Occurrence of Urotensin II (Bladder-Contracting Activity) in the Caudal Spinal Cord of Anamniote Vertebrates

1 Urotensin II (bladder-contracting activity) is present in the caudal spinal cords of teleosts, elasmobranchs, holosteans, and chondrosteans, in order of decreasing activity. It is questionably present in holocephalans and probably absent from lungfishes. 2 Cyclostomes and tailed amphibians show no evidence for any specific caudal urotensin II. 3 The pharmacological evidence parallels the cytological evidence for the occurrence of a caudal neurosecretory system.