Strain differences in the expression of corticotropin-releasing hormone immunoreactivity in nerves that supply the spleen and thymus

The existence of nerve fibers containing corticotropin-releasing hormone (C RH) immunoreactivity in primary and secondary lymphoid organs from three st rains of young adult male rats was examined. Spleens and thymuses from Fisc her 344 (F344), Sprague-Dawley (SD) and Lewis (LEW) rats were prepared for immunocytochemistry using antisera directed against CRH. In F344 and SD rat s, we were unable to demonstrate CRH-immunoreactive nerves in either the th ymus or the spleen. Despite the lack of CRH-containing nerves, CRH immunore activity was present in pleotropic cells in the septum, cortex and medulla of the thymus, and in the red and white pulp of spleens from F344 and SD ra ts. In contrast, CRH+ nerves were found in thymuses and spleens from LEW ra ts. CRH+ nerves coursed in the interlobular septa, capsule, cortex and medu lla of the LEW rat thymus. Large CRH-immunoreactive nerve bundles were pres ent in the hilar region of the LEW rat spleen, and individual CRH+ fibers c oursed in the capsule, trabeculae, red pulp, venous sinuses and marginal zo ne of the white pulp of the spleen. These findings indicate strain differen ces in neurotransmitter-specific nerves that innervate the rat spleen and t hymus under basal conditions. Copyright (C) 2001 S. Karger AG, Basel.