Kisspeptin and GnRH Pulse Generation - Kisspeptin Signaling in Reproductive Biology - page 300

Fig. 14.5 Effects of KOR agonist or antagonist on the MUA and LH secretion in an OVX goat.
( a ) Representative profi les of the MUA and plasma LH concentrations in an OVX goat that received
a bolus icv injection of Dyn at the indicated time point. ( b ) Representative profi les of the MUA and
plasma LH concentrations in the goat that received icv infusion of KOR antagonist (nor-BNI) for
2 h. ( c ) Changes in the intervolley interval and volley duration before (Pre, blank bar ) and during
( solid bar ) the nor-BNI infusion periods. Values are expressed as mean±SEM in four goats.
** p < 0.01, * p < 0.05 compared with respective Pre values. Reproduced from Wakabayashi Y, et al.
Neurokinin B and dynorphin A in kisspeptin neurons of the arcuate nucleus participate in generation
of periodic oscillation of neural activity driving pulsatile gonadotropin-releasing hormone secretion
in the goat. J Neurosci. 2010 Feb 24;30(8):3124-32. With permission from Journal of Neuroscience
other species [ 100 - 102 ], whereas the occurrence of MUA volleys was unchanged
[ 103 ]. Furthermore, the expression of Kiss1r was not detected in KNDy neurons
[ 75 , 104 ]. These results suggest that kisspeptin/Kiss1r signaling is not involved in
the GnRH pulse-generating mechanism per se. However, fi bers surrounding KNDy
neurons contain not only NKB and Dyn [ 53 , 62 , 63 , 105 ] but also kisspeptin [ 54 , 86 ,
106 ]. Moreover, treatment with a kisspeptin antagonist into the ARC suppresses
pulsatile LH secretion [ 107 ]. Therefore, the possibility that kisspeptin may have
some functions in the control of GnRH/LH secretion by acting on other cells than
KNDy neurons still cannot be ruled out. However, it is also likely that the kisspeptin
antagonist treatment did not affect the GnRH pulse generator, but rather diffused to
the median eminence where it was able to block kisspeptin stimulation of GnRH
fi bers, resulting in suppressed LH secretion.