English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

In this paper the problem of the hypothalamic centres involved in the control of gonadotrophin secretion will be presented, based on investigations performed on rats and sheep. The data obtained for the rat were chosen because the control of gonadotrophin secretion in this animal is best known, and therefore this animal may be considered as a model to be compared with the others. On the other hand, the sheep, retaining seasonality of reproductive processes, represents the most natural model of reproduction among farm animals. According to earlier concepts, the release of gonadotrophins from the pituitary gland was supposed to be under hypothalamic control displayed at two levels: the medial basal hypo¬ thalamus (MBH) was claimed to produce gonadotrophic releasing hormones (Gn-RHs) and mediate the tonic secretion of gonadotrophins, whereas the preoptic anterior hypothalamic area (PAHA) was thought to initiate phasic, preovulatory release of gonadotrophins and was considered to be the 'regulatory centre' of this process. Evidence for this hypothesis emerged mainly from investigations carried out on rats (Flerko, 1970; Barraclough, 1973) and also partly on sheep (Przekop & Domanski, 1970). The results obtained from other species were not in accordance with this hypothesis. On the basis of our present knowledge it may be said that the hypothesis of hypothalamic regulation at two levels does not agree with recent findings concerning the site of LH-RH production in rats and sheep and a so-called 'regulatory' centre in rats.

Hypothalamic centres involved in the control of gonadotrophin secretion