CSF reabsorption routes in the adult rat as revealed by recovered 125-labeled human serum albumin (HSA) in lymph nodes: Anesthetized male adult Wistar rats (n = 8) were killed 6 hr after 125I-HSA injection into lateral ventricle. HSA uptakes were averaged for bilateral and multiple nodes. Symbols indicate differences (P < 0.05) in test node activity relative to spleen (*) or popliteal (#) lymph nodes. Head and lymph node activities greater than spleen indicate tracer passage from CSF directly to submaxillary or cervical nodes. Lumbar node activity was above the spleen and popliteal nodes (not expected for direct CSF drainage). Reproduced with permission from M. Johnston and the American Journal of Physiology .