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murine brain, the results must be interpreted conservatively until confi rmed with
conventional ISH or ICC.
Hypothalamic Expression
Even with these caveats in mind, some clear general patterns emerge when
Kiss1r
expression in the hypothalamus is examined across species. In all species studied,
there is clear
Kiss1r
expression in the POA (Table
3.5
). In monkeys [
42
,
79
,
80
], rats
[
22
,
81
-
84
], and mice [
85
],
Kiss1r
was identifi ed using RT-PCR of tissue block
extracts, and many of the latter studies used microdissected POA tissue [
81
,
82
,
84
,
85
]. Moreover, this conclusion is supported by ISH data in sheep [
35
,
86
,
87
], rats
[
20
], and mice [
13
,
78
,
88
], which also demonstrated co-localization of
Kiss1r
in
GnRH neurons (Table
3.5
).
The second relatively consistent location of
Kiss1r
within the hypothalamus is
in the ARC (Table
3.5
).
Kiss1r
mRNA has been found in the ARC using both
RT-PCR in rats [
22
,
81
-
84
] and mice [
85
], and ISH in sheep [
86
] and rats [
77
]; it
is also likely that the
Kiss1r
found in the MBH of monkeys [
42
,
79
,
80
] also
refl ects, in part, expression in the ARC. In contrast, no
Kiss1r
expression was
found in mice using Xgal ICC [
78
], but this observation needs to be confi rmed
using other approaches since
Kiss1r
was readily detectable in micropunches of the
murine ARC [
85
]. There are two consistent reports of
Kiss1r
in the posterior hypo-
thalamus of rats [
77
] and mice [
78
] and in the RP3V of rats [
83
,
84
], although it
was not observed in the latter area in mice using Xgal ICC [
78
]. Similarly, this
receptor has been observed in the AHA, DMH, LHA, ventral premammillary
nuclei, and zona incerta of rats [
77
], but not mice [
78
]; whether this refl ects species
or technical differences awaits further work.
Extra-hypothalamic Expression
There is even less data on expression of
Kiss1r
in areas outside the hypothalamus,
and the only species in which there is information on other neural areas are rats [
77
],
mice [
78
], and humans [
75
,
76
]. As noted above, the latter comes from two early
reports using RT-PCR before the role of
Kiss1r
in reproduction had been discov-
ered. The highest levels of
Kiss1r
are consistently found in the hippocampus, with
relatively high expression also observed in the amygdala (humans and rats), periaq-
ueductal gray (rats, mice), and locus coeruleus (humans, rats). Relatively high
expression of
Kiss1r
was also reported in the supramammillary nuclei of mice, but
data on this region is not available for other species. Similarly, there is evidence for
Kiss1r
expression in the primary olfactory cortex of rats, and the caudate nucleus of
humans that is not available in other species. Finally, there are a number of reports
that
Kiss1r
is found in the anterior pituitary of humans [
75
], baboons [
89
], sheep [
90
,
91
], pigs [
92
], and rats [
93
,
94
]. One of these studies observed that co-localization
in the rat pituitary was limited to gonadotropes using dual ICC [
94
], but there was
no differential expression of
Kiss1r
in cellular fractions of ovine pituitary enriched
for gonadotropes, compared to fractions enriched for somatotropes or lactotropes
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