Dynorphin-Kappa Opioid Receptor Signaling Partly Mediates Estrogen Negative
Feedback Effect on LH Pulses in Female Rats |
| |
Authors: | Mst Parvin MOSTARI Nahoko IEDA Chikaya DEURA Shiori MINABE Shunji YAMADA Yoshihisa UENOYAMA Kei-ichiro MAEDA Hiroko TSUKAMURA |
| |
Institution: | 1)Laboratory of Reproductive Science, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan;2)Laboratory of Animal Breeding, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan |
| |
Abstract: | Accumulating evidence suggests that the arcuate nucleus (ARC) kisspeptin/neurokinin B
(NKB)/dynorphin (KNDy) neurons play a role in estrogen negative feedback action on
pulsatile gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) release. The
present study aimed to determine if dynorphin (Dyn) is involved in estrogen negative
feedback on pulsatile GnRH/LH release. The effect of the injection of nor-binaltorphimine
(nor-BNI), a kappa-opioid receptor (KOR) antagonist, into the third cerebroventricle (3V)
on LH pulses was determined in ovariectomized (OVX) adult female rats with/without
replacement of negative feedback levels of estradiol (low E2). The mean LH
concentrations and baseline levels of LH secretion in nor-BNI-injected, low
E2-treated rats were significantly higher compared with vehicle-treated
controls. On the other hand, the nor-BNI treatment failed to affect any LH pulse
parameters in OVX rats without low E2 treatment. These results suggest that Dyn
is involved in the estrogen negative feedback regulation of pulsatile GnRH/LH release. The
low E2 treatment had no significant effect on the numbers of ARC
Pdyn (Dyn gene)-,Kiss1- and
Tac2 (NKB gene)-expressing cells. The treatment also did not affect
mRNA levels of Pdyn and Oprk1 (KOR gene) in the
ARC-median eminence region, but significantly increased the ARC kisspeptin
immunoreactivity. These findings suggest that the negative feedback level of estrogen
suppresses kisspeptin release from the ARC KNDy neurons through an unknown mechanism
without affecting the Dyn and KOR expressions in the ARC. Taken together, the present
result suggests that Dyn-KOR signaling is a part of estrogen negative feedback action on
GnRH/LH pulses by reducing the kisspeptin release in female rats. |
| |
Keywords: | Arcuate nucleus GnRH Kisspeptin Neurokinin B |
|
|