(A, B) Hemi-hypothalamic coronal sections through the region of the pre-mammilary nucleus (PrM) and posterior arcuate nucleus (Arc) of castrate adult male monkeys showing of a cluster of periventricular substance P (SP) neurons dorsal to the Arc in the region of the PrM revealed with the Eskay antibody using Ni-DAB (A) and immunofluorescence (B; confocal projection 10×; 1 µm optical sections). (C) Schematic diagram of a coronal hemi-section of the posterior medial basal hypothalamus (MBH) of the rhesus monkey [54, permission pending] depicting the distribution of Arc and non- Arc SP cells (red dots) and their relationship to kisspeptin neurons (green dots). (D) Distribution of non-Arc SP neurons in intact (open bar, n=4) and castrate (closed bar, n=4) adult male monkeys. Immunopositive SP neurons were enumerated in a series of hemi-sections at 500 µm intervals throughout the MBH. As in Fig. 5, the distributions of SP neurons are aligned to the section with the greatest number of Arc kisspeptin neurons (indicated as 0 on the abscissa). (E), Non significant effect of castration on number (mean±SEM) of immunopositive non-Arc SP neurons (open bar, intacts; closed bar, castrates). Scale bar, 50µm.