Elucidating the physiological mechanisms that control reproduction is an obvious 
strategy for improving the fertility of cattle and developing new agents to 
control reproductive functions. The present study aimed to identify kisspeptin 
neurons in the bovine hypothalamus, clarifying that a central mechanism is also 
present in the cattle brain, as kisspeptin is known to play an important role in 
the stimulation of gonadotropin-releasing hormone (GnRH)/gonadotropin secretion 
in other mammals. To characterize kisspeptin neurons in the bovine hypothalamus, 
the co-localizations of kisspeptin and neurokinin B (NKB) or kisspeptin and 
dynorphin A (Dyn) were examined. Hypothalamic tissue was collected from Japanese 
Black or Japanese Black × Holstein crossbred cows during the follicular and 
luteal phases. Brain sections, including the arcuate nucleus (ARC) and the 
preoptic area (POA), were dual immunostained with kisspeptin and either NKB or 
Dyn. In the ARC, both NKB and Dyn were co-localized in kisspeptin neurons during 
both the follicular and luteal phases, demonstrating the presence of 
kisspeptin/NKB/Dyn-containing neurons, referred to as KNDy neurons, in cows. In 
the POA, no co-localization of kisspeptin with either NKB or Dyn was detected. 
Kisspeptin expression in the follicular phase was higher than that in the luteal 
phase, suggesting that kisspeptin expression in the POA is positively controlled 
by estrogen in cows. The kisspeptin neuronal populations in the ARC and POA 
likely play important roles in regulating the GnRH pulse and surge, 
respectively, in cows.