Arginine vasotocin has an activity for the contraction of the hen's uterus (shell gland)1, 2), and its contents in the posterior lobe of pituitary decrease3) while the contents in the blood increase4-7) during normal oviposition.
Premature oviposition is induced by placing a thread in the wall of the uterus8-11) or by intrauterine injection of phosphate solution12). It is assumed that the premature oviposition may be related to an inhibition of shell calcification and to a sudden increase of phosphate levels in the uterine fluid11-13). However, it is unknown whether the premature oviposition is mediated by the release of vasotocin from the pituitary.
The present study was designed to investigate the change in the vasotocin activity in the blood during normal and premature ovipositions.