In ruminants, the preoptic area (POA) and arcuate (ARC) are the main hypothalamic nuclei through which kisspeptin influences gonadotropin releasing hormone (GnRH) neurons for reproductive functions. The relationship between kisspeptin and GnRH releasing in many species has been studied, but not in buffalo. The aims of this study were to detect the localization of Kiss-1 mRNA and the distribution of kisspeptin protein in the POA and ARC hypothalamic nuclei of cycling buffalo cows. Brains were collected from 6 buffaloes and processed for paraffin blocks. Four-micron paraffin sections of the POA and ARC hypothalamic nuclei were prepared for (1) chromogenic in situ hybridization using a Kiss-1cRNA probe designed from the ovine kisspeptin gene sequence (GenBank accession no. DQ059506) and (2) immunohistochemistry using a rabbit anti-mouse kisspeptin-10 antibody. The signals for Kiss-1 mRNA and the localization of kisspeptin proteins were detected in the cytoplasm of the POA and ARC neuronal soma and some small neuronal cells.  Kisspeptin proteins were also found in the cellular process of the POA and ARC neurons. The population of kisspeptin-immunoreactive neurons distributed in the POA (79.8±2.5%) was greater than in the ARC area (62.5±4.5%) (P≤0.01). This study provides evidence of Kiss-1 mRNA and kisspeptin protein in the hypothalamus of buffalo, and it will hopefully help lay the groundwork for a further understanding of the role of kisspeptin in buffalo and its relation to reproduction and the hypothalamic- pituitary- gonadal axis.

Key words: Buffalo, Hypothalamus, In situ hybridization, Kiss-1, Kisspeptin