Rapid modulation of hypothalamic Kiss1 levels by the suckling stimulus in the lactating rat

Shimpei Higo
Satoko Aikawa
Norio Iijima
Hitoshi Ozawa

In mammals
 lactation suppresses GnRH/LH secretion resulting in transient infertility. In rats
 GnRH/LH secretion is rescued within 18-48 h after pup separation (PS) and rapidly re-suppressed by subsequent re-exposure of pups. To elucidate the mechanisms underlying these rapid modulations
 changes in the expression of kisspeptin
 a stimulator of GnRH secretion
 in several lactating conditions (normal-lactating; 4-h PS; 18-h PS; 4-h PS C1-h re-exposure of pups; non-lactating) were examined using in situ hybridization. PS for 4 h or 18 h increased Kiss1 expressing neurons in both the anteroventral periventricular nucleus (AVPV) and the arcuate nucleus (ARC)
 and subsequent exposure of pups re-suppressed Kiss1 in the AVPV. A change in Kiss1 expression was observed prior to the reported time of the change in GnRH/LH
 indicating that the change in GnRH/LH results from changes in kisspeptin. We further examined the mechanisms underlying the rapid modulation of Kiss1. We first investigated the possible involvement of ascending sensory input during the suckling stimulus. Injection of the anterograde tracer to the subparafascicular parvocellular nucleus (SPFpc) in the midbrain
 which relays the suckling stimulus
 revealed direct neuronal connections between the SPFpc and kisspeptin neurons in both the AVPV and ARC. We also examined the possible involvement of prolactin (PRL). Administration of PRL for 1 h suppressed Kiss1 expression in the AVPV but not in the ARC. These results indicate that suckling stimulus rapidly modulates Kiss1 expression directly via neuronal connections and indirectly through serum PRL
 resulting in modulation in GnRH/LH secretion.

JOURNAL OF ENDOCRINOLOGY

BIOSCIENTIFICA LTD

227

2

10.1530/JOE-15-0143

https://doi.org/10.1530/JOE-15-0143
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