The mechanisms by which aging progressively depletes testosterone (Te) availability in the male are unknown. Accordingly, the objective was to estimate brain gonadotropin-releasing hormone (GnRH) outflow (release and action), which cannot be observed directly, on the basis of downstream effects on pituitary luteinizing hormone (LH) secretion. LH, in turn, feeds forward on (stimulates) gonadal T...

Copyright: © 2012 Asimakopoulos B. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The structure and the function of the Hypothalamus-PituitaryGonadal (HPG) axis is an integral part of the knowledge on the phy...

Seasonal reproduction in birds is the adaptation to breed at the time of the greatest survival of young. This exact moment is mainly imposed by the photoperiod which stimulates the hypothalamo-pituitary-gonadal axis and starts breeding season. This article summarizes present knowledge concerning: 1/ perception and transduction of light into the biological signal; 2/ model of the avian photoperi...

The present thesis deals with different aspects of population pharmacokinetic/ pharmacodynamic (PK/PD) modelling of the male hypothalamic-pituitary-gonadal (HPG) axis. The thesis consists of a summary report and five scientific research papers. An overview of the main topics covered in the thesis is provided in the summary report including PK/PD modelling in drug development, the pathological, ...

Reproductive function depends upon an operational hypothalamo–pituitary–gonadal (HPG) axis. Due to its role in determining survival versus reproductive strategies, the HPG axis is vulnerable a diverse plethora of signals that ultimately manifest with Central Hypogonadism (CH) all many guises. Acquired CH can result from any pituitary or hypothalamic lesion, including treatment (such as surgical...

Recent evidence indicates that transthyretin (TTR), the major transport protein for thyroxine [1] and retinol binding protein [2], plays important roles in amyloidβ (Aβ) metabolism. Transthyretin has been demonstrated to bind Aβ in vitro [3,4] and in vivo [5,6], colocalize in Aβ plaques and within neurons containing intracellular Aβ [7], and recent evidence suggests it might act as a transport ...

The distribution of orexin A-immunoreactive neurons and orexin type I receptors in the CNS suggests important roles in regulating the hypothalamo-pituitary gonadal (HPG) axis and sexual behaviors. We examined orexin A interactions in the HPG axis in vivo and in vitro. Orexin A stimulated LH-releasing hormone (LHRH) release in hypothalamic explants harvested from male rats (+133%) and from femal...

Tachykinins play a critical role in neuroendocrine regulation of reproduction. The best known members of the family are substance P (SP), neurokinin A and neurokinin B. Tachykinins mediate their biological actions through three G protein-coupled receptors, named NK1, NK2, and NK3. SP was suggested to play an important role in the ovulatory process in mammals and humans. Recent findings suggest ...