PHARMACOLOGICAL CHARACTERISTICS OF THE ACTIVE PRINCIPLES IN NEUROHYPOPHYSIAL EXTRACTS FROM SEVERAL SPECIES OF FISHES1

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Abstract
Pituitary extracts from a marine teleost (Pollachius virens), a cyclostome (Petromyzon marinus) and an elasmobranch (Squalus acanthias) have been subjected to a variety of biological assays. The activities of these extracts have been determined on rat blood pressure, rat antidiuresis, rat uterus in vitro, rabbit milk ejection, fowl blood pressure, the hen oviduct in vitro and the bullfrog bladder in vitro. The patterns of relative activities on these assays for each species have been compared to the patterns for known neurohypophysial hormones and related synthetic analogues. The evidence suggests that arginine vasotocin (8-arginine oxytocin) is the major active neurohypophysial peptide in the teleost and cyclostome. Oxytocin also appears to be present in the teleost. The neurointermediate lobe of the elasmobranch contains a pattern of activities that cannot be readily attributed to any of the known neurohypophysial peptides or synthetic analogues that have been examined to date.