Related Experiment Video
Updated: Oct 13, 2026
Determination of Reproductive Competence by Confirming Pubertal Onset and Performing a Fertility Assay in Mice and Rats
Published on: October 13, 2018
Peripubertal changes in the nature of the GnRH response to alpha-adrenoceptor stimulation in vitro and their
G Leposavic1, M R Dashwood, J Ginsburg
1Department of Pharmacology, Charing Cross and Westminster Medical School, London, UK.
Abstract:
Adrenergic mechanisms have been widely implicated in the regulation of GnRH secretion in adult rats but their role in young animals, in which the activity of the GnRH neurones is minimal, is unclear. These experiments were done to examine the effects of alpha-adrenoceptor stimulation on the secretion in vitro of GnRH by hypothalami from immature and adult male rats. The alpha 1-adrenoceptor agonist, phenylephrine (10(-9) - 10(-7) M), stimulated release of GnRH from hypothalami from adult (200 g) and peripubertal (150 g) rats but inhibited markedly the secretion of the releasing factor from the limited stores available in hypothalami from immature (50 or 100 g) rats. The stimulatory and inhibitory responses to phenylephrine, evident in adult and younger rats respectively, were concentration-dependent and antagonized readily by the selective alpha 1-adrenoceptor antagonist, alfuzosin (10(-6) M), but not by the beta-adrenoceptor antagonist, propranolol (10(-6) M). Hypothalami from 14-day castrated adult rats, in which the serum LH was elevated and hypothalamic GnRH content reduced, responded to alpha 1-adrenoceptor stimulation in vitro, like those from immature rats, with a marked reduction in GnRH release. In contrast, hypothalami from corresponding castrates bearing testosterone implants, which maintained the hypothalamic GnRH content and serum LH and testosterone concentrations at levels similar to those of intact controls, exhibited the normal 'adult' response to phenylephrine. Studies utilizing 3H-prazosin indicated that the number (Bmax) of hypothalamic alpha 1-adrenoceptor binding sites increases at puberty but that receptor affinity (KD) is unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
Related Concept Videos
01:09GPCRs Regulate Adenylyl Cylase Activity
Two...
01:31Adrenergic Receptors: ɑ Subtype
Adrenaline ≥ Noradrenaline >> Isoprenaline
α-adrenoceptors are further divided into α1 and α2-adrenoceptors.
α1-Adrenoceptors: These receptors are located postsynaptically on the effector organs and cause constriction of smooth muscle mediated by activation of phospholipase C—inositol-1,4,5-trisphosphate...
01:26Adrenergic Receptors: β Subtype
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors have equal affinities for...
01:22Target Cell Response to Hormones
Notably, the cellular response can be regulated by altering the number of receptors expressed in the cell. For example, prolonged exposure to elevated hormone levels results in a gradual decline or down-regulation in the number of receptors for that specific hormone on the cell surface. Conversely, in response to low hormone levels, cells may use up-regulation, producing an...
01:31Hormones of the Adrenal Glands
The adrenal cortex, a powerhouse of hormone synthesis, generates over two dozen corticosteroid hormones. The zona glomerulosa produces mineralocorticoids, exemplified by aldosterone, influencing the electrolyte composition of body fluids. The synthesis of glucocorticoids such as cortisol and corticosterone...
01:15Development of the Sexual Organs in the Embryo and Fetus
Near the gonadal ridges, two duct systems are present: the mesonephric ducts (Wolffian ducts) and paramesonephric ducts (Müllerian ducts). These ducts form the basis for the male...