 differed from those […]

07 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(5)

As was noted previously in relation to bromocriptine and sulpiride, the prolactin responses to morphine and naloxone in the current experiment confirm that the dosages used were sufficient to elicit biological responses in this species. However, the response observed in our hinds was not the same as has been reported in studies of sheep, in […]

06 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(4)

Neural pathways that are not activated by gonadal steroids are of particular significance to red deer reproduction since they appear to make a much larger contribution to seasonal breeding in this species than in the ewe. Therefore, in experiment 2 we examined the role of endogenous opioid peptides, as these appear to have an inhibitory […]

05 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(3)

Although prolactin responses do not necessarily prove that the dose of drug used was sufficient to affect dopa-minergic-D2 receptor-mediated pathways that mediate GnRH secretion, they do at least show that the drug treatments were effective in binding to dopaminergic-D2 receptors and evoking an appropriate biological response. Second, we have given bromocriptine at five times the […]

04 Mar

Pulsatile Luteinizing Hormone Secretion in the Ovariectomized: DISCUSSION(2)

Although the results of these studies may initially appear to be comparable to the results of experiment 1, it must be noted that whereas sulpiride is a specific dopami-nergic-D2 antagonist, pimozide is less specific for these receptors and binds also to dopaminergic-Dj receptors in the brain. In a comparative study of the two drugs, sulpiride […]

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