Localization of kisspeptin neurons in the hypothalamus of peripubertal female lambs; possible connection with gonadotrophin releasing hormone and neuropeptide Y neurons

The effect of short fasting on the hypothalamic neuronal system of kisspeptin in peripubertal female lambs

“…This phenomenon is likely due to decrease in neuronal transport of kp rather than its increased release, because the kp synthesis in ARC perikarya in fasting conditions is suppressed. For sheep and monkeys, it was demonstrated that kp-terminals closely overlap the GnRH nerve terminals in the lateral zone of the ME (Polkowska et al, 2014;Ramaswamy et al, 2008). This neuro-anatomical connection between kp and GnRH neurons suggests that the essential role of kp in generating the GnRH/LH surge takes place at the level of GnRH release.…”

“…We have shown that fasting influenced both, rostral (AP) and ARC population of kp neurons. However, we evaluated the kp expression only in ARC population, because in peripubertal sheep the rostral set of kp neurons in AP is scarce and hardly detectable by immunohistochemistry (Nestor et al, 2009;Polkowska et al, 2014).…”

“…In this indirect mechanism, such factors as some orexigenic peptides of the central nervous system have been implicated, which are responsible for both, the control of energy balance and reproduction. For example, recent studies have established associations between kp cells and neuropeptide Y (Backholer et al, 2010;Polkowska et al, 2014) and proopiomelanocortin cells (Backholer et al, 2010). In sheep, about 80% of ARC kp cells co-localize with neurokinin B and 94% with dynorphin A and their axons have direct membrane contact with GnRH axons in the ME (Goodman et al, 2007).…”

The timing of puberty (oocyte quality and management)

“…In the prepubertal ewe, NPY stimulates the expression of Lhb (β-LH subunit) in gonadotrope cells (Wańkowska and Polkowska, 2009). Neuroanatomical studies in prepubertal ewes demonstrate the presence of NPY inputs on Kp neurons in the ArcN (Polkowska et al, 2014) and on GnRH neurons in the POA (Norgren and Lehman, 1989;Tillet et al, 1989), thus suggesting two distinct pathways that can be involved in the stimulatory effect of NPY. The existence of 5 NPY receptors subtypes coupled to various signaling pathways and the existence of different hypothalamic and pituitary targets, can account for such opposite effects observed according to the sex, the steroid environment and the physiological state (Pralong, 2010).…”