Kisspeptin (KISS1; encoded by Kiss1) neurons in the arcuate nucleus (ARC) coexpress tachykinin 3 (TAC3; also known as neurokinin B) and dynorphin A (PDYN). Accordingly
they are termed KNDy neurons and considered to be crucial in generating pulsatile release of gonadotropin-releasing hormone. Accumulating evidence suggests that Kiss1 and Tac3 are negatively regulated by estrogen. However
it has not been fully determined whether and how estrogen modulates Pdyn and PDYN. Here
we examined the expression of Pdyn mRNA and PDYN by in situ hybridization and immunohistochemistry
respectively
in the ARC of female rats after ovariectomy (OVX) and OVX plus low-or high-dose beta-estradiol (E-2) replacement. We also investigated the effect of E-2 on expression of Kiss1
KISS1
Tac3
and TAC3. Furthermore
colocalization of PDYN and estrogen receptor alpha (ESR1) was determined. Subsequently
we found that low-dose E-2 treatment had no effect on Pdyn mRNA-expressing cells
but increased PDYN-immunoreactive (ir) cell numbers. In contrast
high-dose E-2 treatment resulted in prominent reductions in both Pdyn mRNA-expressing and PDYN-ir cell numbers. Changes induced by low or high doses of E-2 were similarly observed in the expression of Kiss1
KISS1
Tac3
and TAC3. The majority of PDYN-ir neurons coexpressed ESR1 in all groups. Our results indicate that E-2 regulates the expression of PDYN
as well as KISS1 and TAC3
with regulation by E-2 differing according to its levels.Summary SentenceEstrogen regulates dynorphin expression in the arcuate nucleus of female rats with low-dose estrogen suppressing dynorphin release and high-dose estrogen inhibiting dynorphin mRNA expression.
