INITIATION OF THE SPAWNING REFLEX RESPONSE IN FUNDULUS BY THE ADMINISTRATION OF FISH AND MAMMALIAN NEUROHYPOPHYSIAL PREPARATIONS AND SYNTHETIC OXYTOCIN

Abstract

Preparation of partially purified fish and beef pituitary protein fractions that are rich in fish spawning reflex activity is described. A method of assay of spawning reflex activity, based on the minimum dose that will elicit a response within 40 minutes, is described and a Fundulus unit is defined. Spawning reflex response can be elicited with purified natural arginine vaso-pressin, purified natural oxytocin, and synthetic oxytocin at approximately similar dosage levels (20-60 milliunits/ g weight, on the 40-minute assay). Fish and beef pituitary preparations with spawning reflex activity contain both oxytocic and vaso-pressor activity in approximate proportion to their spawning reflex assay.