5 research outputs found
Influence of ERĪ² selective agonism during the neonatal period on the sexual differentiation of the rat hypothalamic-pituitary-gonadal (HPG) axis
<p>Abstract</p> <p>Background</p> <p>It is well established that sexual differentiation of the rodent hypothalamic-pituitary-gonadal (HPG) axis is principally orchestrated by estrogen during the perinatal period. Here we sought to better characterize the mechanistic role the beta form of the estrogen receptor (ERĪ²) plays in this process.</p> <p>Methods</p> <p>To achieve this, we exposed neonatal female rats to three doses (0.5, 1 and 2 mg/kg) of the ERĪ² selective agonist diarylpropionitrile (DPN) using estradiol benzoate (EB) as a positive control. Measures included day of vaginal opening, estrous cycle quality, GnRH and Fos co-localization following ovariectomy and hormone priming, circulating luteinizing hormone (LH) levels and quantification of hypothalamic kisspeptin immunoreactivity. A second set of females was then neonatally exposed to DPN, the ERĪ± agonist propyl-pyrazole-triol (PPT), DPN+PPT, or EB to compare the impact of ERĪ± and ERĪ² selective agonism on kisspeptin gene expression in pre- and post-pubescent females.</p> <p>Results</p> <p>All three DPN doses significantly advanced the day of vaginal opening and induced premature anestrus. GnRH and Fos co-labeling, a marker of GnRH activation, following ovariectomy and hormone priming was reduced by approximately half at all doses; the magnitude of which was not as large as with EB or what we have previously observed with the ERĪ± agonist PPT. LH levels were also correspondingly lower, compared to control females. No impact of DPN was observed on the density of kisspeptin immunoreactive (-ir) fibers or cell bodies in the arcuate (ARC) nucleus, and kisspeptin-ir was only significantly reduced by the middle (1 mg/kg) DPN dose in the preoptic region. The second experiment revealed that EB, PPT and the combination of DPN+PPT significantly abrogated preoptic Kiss1 expression at both ages but ARC expression was only reduced by EB.</p> <p>Conclusion</p> <p>Our results indicate that selective agonism of ERĪ² is not sufficient to completely achieve male-typical HPG organization observed with EB or an ERĪ± agonist.</p