Biology Reference
In-Depth Information
Fig. 14.3
Dual labeling of kisspeptin and NKB in the E2-treated OVX goat. Photomicrographs of
sections of the POA (
a
-
c
) or ME (
d
-
f
) immunostained for kisspeptin (
a
and
d
) and NKB (
b
and
e
).
(
c
,
f
) are computer-aided merged images of (
a
) and (
b
), or (
d
) and (
e
), respectively. The
arrows
in
(
a
) and (
c
) indicate cell bodies containing exclusively kisspeptin immunoreactivity. The
green
,
red
,
and
yellow arrowheads
show kisspeptin, NKB, and kisspeptin/NKB positive fi bers. Note that a
majority of kisspeptin positive fi bers contain NKB immunoreactivity (
f
) at the ME.
MEe
the external
layer of the ME;
pt
pars tuberalis. Scale bar: 50
ยต
m
Roles of NKB/NK3R, Dyn/KOR, and Kisspeptin/Kiss1r
Signaling Pathways in the GnRH Pulse Generation
NKB/NK3R Signaling
The involvement of NKB in the control of GnRH/LH secretion was initially
proposed based on morphological changes in NKB neurons in the ARC (the
infundibular nucleus in primates) of postmenopausal women and experimental
animals [
67
,
83
]. The proposition is strongly supported by the fi nding that muta-
tions in either Tac3 or Tacr3 (which encode NKB and NK3R, respectively) cause
severe gonadotropin defi ciency in humans [
89
,
90
] and that Tacr3 null mice
show reduced gonadal activities, although they are not completely infertile [
91
].
Those studies predicted the stimulatory action of NKB on GnRH/LH secretion,
but initial reports provided a controversial view indicating that senktide (a selec-
tive NK3R agonist) decreased LH secretion in rats [
92
] and mice [
57
].
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