Circadian Regulation of Kisspeptin in Female Reproductive Functioning - Kisspeptin Signaling in Reproductive Biology - page 385

Fig. 18.5 Circadian Kiss1 expression is coupled to an oscillator within the dorsomedial SCN.
( a ) Kiss1 expression on misaligned days 1 h before dmSCN-associated activity onset, but not 1 h
before the vlSCN-associated locomotor activity onset, is similar to that in aligned animals before
the locomotor activity onset [one way ANOVA ( P = 0.05)]. Bars, mean ± SEM; groups not sharing
the same capital letter are statistically signifi cant according to Tukey post hoc comparisons
( P = 0.05). Asterisk , signifi cantly different from aligned and misaligned taken together, planned
comparison, P = 0.02. ( b ) Representative Kiss1 ISH autoradiographic fi lms from animals killed on
aligned days just before locomotor activity onset and on misaligned days just before dmSCN-
associated activity onset (dm) or just before the vlSCN-associated activity onset (vl). From Smarr
BL, Morris E, de la Iglesia HO. The Dorsomedial Suprachiasmatic Nucleus Times Circadian
Expression of Kiss1 and the Luteinizing Hormone Surge. Endocrinology. 2012. Epub 2012/03/29.
Reprinted with permission from The Endocrine Society
manner to AVP stimulation and (2) if GnRH neurons display time-dependent
sensitivity to kisspeptin signaling. If time-dependent sensitivity is controlled at the
level of the AVPV, then one would expect kisspeptin cells to exhibit daily changes
in sensitivity to AVP stimulation and contain an endogenous time-keeping
mechanism. Alternatively, if the gating of control occurs within GnRH cells, then
one would expect the GnRH system to display daily sensitivity in response to both
AVP and kisspeptin administration. Our fi ndings indicate that the kisspeptin system
responds indiscriminately to AVP administration, regardless of time of day, whereas
the GnRH system is only sensitive to kisspeptin stimulation at the time that the
surge would normally occur (Fig. 18.6 ) [ 54 ]. These results further support the
notion that kisspeptin cells do not keep circadian time but, instead, that their activity
is driven by AVPergic SCN cells. However, these fi ndings point to an important role
for autonomous circadian oscillators in GnRH cells underlying time-dependent