Kisspeptin photometry recordings during pregnancy and lactation

The specific role that prolactin plays in lactational infertility, as
distinct from other suckling or metabolic cues, remains unresolved. Here,
deletion of the prolactin receptor (Prlr) from forebrain neurons or
arcuate kisspeptin neurons resulted infailure to maintain normal
lactation-induced suppression of estrous cycles. Kisspeptin
immunoreactivity and pulsatile LH secretion were increased in these mice,
even in the presence of ongoing suckling stimulation and lactation. GCaMP
fibre photometry of arcuate kisspeptin neurons revealed that the normal
episodic activity of these neurons is rapidly suppressed in pregnancy and
this was maintained throughout early lactation. Deletion of Prlr from
arcuate kisspeptin neurons resulted in early reactivation of episodic
activity of kisspeptin neurons prior to a premature return of reproductive
cycles in early lactation. These observations show dynamic variation in
arcuate kisspeptin neuronal activity associated with the hormonal changes
of pregnancy and lactation, and provide direct evidence that prolactin
action on arcuate kisspeptin neurons is necessary for suppressing
fertility during lactation in mice.