Biology Reference
In-Depth Information
Table 3.3
Percentage of ARC kisspeptin cells co-localizing other neuropeptides/transmitters
Species
NKB
Dyn
Galanin
Met-Enk
Glutamate
GABA
Human
77 [
44
]
Rhesus monkey
40-60
a
Mouse
90
b
, 94
c
92
b
, 86
c
12
d
, 65
e
0
e
90 [
55
]
50 [
55
]
Rat
97 [
107
]
Sheep
80
f
94
f
Goat
99 [
38
]
78 [
38
]
a
Castrated males [
40
]
b
OVX [
63
]
c
Castrated and castrated + T males [
61
]
d
OVX [
106
]
e
Intact mice treated with colchicines [
67
]
f
OVX + E [
10
]
In addition to medially located nuclei, in the mouse, rat, and human hypothala-
mus, a few kisspeptin fi bers are also seen consistently in the lateral preoptic and
lateral hypothalamic areas (Table
3.2
). Rostrally, kisspeptin-immunoreactive fi bers
in these species are present in a variety of forebrain structures, including the medial
and lateral septum, the diagonal band of Broca, and organum vasculosum of the
lamina terminalis (OVLT). Finally, in mice and rats, kisspeptin fi bers have been
reported in the caudal hypothalamus, and in mice also in more distant locations: the
periaqueductal gray of the midbrain, the locus coeruleus, the paraventricular nucleus
of the thalamus, as well as the medial amygdala (Table
3.2
). Whether kisspeptin
fi bers in these more widespread areas are seen in other species is not known.
Likewise, the precise origin of these fi bers remains to be determined; while some
are likely to arise from the ARC or RP3V kisspeptin cells (see section
Anatomical
Connections of Kisspeptin Cells
), it is possible that others originate from popula-
tions located outside of the hypothalamus (see above).
Co-localization of Other Peptide/Transmitters
There is increasing evidence of anatomical heterogeneity among kisspeptin cell
populations, specifi cally with respect to their co-expression of other neuropeptides
and neurotransmitters. The most consistent example of this to date is in the ARC
population, where a majority of kisspeptin neurons express two other neuropep-
tides, neurokinin B and dynorphin, each of which has been strongly implicated in
the physiological control of GnRH secretion [
58
,
59
]. The high degree of co-
localization of kisspeptin, NKB, and dynorphin in the ARC population (Table
3.3
)
and its conservation across species (Fig.
3.1
) has led to the acronym “KNDy”
neurons [
60
]. KNDy cells form reciprocal connections with each other, as well as
project to GnRH neurons, and the combination of excitatory (kisspeptin, NKB) and
inhibitory (dynorphin) actions within this circuitry has provided the foundation for
models of how this kisspeptin population may be involved in the generation and
control of GnRH pulses [
38
,
60
-
62
]. Although the percentage of KNDy peptide
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