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Table 3.4
Percentage of RP3V or POA kisspeptin cells co-localizing other neuropeptides/
transmitters
Species
NKB
Dyn
Galanin
Met- Enk
TH
Glutamate
GABA
Mouse
10 [
63
]
33 [
63
]
87
a
, 7
b
28-38
b
51-68
c
, (80) [
65
]
20 [
55
]
75 [
55
]
Rat
5, 20-50
d
Sheep
0
e
0
e
0
e
Goat 0 [
36
]
a
OVX + E [
106
]
b
Intact mice treated with colchicine [
67
]: for Met-Enk, AVPV, 28%; PVpo, 38%
c
Diestrus 51-55%; proestrus 58-68% [
64
]
d
ICC: OVX + E <5%; ISH: OVX + E <20%, intact diestrus 30%, OVX 50% [
14
]
e
OVX + E [
10
]
Preoptic kisspeptin cells in sheep and goats do not appear to co-localize either
NKB or dynorphin, although a subset of RP3V neurons does appear to contain both
peptides in the mouse [
63
] (Table
3.4
); other species have not as yet been examined
for this possible co-localization. However, a sizeable percentage of RP3V cells in
both the mouse [
64
,
65
] and rat [
21
] appear to co-localize tyrosine hydroxylase
(TH) (Fig.
3.1d
), the rate-limiting enzyme for dopamine biosynthesis [
64
], although
the precise percentage in the rat appears to vary by steroidal status and by whether
double-label ICC or ISH was used (Table
3.4
). By contrast, kisspeptin cells in the
POA or ARC of the sheep do not contain TH [
66
] even though they are close to
adjacent dopaminergic neurons in both regions. In addition, a sizable percentage of
RP3V kisspeptin cells in the mouse co-localize met-enkephalin (Fig.
3.1e
) and
some co-localize galanin [
67
]; KNDy neurons in the mouse also co-localize galanin
but not met-enkephalin (Table
3.3
).
In addition to co-localization of other peptides, cells of both the ARC and RP3V
kisspeptin populations contain the classical amino acid transmitters, glutamate and
GABA (Tables
3.3
and
3.4
), as revealed by co-localization of the markers, vesicular
glutamate transporter-2 (vGlut2) and gamma amino acid decarboxylase (GAD)-67,
respectively. However, the ARC population is predominantly glutamatergic,
whereas RP3V cells are mostly GABAergic [
55
]. Preliminary observations in the
sheep [
68
] suggest that this distinction between ARC and RP3V populations holds
in other mammals as well. Finally, it should be noted that kisspeptin cells located in
other regions (e.g., medial amygdala) have not yet been examined for possible
co- expression of other peptides or transmitters. Given the likely functional hetero-
geneity of these anatomically distributed populations, it seems probable that their
neurochemical phenotypes will be similarly diverse.
Co-localization of Steroid Receptors
The key role that kisspeptin cells play in the steroid feedback control of GnRH
neurons is underlined by the high degree of co-localization of nuclear receptors for
gonadal sex steroids in these cells. Indeed, in all species examined, a majority of both
ARC and RP3V/preoptic kisspeptin cells co-localize estrogen receptor (ER)-alpha
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