Participation of Neurohypophysial Hormone in Oviposition in the Hen

Abstract

Posterior lobes of pituitary were removed from White Leghorn hens before and after oviposition (expulsion of egg), and their dilute acetic acid extracts were assayed for their activities on isolated rat uterus and on frog water balance. Both these activities significantly decreased at the time of oviposition. The contents of oxytocin and arginine vasotocin in the posterior lobe extracts were estimated by calculation, taking account of the potency ratios of the 2 hormones for the rat uterus and for the frog water balance. It became clear that the content of arginine vasotocin greatly decreased at the time of oviposition, while the content of oxytocin showed a little decrease. The oviposition in the hen may be caused by the prompt discharge of arginine vasotocin from the posterior lobe of pituitary.