Testicular histology following a single s.c. injection of 50 nmol kisspeptin-54 or GnRH in the adult rat. Testicular histology was assessed 24 h following injection. Cross sections of testicular tubules assessed by light microscopy on H&E-stained sections from rats treated with single s.c. injection of (A & B) saline, (C & D) kisspeptin-54 (50 nmol) or (E & F) GnRH (50 nmol). (A) Representative section from a control animal showing tubules with normal maturation to late-stage elongated spermatids and a few spermatozoa. (B) Higher magnification of (A) to show a single tubule. (C) Representative section of an animal treated with a single s.c. injection of 50 nmol kisspeptin-54 showing severe testicular degeneration. (D) Higher magnification of (C) to show a tubule with severe necrotic degeneration and atrophy of the germinal cells (asterisk), degeneration characterized by multinucleated giant cells (m, arrow) and apoptotic cells (a, arrow). (E & F) Representative section of an animal treated with a single s.c. injection of 50 nmol GnRH showing the same features as described for kisspeptin-54 in C & D. (A, C & E: Original magnifications ×100. Scale bar represents 100 µm. B, D & F: Original magnifications ×400. Scale bar represents 25 µm). GnRH, gonadotrophin-releasing hormone; H&E, haematoxylin and eosin.