The Influence of Hypophysectomy on the Time of Oviposition in Hens.

Abstract

FRAPS (1942) has first suggested, from the occurrence of premature ovulation resulted in the occurrence of premature oviposition , that there is a close relationship between oviposition and ovulation.The contraction of the uterine muscle which plays a main role in the expulsion of an egg from the uterus is observed whenever ovulation occurs regardless of the presence or the absence of an egg in the uterus (SHIMADA and ASAI,1978). The retained egg in the uterus by the short term vaginal ligation is expelled from the uterus in association with ovulation (NAKADA and TANAKA , 1990). These results adduce some additional evidence suggesting that the ovulation process participates in the regulation of oviposition.A presumption evolves that the time of midsequence oviposition which is commonly accompanied by the next ovulation may be delayed by preventing ovulation in hens. This study was made to examine the influence of removal of the anterior pituitary gland on the time of mid-sequence oviposition in the domestic fowl.(Jpn. Poult. Sci., 30: 306-309, 1993)

Sex, parturition and motherhood without oxytocin?

“…Indeed, it would have been brave to deny the likely truth of any part of this, for there have been many previous well-described examples of normal labour in humans and experimental animals with apparently complete posterior pituitary dysfunction (Amoroso & Porter 1966). Even in birds, egg laying has been observed to occur after acute neurohypophysectomy (Nakada et al 1993). With regard to other reproductive roles of oxytocin, it seems clear that species differences are considerable and obscure the interpretation of results from the knockout mouse.…”