Distribution of kisspeptin (KP, A,C) and substance P (SP, B,D) immunopositive neurons in the arcuate nucleus (Arc) of intact (open bar, n=4) and castrate (closed bar, n=4) adult male monkeys. KP and SP neurons were enumerated in a series of hemi-sections taken at 500 µm intervals throughout the medial basal hypothalamus starting at the first retrochiasmatic section. In A and B, the distribution of both peptides in each group of animals was aligned to the section containing the highest number of KP neurons (indicated as 0 on the abscissa). C and D, comparison of the sum (mean±SEM) of KP (C) and SP (D) neurons counted in the hemi-sections analysed. *** P<0.001 and *P <0.05.